Category Geology

This accurate, up-to-date map is created using digital technology. You can view GPS maps on your phone, tablet, or computer. They can tell you exactly where you are at any time. The coordinates and position as well as atomic time obtained by a terrestrial GPS receiver from GPS satellites orbiting Earth interact together to provide the digital mapping programming with points of origin in addition to the destination points needed to calculate distance. This information is then analyzed and compiled to create a map that provides the easiest and most efficient way to reach a destination.

More technically speaking, the device operates in the following manner:

• GPS receivers collect data from at least four GPS satellites orbiting the Earth, calculating position in three dimensions.
• The GPS receiver then utilizes position to provide GPS coordinates, or exact points of latitudinal and longitudinal direction from GPS satellites.
• The points, or coordinates, output an accurate range between approximately “10-20 meters” of the actual location.
• The beginning point, entered via GPS coordinates, and the ending point, (address or coordinates) input by the user, are then entered into the digital mapping software.
• The mapping software outputs a real-time visual representation of the route. The map then moves along the path of the driver.
• If the driver drifts from the designated route, the navigation system will use the current coordinates to recalculate a route to the destination location.

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A political map shows you the countries of the world. You see where borders and cities are, including national capitals. Imaginary, numbered lines- the equator and lines of latitude and longitude – give you the exact position on Earth of places they pass through. Some of the largest independent nations in the world are the Russian Federation, People’s Republic of China, the United States of America, Canada, Australia, India, Brazil, Saudi Arabia, and Argentina. While the smallest nations include Vatican City, Monaco, Andorra, and Singapore.

As represented on the world map, some countries like Brazil, Australia, the USA, and Indonesia have long coastlines, while others are completely landlocked like Bhutan, Switzerland, Mongolia, and Lesotho.

The world political map shows dependent territories such as Greenland and the Faroe Islands of Denmark, as well as the French Overseas Territories, which are geographically and culturally distinct, enjoying some degree of autonomy but are not independent states.

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This type of map shows where the streets and roads in a town or city are. It will also show bus stops, stations, schools, hospitals, parks, and other useful and important places. The maps are of different sizes, shapes, and scales. Small maps are used to show the overview of a region’s major roads or routes while large maps give greater details and cover a large area. Highway maps give the overview of major routes within a region. Street maps mainly cover areas within a city or metropolitan area. A collection of road maps bound together in a book is referred to as road atlas. Road maps often use thin lines to indicate minor roads and thicker or bolder colors to indicate major roads.

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This type of map shows you the natural features in an area. These include mountains, volcanoes, rivers, lakes, seas, oceans, and deserts. Different colours and symbols are used to represent these features.

Continents:

The physical land mass of the world, the planet Earth, is divided into seven continents of Africa, North America, South America, Europe, Australia, Asia and Antarctica (It being the only uninhabited continent) . Asia with 29% of the world land mass is the largest and Australia with 5.9% of landmass the smallest. Mount Everest is the highest point on earth and Dead Sea the lowest.

Deserts:

Deserts occupy about 33% of the world land mass. Deserts, places on earth which have very little rainfall, can be either hot or cold. The largest cold deserts are the polar deserts of Antarctica and Arctic Circle. The largest sub tropical or hot deserts are the Sahara and Arabian Desert. Gobi and Kalahari are other large deserts.

Mountain ranges:

Mountains cover 24% of the earth land mass and are spread over all the continents. Asia has the largest area covered with mountains and Africa the least- only 3%. Himalayas, the Earth’s youngest mountains are also the highest. These mountains are still growing. Mount Everest at 8848 meters is the highest peak and K2 at 8611 meters, the second highest. Alps are the mountain ranges in Europe and Rockies in North America.

Oceans:

Over two-third of the Earth’s surface is covered with water and more than 97% of this water is contained in the oceans. The Pacific Ocean is the largest and deepest ocean in the world. The other oceans are Atlantic, Indian, Pacific, Southern and Arctic.

Lakes:

The earth is dotted with lakes-bodies of fresh or salt water surrounded by a land mass. Northern hemisphere has the majority of fresh water lakes. Aral Sea, Dead Sea, and Great Salt Lake are salt water lakes. Caspian Sea, if considered as a lake is the largest. Other large lakes are Lake Michigan in North America, Lake Victoria in Africa, and Lake Eyre in Australia.

Rivers:

Rivers are watercourses flowing towards oceans, seas, lakes or another river. The Nile River, in Africa, with a length of 6695 kilometers is the longest in the world. The Brahmaputra and the Ganges are rivers in Asia. The Colorado and the Mississippi are rivers in North America. The Amazon, the second largest river, is in South America. River Congo, in Africa is the deepest river though it is the ninth longest.

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An urban area is the region surrounding a city. Most inhabitants of urban areas have non agricultural jobs. Urban areas are very developed, meaning there is a density of human structures such as houses, commercial buildings, roads, bridges, and railways.

“Urban area” can refer to towns, cities, and suburbs. An urban area includes the city itself, as well as the surrounding areas. Many urban areas are called metropolitan areas, or “greater,” as in Greater New York or Greater London.

When two or more metropolitan areas grow until they combine, the result may be known as a megalopolis. In the United States, the urban area of Boston, Massachusetts, eventually spread as far south as Washington, D.C., creating the megalopolis of BosWash, or the Northeast Corridor.

Settlements:

Settlement refers to the physical spaces and environments in which households are sheltered, and how one shelter relates to others. The term is generally used in the context of displaced populations to describe the temporary or sometimes permanent living arrangements of displaced families. In this context settlements can range from planned camps to dispersed accommodation in host villages/neighbourhoods, collective centres, spontaneous camps, rental accommodation, etc.

An urban settlement is where displaced populations settle within an urban agglomeration such as a town or city. A master plan usually divides towns or cities into zones regulated by norms based on specific sectors such as housing, hygiene, habitat, and environment. Zones are inclusive of residential areas, services and infrastructures, and spaces for administrative, commercial and industrial activities.

 Facilities:

Usually, there are lots of shops, schools, libraries, and hospitals. There may also be sports centres and swimming pools. The land uses and buildings that are used to serve the educational purposes of the community. These facilities very often have a secondary function of providing a location for social and recreational activities of the community. Health category of urban object includes all facilities where medical treatment of some form is offered. For example, it would include a local GP clinic or a city hospital. This category is, however, not limited to clinical or medical healthcare, it includes all object related to the diagnosis, treatment and rehabilitation of people with sickness or illness. Buildings and facilities relating to government departments or entities. This would include, for example administration office associated with a government department or agency, police and fire services stations, etc. For the purposes of Urban Securipedia, government assets do not extend to recreational services or utilities such as water/waste/energy infrastructure or facilities.

 Population:

In many countries, most of the populations now live in towns and cities. This is because there are plenty of jobs and houses there. In the mid 1800s, only 2% of the entire human population lived in urban areas. By the 1950’s, the percentage of the human population living in urban areas was up to around 29%, and by 2009, that number had reached 50%. This number is expected to increase rapidly and by 2050, it is predicted that over 70% of the human population will live in urban areas.

Transport:

 Most towns and cities have good transport links. These include roads for buses and cars, railways, and airports. Travel is necessary to engage in spatially dispersed activities such as work, shopping, visits to friends, etc. In economic terms, travel is an intermediate good, because demand for travel is derived from the demand for other spatially separated goods and services. Thus, one travels in order to engage in work or to do shopping or see a film. Apart from sightseeing and some types of holiday, rarely do people travel simply for the sheer pleasure of the trip.

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A rural area is an open swath of land that has few homes or other buildings, and not very many people. 

A rural areas population density is very low. Many people live in a city, or urban area. Their homes and businesses are located very close to one another. In a rural area, there are fewer people, and their homes and businesses are located far away from one another.

Agriculture is the primary industry in most rural areas. Most people live or work on farms or ranches. Hamlets, villages, towns, and other small settlements are in or surrounded by rural areas. 

Wildlife is more frequently found in rural areas than in cities because of the absence of people and buildings. In fact, rural areas are often called the country because residents can see and interact with the country’s native wildlife.

Throughout the world, more people live in rural areas than in urban areas. This has been changing rapidly, however. Urbanization is happening all over the world. In Asia, for example, the United Nations estimates that the urban population will increase by almost 2 billion by 2050. 

Open spaces:

These are common in rural areas. Some are conservation areas that are specially protected. The purpose of an open space reserve may include the preservation or conservation of a community or region’s rural natural or historic character; the conservation or preservation of a land or water area for the sake of recreational, ecological, environmental, aesthetic, or agricultural interests; or the management of a community or region’s growth in terms of development, industry, or natural resources extraction.

Facilities:

Rural areas often have few or no shops, hospitals, or post offices. Peoples may have to travel to the city to find them. People in rural areas generally have less access to healthcare than their urban counterparts. Fewer medical practitioners, mental health programs and healthcare facilities in these areas often mean less preventative care and longer response times in emergencies. The lack of healthcare workers has resulted in unconventional ways of delivering healthcare to rural dwellers, including medical consultations by phone or internet as well as mobile preventative care and treatment programs. There have been increased efforts to attract health professionals to isolated locations, such as increasing the number of medical students from rural areas and improving financial incentives for rural practices.

Settlements:

Settlement refers to the physical spaces and environments in which households are sheltered, and how one shelter relates to others. The term is generally used in the context of displaced populations to describe the temporary or sometimes permanent living arrangements of displaced families. In this context settlements can range from planned camps to dispersed accommodation in host villages/neighbourhoods, collective centres, and spontaneous camps, etc.

A rural settlement is where displaced populations settle on land outside of cities and towns. The population is often dependent on agricultural and pastoral practices, and has fewer community infrastructure systems than in urban settlements.

Agricultural:

A lot of the land in rural areas is used for growing crops and rearing animals for food. In rural areas throughout the world, agriculture represents the predominant land use and a major component of the viability of rural areas. Farming and related activities make up the basic fabric of rural life, contributing significantly to the overall state of rural regions in terms of employment and business opportunities, infrastructure and quality of the environment.

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Rocket and minerals make up much of our planet. They are formed deep inside the Earth over millions of Years. Rocks exist in lots of different shape, textures, and colours. They are mined to provide any of the things around us. Can you guess which rock is used where?

Granite:

Granite is and igneous rock which has extremely good weathering properties because it is very hard. This hardness makes it relatively difficult to work. Granite has been used in a large number of important buildings in the UK including Truro Cathedral, London Tower Bridge, Parts of St Pauls Cathedral, and Nelson’s Column. Granite has been mostly mined in the South West of England (Devon and Cornwall and in Aberdeenshire. Aberdeen is called the Granite City.

Iron ore:

Earth’s most important iron ore deposits are found in sedimentary rocks. They formed from chemical reactions that combined iron and oxygen in marine and fresh waters. The two most important minerals in these deposits are iron oxides: hematite (Fe2O3) and magnetite (Fe3O4). These iron ores have been mined to produce almost every iron and steel object that we use today – from paper clips to automobiles to the steel beams in skyscrapers.

Turquoise:

Turquoise is an opaque mineral that occurs in beautiful hues of blue, bluish green, green, and yellowish green. It has been treasured as a gemstone for thousands of years. Isolated from one another, the ancient people of Africa, Asia, South America and North America independently made turquoise one of their preferred materials for producing gemstones, inlay, and small sculptures.

 Rock salt:

Rock Salt is a chemical sedimentary rock that forms from the evaporation of ocean or saline lake waters. It is also known by the mineral name “halite”. It is rarely found at Earth’s surface, except in areas of very arid climate. It is often mined for use in the chemical industry or for use as a winter highway treatment. Some halite is processed for use as a seasoning for food. 

Marble:

Marble is a metamorphic rock that forms when limestone is subjected to the heat and pressure of metamorphism. It is composed primarily of the mineral calcite (CaCO3) and usually contains other minerals, such as clay minerals, micas, quartz, pyrite, iron oxides, and graphite. Under the conditions of metamorphism, the calcite in the limestone recrystallizes to form a rock that is a mass of interlocking calcite crystals. A related rock, dolomitic marble, is produced when dolostone is subjected to heat and pressure.

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There are three different groups of rock: igneous, sedimentary, and metamorphic. Rocks are classified into these three different groups, depending on how they were formed.

Igneous rock:

Igneous rocks (from the Greek word for fire) form from when hot, molten rock crystallizes and solidifies. The melt originates deep within the Earth near active plate boundaries or hot spots, then rises toward the surface. Igneous rocks are divided into two groups, intrusive or extrusive, depending upon where the molten rock solidifies.

Intrusive Igneous Rocks:
Intrusive, or plutonic, igneous rock forms when magma is trapped deep inside the Earth. Great globs of molten rock rise toward the surface. Some of the magma may feed volcanoes on the Earth’s surface, but most remains trapped below, where it cools very slowly over many thousands or millions of years until it solidifies. Slow cooling means the individual mineral grains have a very long time to grow, so they grow to a relatively large size. Intrusive rocks have a coarse grained texture.

Extrusive Igneous Rocks:
Extrusive, or volcanic, igneous rock is produced when magma exits and cools above (or very near) the Earth’s surface. These are the rocks that form at erupting volcanoes and oozing fissures. The magma, called lava when molten rock erupts on the surface, cools and solidifies almost instantly when it is exposed to the relatively cool temperature of the atmosphere. Quick cooling means that mineral crystals don’t have much time to grow, so these rocks have a very fine-grained or even glassy texture. Hot gas bubbles are often trapped in the quenched lava, forming a bubbly, vesicular texture.

Sedimentary rock:

Sedimentary rock is one of the three main rock groups (along with igneous and metamorphic rocks) and is formed in four main ways: by the deposition of the weathered remains of other rocks (known as ‘clastic’ sedimentary rocks); by the accumulation and the consolidation of sediments; by the deposition of the results of biogenic activity; and by precipitation from solution.

Sedimentary rocks include common types such as chalk, limestone, sandstone, clay and shale.

Sedimentary rocks cover 75% of the Earth’s surface.

Four basic processes are involved in the formation of a clastic sedimentary rock: weathering (erosion) caused mainly by friction of waves, transportation where the sediment is carried along by a current, deposition and compaction where the sediment is squashed together to form a rock of this kind.

Sedimentary rocks are formed from overburden pressure as particles of sediment are deposited out of air, ice, or water flows carrying the particles in suspension.

As sediment deposition builds up, the overburden (or ‘lithostatic’) pressure squeezes the sediment into layered solids in a process known as lithification (‘rock formation’) and the original connate fluids are expelled.

The term diagenesis is used to describe all the chemical, physical, and biological changes, including cementation, undergone by sediment after its initial deposition and during and after its lithification, exclusive of surface weathering.

Metamorphic rock:

Metamorphic rocks are rocks that have become changed by intense heat or pressure while forming. In the very hot and pressured conditions deep inside the Earth’s crust, both sedimentary and igneous rocks can be changed into metamorphic rock. In certain conditions these rocks cool and crystallize usually into bands of crystals. Later they can become exposed on Earth’s surface. One way to tell if a rock sample is metamorphic is to see if the crystals within it are arranged in bands.

One way to think about the metamorphic process (metamorphism) is to consider what happens when soft clay objects are put into a kiln and heated to a very high temperature. They change from being squashy to rock hard. They cannot be changed back to their original form. The material has been changed. This is what happens on a huge scale underground producing metamorphic rock.

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All of the land on Earth is divided up into seven large areas, called continents. These are North America, South America, Europe, Africa, Asia, Australia, and Antarctica. Each continent is divided u p again into a number of different countries.

North America:

This is the third largest continent, and has the fourth-largest population. North America runs from the America runs from the Arctic down to the equator, so the climate varies a lot.

North America occupies the northern portion of the landmass generally referred to as the New World, the Western Hemisphere, or simply the Americas. Mainland North America is shaped roughly like a triangle, with its base in the north and its apex in the south; associated with the continent is Greenland, the largest island in the world, and such offshore groups as the Arctic Archipelago, the West Indies, Haida Gwaii (formerly the Queen Charlotte Islands), and the Aleutian Islands.

South America:

South America, fourth largest of the world’s continents. It is the southern portion of the landmass generally referred to as the New World, the Western Hemisphere, or simply the Americas. The continent is compact and roughly triangular in shape, being broad in the north and tapering to a point—Cape Horn, Chile—in the south.

South America is bounded by the Caribbean Sea to the northwest and north, the Atlantic Ocean to the northeast, east, and southeast, and the Pacific Ocean to the west. In the northwest it is joined to North America by the Isthmus of Panama, a land bridge narrowing to about 50 miles (80 km) at one point. Drake Passage, south of Cape Horn, separates South America from Antarctica.

Antarctica:

Antarctica, fifth in size among the world’s continents. Its landmass is almost wholly covered by a vast ice sheet.

Lying almost concentrically around the South Pole, Antarctica—the name of which means “opposite to the Arctic”—is the southernmost continent, a circumstance that has had momentous consequences for all aspects of its character. It covers about 5.5 million square miles (14.2 million square km), and would be essentially circular except for the outflaring Antarctic Peninsula, which reaches toward the southern tip of South America (some 600 miles [970 km] away), and for two principal embayments, the Ross Sea and the Weddell Sea. These deep embayments of the southernmost Pacific and Atlantic oceans make the continent somewhat pear-shaped, dividing it into two unequal-sized parts. The larger is generally known as East Antarctica because most of it lies in east longitudes. The smaller, wholly in west longitudes, is generally called West Antarctica. East and West Antarctica are separated by the approximately 2,000-mile- (3,200-km-) long Transantarctic Mountains. Whereas East Antarctica consists largely of a high ice-covered plateau, West Antarctica consists of an archipelago of mountainous islands covered and bonded together by ice.

Europe:

Europe, second smallest of the world’s continents, composed of the westward-projecting peninsulas of Eurasia (the great landmass that it shares with Asia) and occupying nearly one-fifteenth of the world’s total land area. It is bordered on the north by the Arctic Ocean, on the west by the Atlantic Ocean, and on the south (west to east) by the Mediterranean Sea, the Black Sea, the Kuma-Manych Depression, and the Caspian Sea. The continent’s eastern boundary (north to south) runs along the Ural Mountains and then roughly southwest along the Emba (Zhem) River, terminating at the northern Caspian coast.

Europe’s largest islands and archipelagoes include Novaya Zemlya, Franz Josef Land, Svalbard, Iceland, the Faroe Islands, the British Isles, the Balearic Islands, Corsica, Sardinia, Sicily, Malta, Crete, and Cyprus. Its major peninsulas include Jutland and the Scandinavian, Iberian, Italian, and Balkan peninsulas. Indented by numerous bays, fjords, and seas, continental Europe’s highly irregular coastline is about 24,000 miles (38,000 km) long.

Africa:

Africa, the second largest continent (after Asia), covering about one-fifth of the total land surface of Earth. The continent is bounded on the west by the Atlantic Ocean, on the north by the Mediterranean Sea, on the east by the Red Sea and the Indian Ocean, and on the south by the mingling waters of the Atlantic and Indian oceans.

Africa’s total land area is approximately 11,724,000 square miles (30,365,000 square km), and the continent measures about 5,000 miles (8,000 km) from north to south and about 4,600 miles (7,400 km) from east to west. Its northern extremity is Al-Gh?r?n Point, near Al-Abya? Point (Cape Blanc), Tunisia; its southern extremity is Cape Agulhas, South Africa; its farthest point east is Xaafuun (Hafun) Point, near Cape Gwardafuy (Guardafui), Somalia; and its western extremity is Almadi Point (Pointe des Almadies), on Cape Verde (Cap Vert), Senegal. In the northeast, Africa was joined to Asia by the Sinai Peninsula until the construction of the Suez Canal. Paradoxically, the coastline of Africa—18,950 miles (30,500 km) in length—is shorter than that of Europe, because there are few inlets and few large bays or gulfs.

Australia:

Australia is a continent in the Southern Hemisphere, which comprises the countries of Australia, Tasmania, Seram, New Guinea, Timor, and other neighbouring islands. It is the smallest among the seven continents of the world, and lies on a continental shelf. Shallow seas divide the continent in to the different landmasses. The Torres Strait and Arafura Sea separate the mainland of Australia and New Guinea, and the Bass Strait lies between Tasmania and mainland Australia. They were actually connected by dry land in earlier times during the time around 18,000 BC, when the sea levels were lower. It was the Pleistocene ice age then. The sea levels have risen in the past ten thousand years, and that overflowed the lands and separated the different landmasses. New Zealand is not a part of the continent of Australia, but of the separate continent of Zealandia which is submerged. Both New Zealand and Australia are parts of the wider regions well known by Oceania or Australasia.

Asia:

Asia, the world’s largest and most diverse continent. It occupies the eastern four-fifths of the giant Eurasian landmass. Asia is more a geographic term than a homogeneous continent, and the use of the term to describe such a vast area always carries the potential of obscuring the enormous diversity among the regions it encompasses. Asia has both the highest and the lowest points on the surface of Earth, has the longest coastline of any continent, is subject overall to the world’s widest climatic extremes, and, consequently, produces the most varied forms of vegetation and animal life on Earth. In addition, the peoples of Asia have established the broadest variety of human adaptation found on any of the continents.Africa: This is the second-largest continent and has the most countries. The world’s longest river and the world’s largest desert are in Africa.

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Rocks go through many changes over time. These are caused by different processes, such as heating, cooling, and weathering. The sequence of changes is called the rock cycle.

Igneous rock:

Igneous rocks form by the cooling of magma (molten rock material beneath the surface) or lava (molten rock material extruded onto the surface). Magma which originates at depths as great as 200 kilometers below the surface consists primarily of elements found in silicate minerals along with gases, notably water vapor. Because the molten material is less dense than the surrounding solidified rock, it works its way toward the surface where it flows out onto the surface as lava.

Cooling:

What would you do to turn a melted chocolate bar back into a solid? You’d cool it by putting it into the refrigerator until it hardens.

Similarly, liquid magma also turns into a solid — a rock — when it is cooled. Any rock that forms from the cooling of magma is an igneous rock. Magma that cools quickly forms one kind of igneous rock, and magma that cools slowly forms another kind. 

When magma rises from deep within the earth and explodes out of a volcano, it is called lava, and it cools quickly on the surface. Rock formed in this way is called extrusive igneous rock. It is extruded, or pushed, out of the earth’s interior and cools outside of or very near the earth’s surface. 

What if the magma doesn’t erupt out of a volcano, but instead gets pushed slowly upward toward the earth’s surface over hundreds, thousands, or even millions of years? This magma will also cool, but at a much slower rate than lava erupting from a volcano. The kind of rock formed in this way is called intrusive igneous rock. It intrudes, or pushes, into the earth’s interior and cools beneath the surface. 

Melting:

What happens to a chocolate bar when it gets very hot? It melts.

The same thing happens to a rock when it is heated enough. Of course, it takes a lot of heat to melt a rock. The high temperatures required are generally found only deep within the earth. The rock is pulled down by movements in the earth’s crust and gets hotter and hotter as it goes deeper. It takes temperatures between 600 and 1,300 degrees Celsius (1,100 and 2,400 degrees Fahrenheit) to melt a rock, turning it into a substance called magma (molten rock). 

Metamorphic rock:

Metamorphic rocks are formed by the alteration of pre-existing rocks from exposure to heat and pressure while remaining in a solid form. Metamorphism occurs by breaking bonds between atoms in a mineral so that the atoms rearrange themselves into new, more stable, mineral forms. Rocks are transformed and remain in a solid state because not all the bonds in the rock’s minerals are broken – if they were the rock would melt.  Metamorphism occurs in solid rock because only some of the bonds between atoms are broken in an unstable mineral. As a result, the freed atoms and ions can migrate to another location within the mineral, or bond with atoms in a different mineral. The end result is to produce minerals that are more stable under the environmental conditions in which they exist. 

Metamorphism involves the transformation of a pre-existing rock to form new minerals and textures. The original mineral content of a rock can change in several ways. Unstable minerals like clay will breakdown and their elements will recombine to form new minerals. More stable minerals like quartz, will stay quartz but change shape and size to form a new configuration. At high temperatures, atoms and ions may move into a new orientation and bond into more stable forms. Hence, the type of minerals and its texture may change but the chemical composition of the rock itself can stay the same.

Uplift:

Understanding the idea of Uplift is the key to making sense of the rock cycle, as it allows us to see rocks that were once deeply buried beneath the surface.

If rocks did not get uplifted to form hills and mountains, then the processes of weathering and erosion would long ago have reduced much of the world’s land-masses to low-lying, flat plains. Weathering and erosion, transport and deposition would all effectively stop.

Scientists believe that, if all these active processes of the rock cycle ceased to operate, then our planet would cease to be able to support any life.

Mount Everest is made of limestone that must have originally formed on an ancient sea floor because it contains fossils of marine creatures.

Heat and Pressure:

The atoms in rocks rearrange to form bigger and heavier minerals. The combination of heat and pressure may cause the minerals in the rock to split into layers. Metamorphic rocks begin changing at temperatures of 100 degrees Celsius to 800 degrees Celsius. If you squeeze and heat a rock for a few million years, it can turn into a new kind of rock. 
The pressure comes from many layers of rock piling on top of each other, and the heat comes from magma.  It’s like putting blankets on yourself – the more you layers you put on, or the more blankets you put on, the more pressure you receive because of all the weight of the layers on top of you.

Sedimentary rock:

Sedimentary rocks are those formed from the compaction and cementation of fragments of pre-existing rocks called clasts, or plant and animals remains. The exogenic processes of weathering and erosion create the raw materials for sedimentary rocks. Earth material is loosened and moved from higher to lower elevations where it is deposited as transportation agents like water, wind or gravity lose their energy to move sediment. Streams and rivers transport sediment to lakes or oceans, or deposits it on nearby floodplains where it accumulates. On land, clastic sediments consist mainly of large boulders, cobbles, gravel, sand, and silt. On the continental shelves at the margin of continents, marine sediment is largely sand, silt, and clay. At the outer shelves and on the ocean floor, clays and chemically precipitated calcium carbonate and the remains of tiny marine animals accumulate.

Weathering and erosion:

Rocks are hard and strong, but they do not stay that way forever. Forces like wind and water break down rocks through the processes of weathering and erosion.

Weathering is the process that breaks down rocks. Many things cause weathering, including climate changes. Erosion breaks rocks down further and then moves them. Forces like wind and water move the rock pieces. They mix with matter like sand to become sediment. Weathering and erosion help shape Earth’s surface. They are part of a process called the rock cycle.

Transportation and deposition:

Eroded rock particles are carried away by wind or by rain, streams, rivers, and oceans. As rivers get deeper or flow into the ocean, their current slows down, and the rock particles (mixed with soil) sink and become a layer of sediment. Often the sediment builds up faster than it can be washed away, creating little islands and forcing the river to break up into many channels in a delta.

Sedimentation and cementation:

Cementation, in geology, hardening and welding of clastic sediments (those formed from preexisting rock fragments) by the precipitation of mineral matter in the pore spaces. It is the last stage in the formation of a sedimentary rock. The cement forms an integral and important part of the rock, and its precipitation affects the porosity and permeability of the rock. Many minerals may become cements; the most common is silica (generally quartz), but calcite and other carbonates also undergo the process, as well as iron oxides, barite, anhydrite, zeolites, and clay minerals.

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Soil is made up of broken rocks, minerals, decaying plants and animals, tiny creatures, gases, and water. If a section is cut through soil, you will see many layers. The depth of the layers vary in different soils.

Humus:

Humus, nonliving, finely divided organic matter in soil, derived from microbial decomposition of plant and animal substances. Humus, which ranges in colour from brown to black, consists of about 60 percent carbon, 6 percent nitrogen, and smaller amounts of phosphorus and sulfur. As humus decomposes, its components are changed into forms usable by plants.

Topsoil:

It is also called the humus layer, which is rich in organic material. This layer consists of decomposed material and organic matter. This is the reason; the topsoil has a dark brown color. The hummus makes the topsoil soft, porous to hold enough air and water. In this layer, the seeds germinate and roots of the plants grow. Many living organisms like earthworms, millipedes, and centipedes, bacteria, and fungi are found in this layer of soil.

Leaching layer:

Leaching, loss of soluble substances and colloids from the top layer of soil by percolating precipitation. The materials lost are carried downward (eluviated) and are generally redeposited (illuviated) in a lower layer. This transport results in a porous and open top layer and a dense, compact lower layer. The rate of leaching increases with the amount of rainfall, high temperatures, and the removal of protective vegetation. In areas of extensive leaching, many plant nutrients are lost, leaving quartz and hydroxides of iron, manganese, and aluminum. This remainder forms a distinctive type of soil, called laterite, or latosol, and may result in deposits of bauxite. In such areas rapid bacterial action results in the absence of humus in the soil, because fallen plant material is completely oxidized and the products are leached away. Accumulations of residual minerals and of those redeposited in lower layers may coalesce to form continuous, tough, impermeable layers called duricrusts.

Weathered rock:

Weathering is the name given to the process by which rocks are broken down to form soils. Rocks and geological sediments are the main parent materials of soils (the materials from which soils have formed). There is a very wide variety of rocks in the world, some acidic, some alkaline, some coarse-textured like sands, and some fine-textured and clayey. It is from the rocks and sediments that soils inherit their particular texture. When you see rocks in the landscape it is easy to appreciate how long the process of breaking down rocks to form soil takes. In fact, it can take over 500 years to form just one centimetre of soil from some of the harder rocks. Fortunately, in some respects at least, huge amounts of rocks were broken down during the Ice Age over 10,000 years ago and converted into clay, sands or gravels, from which state it was easier to form soils.

Subsoil:

It is comparatively harder and compact than topsoil. It is lighter in color than the topsoil because there is less humus in this layer. This layer is less organic but is rich in minerals brought down from the topsoil. It contains metal salts, especially iron oxide in a large proportion. 

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Soil is the layer of loose material between the surface and the solid rock below the ground.  Chances are that you haven’t thought a lot about the soil under your feet, but you may be surprised at the complexity of soil. Soil varies in its composition and the structure of its particles, and these factors are closely examined by farmers, who need appropriate soil for planting crops, as well as engineers who may need to understand how soil is going to hold up under different demands. Soil is also vitally important to the sustainability of an ecosystem because it serves as the natural medium for the growth of vegetation. Nothing can grow on Earth without it, but the soil varies in different places.

Grasses:

The soil is rich in nutrients, so many grasses can grow healthy and quickly.  They are an important source of food for man; they play an important ecological role in nature; and they are good protectors of the soil against soil erosion. The greatest value of grass is perhaps the role that grass plays in stabilizing and protecting the soil and for this reason the grass family is probably the most important plant family on earth.

Long roots:

Trees and grasses have long roots that go deep down to collect as much water as possible from the soil. Roots grow through the whole life of the plant. They grow longer from the tip, adding cells to the end of each root. The root adds cells to their tips, and they grow fatter as they add cells around their tube-like bodies.

At the tip of each root, there is a small group of tough, dead, hard cells called the root cap. The root cap is the strongest part of the root tip, and its job is to push its way through the dirt to look for moisture and nutrients and protect the plant.

Dung beetle:

These creatures feed on and break up, or decompose, animal poo, adding nutrients to the soil. Dung beetles aerate and mix the soil by burrowing, and increase the organic matter content of the soil by burying dung. These changes improve the water holding capacity and nutrient availability of the soil, with associated benefits to plants. By burying dung, they also provide an important food source for decomposers, and reduce resources for the larvae of economic insect pests such as bushflies

Leafcutter ants:

Ants dig tunnels into the soil, letting in air and moving around decaying plants and animals, which add nutrients to the soil. Leaf-cutting ants modify soil fertility through two mechanisms. First, the building, enlargement, and maintenance of nests ants affect soil structure, porosity and density. Second, leafcutters collect and concentrate vegetal material inside their nests to maintain their fungus culture, the food for most of the colony. As a result of this process, ants generate a huge quantity of organic waste that is deposited in nest cavities or dumps on the soil surface.

Buttress roots:

Trees have shallow roots underground to quickly take in the water and nutrients in the topsoil. Most rainforest soil is very poor with all the nutrients available largely remaining at surface level. Because of this rainforest trees have very shallow roots. 

Some very tall trees have developed ways of obtaining much needed additional support by forming buttressed roots, which grow out from the base of the trunk sometimes as high as 15 ft above the ground. These extended roots also increase the area over which nutrients can be absorbed from the soil.

Forest floor:

Many leaves from the thick tree canopy fall to the dark forest floor and decay. The major compartments for the storage of organic matter and nutrients within systems are the living vegetation, forest floor, and soil. The forest floor serves as a bridge between the above ground living vegetation and the soil, and it is a crucial component in nutrient transfer through the biogeochemical cycle. Much of the energy and carbon fixed by forests is periodically added to the forest floor through litterfall, and a substantial portion of the nutrient requirements of forest ecosystems is supplied by decomposition of organic matter in the forest floor and soil surface. 

Autumn leaves:

As the weather gets cooler and the days get shorter in the fall, trees start to prepare for winter. Trees use sunlight to make a special layer or seal between each leaf and the branch it is connected to. Then the leaves fall easily to the ground, leaving the branches of the tree protected from the cold that will come in the winter and also helping the tree store up food!

Since leaves have water inside their cells, they can’t survive freezing temperatures, because the water would freeze and the leaves would die. When leaves fall to the ground, they eventually break down and provide nutrients for the soil, helping prepare for more plants to grow in the spring and also create a layer that helps the ground absorb water.

Earthworm:

Earthworm burrows alter the physical structure of the soil. They open up small spaces, known as pores, within the soil. When earthworms are introduced to soils devoid of them, their burrowing can lead to increases in water infiltration rates of up to 10 times the original amount. This brings water and soluble nutrients down to plant roots. Burrowing also improves soil aeration (important for both plants and other organisms living in the soil) and enhances plant root penetration.

Tree roots:

Tree roots absorb nutrients and water from the soil. Large roots anchor the tree into the ground to prevent it from blowing over in the wind. Most roots live just 6-12 inches below ground and extend far beyond the width of the tree’s canopy. Cutting tree roots can cause stress to a tree and can leave it vulnerable to disease or insect attack. Roots need oxygen. By allowing soil to dry for several days between watering, oxygen can make its way to the roots. Avoid piling new soil or compacting the ground underneath the tree. This can suffocate the roots that absorb oxygen close to the surface. 

 Cactus:

Cacti have shallow roots and thick stems, so they can collect and store water. Cacti can have many small, thin roots near the top of the soil. These roots take in water quickly after a rain. The same cactus may have one long, thick root called a taproot. The taproot grows deep in the soil. It can reach water when the soil on top is dry.

Deep roots:

Desert trees have very long roots to reach down and collect water from deep underground. There are several benefits to a deep root system rather than a large surface root system. A deep root system helps the plants stay grounded in the soil through harsh winds and other adverse conditions. And the plant is not dependent on rainfall to get water for survival.

Kangaroo rat:

When burrowing, animals break down large rocks, mix up the soil, and let air into it. Kangaroo rats play an important in the ecological communities in which they live. Specifically, they influence plant growth by feeding on and dispersing seeds and digging burrows in the soil. This contributes to the overall health of their ecosystem. They are also prey for numerous predators, including barn owls, burrowing owls, snakes, and coyotes. In order to help keep ecosystems healthy, we have worked with our partners to translocate kangaroo rats out of areas that are slated for development and into appropriate habitat on protected reserves.

Grassland:

The soil is usually deep and full of nutrients. This is because rotting grass roots help to hold the soil together and add nutrients for new plants. Plants compete for water. Grasslands occur in environments conducive to the growth of this plant cover but not to that of taller plants, particularly trees and shrubs. The factors preventing establishment of such taller, woody vegetation are varied.

Tropical rainforest:

The soil is very wet and many plants grow, so there is lots of humus to add nutrients to the soil. However, these nutrients are washed away by the constant rain, leaving shallow, acidic soil. Most tropical rainforest soils relatively poor in nutrients. Millions of years of weathering and torrential rains have washed most of the nutrients out of the soil. More recent volcanic soils, however, can be very fertile. Tropical rain forest soils contain less organic matter than temperate forests and most of the available nutrients are found in the living plant and animal material. Nutrients in the soil are often in forms that are not accessible by plants.

Constant warmth and moisture promote rapid decay of organic matter. When a tree dies in the rainforest, living organisms quickly absorb the nutrients before they have a chance to be washed away. When tropical forests are cut and burned, heavy rains can quickly wash the released nutrients away, leaving the soil even more impoverished. 

Temperate deciduous forest:

The soil is moist and full of nutrients from decaying plants and animals, especially in autumn. The deep roots of plants break up the bedrock, which adds minerals. Water often drains through steadily.
The soil of deciduous forests is classified as an alfisol or a brown forest soil.  It is very nutrient rich. This is caused by the large leaf fall during the fall seasons.  When the snow melts in the spring the leaves on the ground decompose and supply the nutrients that the plants need to grow.  This type of soil was considered the most fertile type of soil until the modern inventions allowed other types of soil to be modified.

Desert:

The soil is very dry and few plants grow, so there is little humus. It is made up of boulders, pebbles, and sand, and is blown around by the wind. Any water drains through the sand easily. Deserts soils are generally of brown, light brown or reddish color. Due to arid conditions, leaching of soil is almost absent in the desert soils and thus evaporation is quite rapid.

Therefore, these soils are in general saline. Further in some low level areas, the salt content in the desert soil is really high. In fact, it is so high that common salt is obtained by evaporating the saline water collect from such areas.

However, salt content in some desert soils is not that high and thus in such cases they support vegetation in the sufficient availability of water. Moreover, in some areas land is rocky and is surrounded by gravel.

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Spectacular Angel Falls is the world’s tallest waterfall. With a drop of 979 m (3,212 ft), it is more than twice the height of New York’s Empire State Building. American pilot Jimmy Angel first spotted the waterfall from the air in 1933.

Lying within the Canaima National Park, Angel Falls is part of the plateau that underlies the lands located in Venezuela to the south of the Orinoco River. The plateau’s age is estimated at two billion years. Important geological transformations can be seen at the park, from its beginnings in the Precambrian period dating back to the time of the formation of the super continent Pangaea.

This continent began to separate due to the formation of a fracture in the planet’s crust resulting in the formation of the Atlantic Ocean, and the creation of different portions of lands called shields. The geographic region in Venezuela, known as the Guyanese Shield, existed from the start as a great plain at an elevation roughly as high as today’s visible tepuis, about 6500 to 9800 feet. After the formation of the great plain, during a long period of time—approximately 400 to 200 million years ago—a series of climate-related phenomena caused important changes in the geography of the Guyanese Shield.

The transformation of the landscape was due to drastic variations of arid climate to humid and vice versa; of strong, constant and lingering precipitations; droughts, freezing, discharges with high and low temperatures; storms, hurricanes, and the tectonic movements of the earth. The erosion was caused by atmospheric agents removing the material deposited in the great plain during millions of years. In places where the rock was less resistant, the erosion was greater resulting in this great transformation, the Tepuis, and the fantastic scenery at the Falls.

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Covering 1,000 km (600 miles), Atacama Desert, Chile South American desert is one of the driest places on Earth. Some parts have not seen rainfall since records began at least 400 years ago! The northern part of the Atacama Desert contained valuable minerals. Bolivia and Chile attempted to claim the area in the 1800s, causing the War of the Pacific from 1879 to 1884. Chile claimed victory and won control of the region. The extreme ecosystem of the Atacama makes survival difficult for animals. However, red scorpions, grey foxes, desert wasps and butterflies are among the species able to cope with the dry environment. You can also find penguins, sea lions and pelicans nearer the Pacific side.

The Atacama Desert was at the centre of the world’s attention in 2010. Famous for the ‘Copiapo mining accident’, whereby 33 miners survived a record 69 days buried in a 120-year-old copper-gold mine. Thankfully, all 33 miners were safely rescued on 13th October 2010. Often compared to the planet Mars, the Atacama’s landscape and soils are unique. Its appearance is unlike other deserts and several movies and television programmes have been filmed in the area. One of the most famous of which is A Space Odyssey. The Atacama Desert is one of the top three destinations for visitors to Chile. The other top attractions include Easter Island and Chile’s Lake District.

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Krubera Cave, Georgia is the world’s deepest cave lies in Asia, Stretching down 2,197 m (7,208 ft), it is nearly as deep as seven of Paris’s Eiffel Towers. Russians call the cave Voronya, meaning “crow’s cave”, after the many crows nesting at the entrance.

Krubera Cave is a deep, mostly vertical cave system. Passages in the cave system can be narrow and difficult to pass or wide and very large. In order to explore the caves completely cave divers need to be prepared to put on scuba gear because tunnels in the caves can sometimes become flooded. Flooded tunnels are referred to as sumps. Some of the passageways in Krubera Cave had to be widened to make it possible for cave divers and explorers to venture further.

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The world’s longest river is the Nile, at 6,825 km (4,238 miles) in length. It flows through 11 African countries, from Burundi to Egypt, where it meets the Mediterranean Sea. The Nile takes its name from the Greek for “river valley”.

The availability of water from the Nile throughout the year, combined with the area’s high temperatures, makes possible intensive cultivation along its banks. Even in some of the regions in which the average rainfall is sufficient for cultivation, marked annual variations in precipitation often make cultivation without irrigation risky.

The Nile River is also a vital waterway for transport, especially at times when motor transport is not feasible—e.g., during the flood season. Improvements in air, rail, and highway facilities beginning in the 20th century, however, greatly reduced dependency on the waterway.

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The peak of Mount Everest lies 8,848 m (29,029 ft) above sea level, making it the world’s highest mountain. It is ten times taller than the world’s tallest building- the Burj Khalifa skyscraper in Dubai.

Mount Everest attracts many climbers, some of them highly experienced mountaineers. There are two main climbing routes, one approaching the summit from the southeast in Nepal (known as the “standard route”) and the other from the north in Tibet. While not posing substantial technical climbing challenges on the standard route, Everest presents dangers such as altitude sickness, weather, and wind, as well as significant hazards from avalanches and the Khumbu Icefall. As of 2017, nearly 300 people have died on Everest, many of whose bodies remain on the mountain.

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If a stalagmite and stalactite become long enough and meet, they will form a rocky column. Columns are also created when a stalactite grows down to touch the cave floor.

As compound cave formations, they include among their ranks the tallest free-standing speleothems in the world. (Certain flowstone falls–sheets of calcite lining vertical shafts–are undoubtedly taller, but rarely measured). The towering specimens of the upper left photo, from Ogle Cave in Carlsbad Cavern National Park, New Mexico, USA, are indeed impressive. These, however, are only about half as high as the 61-meter tall column in Tham Sao Hin, a cave in Thailand.

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These thin, hollow tubes also form from dissolved particles in water, dripping slowly through the roof of a cave. They may grow into stalactites if the water keeps dripping for a very long time.

These tubes form when calcium carbonate or calcium sulfate dissolved in the water comes out of solution and is deposited. In soda straws, as each drop hovers at the tip, it deposits a ring of mineral at its edge. It then falls and a new drop takes its place. Each successive drop of water deposits a little more mineral before falling, and eventually a tube is built up. Stalagmites or flowstone may form where the water drops hit the cave floor.

Soda straws are some of the most fragile of speleothems. Like helictites, they can be easily crushed or broken by the slightest touch. Because of this, soda straws are rarely seen within arms’ reach in show caves or others with unrestricted access. Kartchner Caverns in southern Arizona has well-preserved soda straws because of its recent discovery in 1974 and highly regulated traffic.

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These hang down like icicles. They form in the same way as stalagmites, from rocky particles dissolved in water, this time dripping from the caves ceiling.

A drop on the tip of a growing stalactite leaves a deposit only around its rim. Downward growth of the rim makes the tube. The simplest stalactite form, therefore, is a thin-walled stone straw, and these fragile forms may reach lengths of 0.5 m (20 inches) or more where air currents have not seriously disturbed the growth. The more common form is a downward-tapering cone and is simply a thickening of the straw type by mineral deposition from a film of water descending the exterior of the pendant.

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Water dripping onto the cave floor leaves behind tiny rocky particles that were dissolved in it. As the dripping continues, these particles can build up form a pillar of rock, or stalagmite.

Stalagmites have thicker proportions and grow up on the bottom of a cavern from the same drip-water source, the mineral from which is deposited after the water droplet falls across the open space in the rock. Not every stalactite has a complementary stalagmite, and many of the latter may have no stalactite above them. Where the paired relation exists, however, continual elongation of one or both may eventually result in a junction and the formation of a column.

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Caves are underground spaces or hole that are large enough for someone to enter. They form in many different ways, but mostly because of rock in the Earth’s surface being worn away or crumbling. Caves usually have lots of interesting and exciting features to explore.

There are many types of caves formed through different processes: some are small, and it is difficult for man to penetrate into; others, on the contrary, stretch underground for tens or hundreds of kilometres, reaching depths of over 2,000 m. Formation processes control length, development and shape of a cave, and also the difficulties that will arise when exploring them. Most of the longest and deepest caves do not consist in an isolated cavity, but they form a system, which at times may be very complex, made of rooms, sinkholes, shafts, meanders, canyons, interconnecting galleries, which are arranged to form a system or karst complex.
Large quantities of underground water move through karst systems, caves may therefore be classified in different sub-areas, i.e. occupied by air and completely dry or scoured by streams, they may be flooded at times, or permanently invaded by fresh and salt water.

Caves are found all over our planet. Some are small, single spaces, but others contain many chambers, linked by tunnels to form a huge maze of different areas. Although most caves are found in rock, some form in ice or lava.

Solutional caves

These are the most common type of cave. They are created when a build up acidic water dissolves the rock around it. Holes and tunnels start to appear, getting bigger and bigger as more rock dissolves and is washed away.

Solution caves are formed when groundwater seeps underground via cracks, faults, joints, bedding places, and other surface openings. Over geological epochs, small cracks in the rock become large cave systems. Limestone solution caves are very picturesque as they are often adorned with cave formations like stalactites and stalagmites formed by calcium carbonate precipitation. Such caves are formed by the dissolution of limestone by acidic water (water with dissolved carbonic acid).

Lava caves

When lava flows slowly over land around a volcano, it can harden on the surface, leaving liquid lava flowing underneath. This liquid drains away, leaving a hollow tube of rock that forms a cave.

When hot liquid lava flows down the slope of a volcano, the surface of the lava cools and solidifies. However, hot liquid lava continues to flow beneath the solidified surface and when the flow stops, a hollow tube remains. Such types of caves are called lava tubes. Lava mold caves, rift caves, inflationary caves, and volcanic conduits are other caves formed by volcanic activity. The Kazumura Cave in Hawaii is an example of a 65.8 km long lava tube.

Ice caves

Ice melting on top of a glacier can form a stream or waterfall that flows through the glacier. Eventually, this flowing water will hollow out part of the glacier, creating an ice cave.

The second type of ice cave occurs either when frigid winter air settles into downward-leading caverns where it cannot be forced out or when moisture freezes in currents of cold air. Frozen lakes, icicles, and ice draperies are common formations. Helictite-like icicles also form where air currents deflect the freezing water. The splendid ice deposits formed in the lava caves of the northwestern United States are dwarfed by the limestone ice-cave systems of the Alps.

Sea Caves

These are formed by waves constantly battering against cliffs along the seashore. This leads to cracks appearing in the cliffs that get larger as beating waves continue to wear away the rock.

Sea caves are often a major tourist attraction. Some sea caves can be accessed only by boats during low tide while others are more easily accessible and occur along beaches where it is possible to walk into the caves. Cathedral Cove Sea Cave, in Coromandel, New Zealand is an example of a sea cave.

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This is where a river starts, high up in the mountains. The source, or place where the river starts from, could be a springs or a lake, or even a melting glacier. A river can have more than one source.

The source is the farthest point of the river stream from its estuary or its confluence with another river or stream. Rivers are usually fed by many tributaries. The farthest stream is called the head-stream or head water. There is sometimes disagreement on which source is the head water, hence on which is the true source. Headwaters are usually in mountains. Glacial headwaters are made by melting glaciers.

The source is where a river begins, and the mouth is where it joins the sea. The source of a river generally discharges water with less force leading to the formation of Interlocking spurs.

The river mouth is the opposite of a river source. The mouth is where the river ends as it meets the ocean, and may have a river delta.

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A river is a natural channel of fresh water that flows across the Earth’s surface. All rivers start in mountains or hills and flow down towards the sea or ocean, or into another large area of water. They may be short or flow for hundreds of kilometres.

Rivers are part of the hydrological cycle; water generally collects in a river from precipitation through a drainage basin from surface runoff and other sources such as groundwater recharge, springs, and the release of stored water in natural ice and snowpacks (e.g., from glaciers). Potamology is the scientific study of rivers, while limnology is the study of inland waters in general. Most of the major cities of the world are situated on the banks of rivers, as they are, or were, used as a source of water, for obtaining food, for transport, as borders, as a defensive measure, as a source of hydropower to drive machinery, for bathing, and as a means of disposing of waste.

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Weathering occurs when rocks are weakened, so that they crack and then break up into smaller pieces. This natural process can be caused by rainfall, changes in temperature or even by plants as they grow. Weathering and erosion constantly change the rocky landscape of Earth. Weathering wears away exposed surfaces over time. The length of exposure often contributes to how vulnerable a rock is to weathering. Rocks, such as lavas, that are quickly buried beneath other rocks are less vulnerable to weathering and erosion than rocks that are exposed to agents such as wind and water.

As it smoothes rough, sharp rock surfaces, weathering is often the first step in the production of soils. Tiny bits of weathered minerals mix with plants, animal remains, fungi, bacteria, and other organisms. A single type of weathered rock often produces infertile soil, while weathered materials from a collection of rocks is richer in mineral diversity and contributes to more fertile soil. Soils types associated with a mixture of weathered rock include glacial till, loess, and alluvial sediments.

Biological Weathering:

This is when plants or animals cause rocks to break up. Plant rocks to break up. Plant roots often grow into small cracks in rocks, splitting them apart. An animal digging can also turn rocks into rubble.

Microscopic organisms like algae, moss, lichens and bacteria can grow on the surface of the rocks and produce chemicals that have the potential of breaking down the outer layer of the rock. They eat away the surface of the rocks. These microscopic organisms also bring about moist chemical micro-environments which encourage the chemical and physical breakdown of the rock surfaces. The amount of biological activity depends upon how much life is in that area. Burrowing animals such as moles, squirrels and rabbits can speed up the development of fissures.

Chemical Weathering: 

Chemical reactions can break up rock. Acid rain, for example, destroys the stone in statues and buildings.

The natural chemical reactions within the rocks change the composition of the rocks over time. Because the chemical processes are gradual and ongoing, the mineralogy of rocks changes over time thus making them wear away, dissolve, and disintegrate.

The chemical transformations occur when water and oxygen interacts with minerals within the rocks to create different chemical reactions and compounds through processes such as hydrolysis and oxidation. As a result, in the process of new material formations, pores and fissures are created in the rocks thus enhancing the disintegration forces.

Physical or Mechanical Weathering: 

Wind water and temperature changes weaken rock. If water in a crack freezes, it expands and can tear a rock apart. One of the most common mechanical actions is frost shattering. It happens when water enters the pores and cracks of rocks, then freezes. Frost weathering, frost wedging, ice wedging or cryofracturing is the collective name for several processes where ice is present. These processes include frost shattering, frost-wedging and freeze-thaw weathering.

Another type of mechanical weathering is called salt wedging. Winds, water waves, and rain also have an effect on rocks as they are physical forces that wear away rock particles, particularly over long periods of time. These forces are equally categorized under mechanical or physical weathering because they release their pressures on the rocks directly and indirectly which causes the rocks to fracture and disintegrate.

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Erosion is the wearing away of rocks and other matter on the Earth’s surface by a natural force, such as a sliding glaciers, a flowing river, or the wind. Material that is rubbed off is carried away and deposited somewhere else.

Most erosion is performed by liquid water, wind, or ice (usually in the form of a glacier). If the wind is dusty, or water or glacial ice is muddy, erosion is taking place. The brown color indicates that bits of rock and soil are suspended in the fluid (air or water) and being transported from one place to another. This transported material is called sediment.

Water erosion

This is caused by falling rain or flowing water. Rivers, for example, wear away the land that they flow over, changing the surrounding landscape. Raindrops hit bare soil with enough force to break the soil aggregates. These fragments wash into soil pores and prevent water from infiltrating the soil. Water then accumulates on the surface and increases runoff which takes soil with it.

Well-structured soils are less prone to break up, and the impact of raindrops is minimized if the soil surface is protected by plant or litter cover. 

Wind erosion

The force of the wind can remove pieces of rock and carry them off. Wind erosion is common in deserts. Wind erosion is a serious environmental problem attracting the attention of many across the globe. It is a common phenomenon occurring mostly in flat, bare areas; dry, sandy soils; or anywhere the soil is loose, dry, and finely granulated. Wind erosion damages land and natural vegetation by removing soil from one place and depositing it in another. It causes soil loss, dryness and deterioration of soil structure, nutrient and productivity losses and air pollution. Suspended dust and dirt is inevitably deposited over everything. It blows on and inside homes, covers roads and highways, and smothers crops. Sediment transport and deposition are significant factors in the geological changes which occur on the land around us and over long periods of time are important in the soil formation process.

Ice erosion

As glaciers move, they rub away the land under them, carrying the broken-down material with them. Ice erosion occurs in one of two forms, the movement of glaciers, or thawing processes. In the latter formation, water inside pores and rock fractures expand, which causes further cracking. Glaciers erode through one of three different processes, including abrasion, plucking, and thrusting. Debris caught in the basal brushes along the bed, which polishes and gouges the rocks underneath. Glaciers also cause bedrock to fall off during the plucking phase. In addition, glaciers freeze and then move forward, which dislodges the sediments at the glacier’s base. The latter method produces thousands of lake basins that lie across the edge of the Canadian Shield. All of these combined processes form moraines, drumlins, kames, moulins, and glacial erratics, especially at the glacier retreat.

Extreme cold weather temperatures cause trapped water particles to expand in its cracks, which breaks the rock into several pieces. This senior care leads to gravity erosion, particularly on steep slopes, and the formation of scree at the bottom of a mountainside. Morning thaws can present structural problems for roads alongside mountain cliffs. Additionally, trapped water in the wedge of a rock causes fissures, which eventually breaks down the rock.

Coastal erosion

Crashing waves gradually wear away the rock in cliffs, and sweep up material from the beach. Coastal erosion is typically driven by the action of waves and currents, but also by mass wasting processes on slopes, and subsidence (particularly on muddy coasts). Significant episodes of coastal erosion are often associated with extreme weather events (coastal storms, surge and flooding) but also from tsunami, both because the waves and currents tend to have greater intensity and because the associated storm surge or tsunami inundation can allow waves and currents to attack landforms which are normally out of their reach. On coastal headlands, such processes can lead to undercutting of cliffs and steep slopes and contribute to mass wasting. In addition, heavy rainfall can enhance the saturation of soils, with high saturation leading to a reduction in the soil’s shear strength, and a corresponding increase in the chance of slope failure (landslides).

Coastal erosion is a natural process which occurs whenever the transport of material away from the shoreline is not balanced by new material being deposited onto the shoreline. Many coastal landforms naturally undergo quasi-periodic cycles of erosion and accretion on time-scales of days to years. This is especially evident on sandy landforms such as beaches, dunes, and intermittently closed and open lagoon entrances. However, human activities can also strongly influence the propensity of landforms to erode.

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The glacier terminus is the lower end of a glacier. it is sometimes called the toe or snout. Some glaciers end further down a mountain, where the ice melts to form lakes and streams. Others reach the coast, where large chunks break off into the sea, creating icebergs. This is called calving.

Tracking the change in location of a glacier terminus is a method of monitoring a glacier’s movement. The end of the glacier terminus is measured from a fixed position in neighboring bedrock periodically over time. The difference in location of a glacier terminus as measured from this fixed position at different time intervals provides a record of the glacier’s change. A similar way of tracking glacier change is comparing photographs of the glacier’s position at different times.

The form of a glacier terminus is determined by many factors. If the glacier is retreating, it is usually mildly sloping in form because a melting glacier tends to assume this shape. But there are many conditions that alter this typical shape, including the presence of thermal fields and various stresses that cause cracking and melting feedback resulting in glacial calving and other diverse forms.

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Cirques 

Cirques are deep hollows near the top of a glacier, formed where a glacier has moved over an area and worn away the rock. The glacial cirque is opened on the downhill side while the cupped section is steep. The cliffs on the sides slope down and combine and converge from three or more higher sides. The floor of the cirque is bowl-shaped because of the convergence zones of combining ice flows from a different direction and the debris accompanying them. A Cirque experiences greater erosion because of the accompanying rock burdens which may also over deepen the level of a cirque. Cirques subjected to seasonal melting often form small lakes called tarns behind the Moraine.

Accumulation zones 

Accumulation Zones are found at the top of glaciers, where the snowfall has built up, often over hundreds of years. Glaciologists subdivide glaciers into glacier accumulation zones, based on the melting and refreezing occurring. These zones include the dry snow zone, in which the ice entirely retains subfreezing temperatures and no melting occurs. Dry snow zones only occur within the interior regions of the Greenland and Antarctica ice sheets. Below the dry snow zone is the percolation zone, where some melt water penetrates down into the glacier where it refreezes. In the wet snow zone, all the seasonal snow melts. The melt water either percolates into the depths of the glacier or flows down-glacier where it might refreeze as superimposed ice. A glacier’s equilibrium line is located at the lower limit of the wet snow zone.

Valley glaciers 

Valley glaciers flow through steep-walled valleys. They eventually wear down the valley sides, making them much rounder. Valley glaciers that flow far enough to reach the sea are called tidewater glaciers. Such glaciers are often the source of numerous small icebergs that might pose a problem to navigating vehicles. Often fjords are formed at the edges of such glaciers when the glaciers retreat and sea water fills the void. A hanging glacier is a part of a valley glacier system. Such glaciers originate high on a glacial valley’s walls and descend to a certain extent along the valley before making an abrupt stop, usually at a cliff. Such glaciers are called hanging glaciers and ice fall and avalanches originating at such glaciers are responsible for snow and ice on the valley floor lying below. When such hanging glaciers retreat, hanging valleys are formed. The Mer de Glace glacier on the Mont Blanc massif’s northern slopes is a valley glacier in the French Alps.

Lateral moraines 

Lateral moraines are long ridges of rock, soil, and dirt left along the sides of a moving glacier. They form only in the ablation zone of a glacier (where more ice is melting than is accumulating as snow each year). This makes them good indicators of where the line between the accumulation zone and the ablation zone—the equilibrium line—occurred on past glaciers. They often remain on the landscape long after glacier retreat and are frequently contiguous with terminal moraines.

Medical moraines 

A medial moraine is found on top of and inside an existing glacier. Medial moraines are formed when two glaciers meet. Two lateral moraines from the different glaciers are pushed together. This material forms one line of rocks and dirt in the middle of the new, bigger glacier. 

If a glacier melts, the medial moraine it leaves behind will be a long ridge of earth in the middle of a valley.

A glacier is a huge river of ice that forms when thick layers of snow fall on top of each other and are pressed together. Most glaciers form high up in mountains, where it’s so cold that any snowfall never melts. They are found all around the world, usually in polar and mountainous regions.

Most of the world’s glacial ice is found in Antarctica and Greenland, but glaciers are found on nearly every continent, even Africa. Because certain climatic and geographic conditions must be present for glaciers to exist, they are most commonly found above snow line: regions of high snowfall in winter and cool temperatures in summer. This condition allows more snow to accumulate on the glacier in the winter than will melt from it in the summer. This is why most glaciers are found either in mountainous areas or the Polar Regions. However, snow line occurs at different altitudes: in Washington State the snow line is around 1,600 meters (5,500 feet), while in Africa it is over 5,100 meters (16,732 feet), and in Antarctica it is at sea level. The amount of snowfall a glacier receives is very important to its survival, which is why some cold regions, like Siberia, have almost no glaciation—there is not enough snowfall.

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Near the sea, salt water mixes with fresh water, forming an estuary. The land is flatter, so the river slows down. If it slows down enough, mud is deposited, creating a delta with several channels that the river now flows through.

The basic difference between estuary and delta is that the former is a tidal mouth of the river, where it meets the sea, whereas the latter is nothing but the wetland, formed as a result of the accumulation of sediments carried by the river when it joins a standing water body.

While an estuary is a semi-enclosed body of water, where river meets the ocean, the delta is a low-lying plain, formed by the accumulation of alluvium. There is four major types of estuaries which are drowned river valley estuary, bar-built estuary, fjord estuary and tectonic estuary. On the contrary, various types of delta include wave-dominated delta, tide-dominated delta, Gilbert delta, tidal-freshwater delta, inland delta and mega-delta.

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These are flat areas of land next to a river. Water in river may increase for some reason and become too much for the river to carry. It then overflows onto the floodplain. Soil in floodplains is usually very fertile.

A flood plain consists of two parts. The first is the main channel of the river itself, called the floodway. Floodways can sometimes be seasonal, meaning the channel is dry for part of the year. 

Beyond the floodway is the flood fringe. The flood fringe extends from the outer banks of the floodway to the bluff lines of a river valley. Bluff lines, also called valley walls, mark the area where the valley floor begins to rise into bluffs.

Some rivers have very narrow flood plains. In fact, some rivers, or parts of rivers, seem to have no flood plain at all. These rivers usually have a steep stream gradient—a very deep, fast-moving channel. 

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A meander is a curve or bend in a river. It forms when the flow of water wears away the land on one side of the river, then dumps the broken-down rocks this creates on the other side, increasing the area of land there.

A meander is produced by a stream or river as it erodes the sediments comprising an outer, concave bank (cut bank) and deposits this and other sediment downstream on an inner, convex bank which is typically a point bar. The result of sediments being eroded from the outside concave bank and their deposition on an inside convex bank is the formation of a sinuous course as a channel migrates back and forth across the down-valley axis of a floodplain. The zone within which a meandering stream shifts its channel across either its floodplain or valley floor from time to time is known as a meander belt. It typically ranges from 15 to 18 times the width of the channel. Over time, meanders migrate downstream, sometimes in such a short time as to create civil engineering problems for local municipalities attempting to maintain stable roads and bridges.

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Rivers usually flow over a mixture of hard and soft rock. The force of the water will wear away more soft rock than harder rock. This happens both laterally (as a stream flows across the earth) and vertically (as the stream drops in a waterfall). In both cases, the soft rock erodes, leaving a hard ledge over which the stream falls.

A fall line is the imaginary line along which parallel rivers plunge as they flow from uplands to lowlands. Many waterfalls in an area help geologists and hydrologists determine a region’s fall line and underlying rock structure.

As a stream flows, it carries sediment. The sediment can be microscopic silt, pebbles, or even boulders. Sediment can erode stream beds made of soft rock, such as sandstone or limestone. Eventually, the stream’s channel cuts so deep into the stream bed that only a harder rock, such as granite, remains. Waterfalls develop as these granite formations form cliffs and ledges.

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Near its source, a river flows very fast. The rushing water wears away the surrounding rock. This widens and deepens the river channel, forming a gorge or V-shaped valley.

A V-shaped valley is formed when a flowing river cuts into the earth. The valley gets its V shape when rain and runoff flow down the banks of the river, causing erosion; V-shaped valleys are most commonly found in the mountains. The V-shaped valley gets its name because when looked at from the front, it looks like the letter V.

Yosemite Valley is one of the most popular V-shaped Valleys. It is located in the Yosemite National Park in California.

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A stream or river that flows into a larger river, rather than directly to the sea, is called a tributary. Some large rivers have hundreds of tributaries!

The larger, or parent, river is called the mainstem. The point where a tributary meets the mainstem is called the confluence. Tributaries, also called affluents, do not flow directly into the ocean.

Most large rivers are formed from many tributaries. Each tributary drains a different watershed, carrying runoff and snow melt from that area. Each tributary’s watershed makes up the larger watershed of the mainstem. 

Sometimes, tributaries have the same name as the river into which they drain. These tributaries are called forks. Different forks are usually identified by the direction in which they flow into the mainstem.

The opposite of a tributary is a distributary. A distributary is a stream that branches off and flows apart from the mainstem of a stream or river. The process is called river bifurcation. 

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When sea water filters down cracks in the Earth’s crust, it is heated by volcanic activity. Hot water then spurts out through the cracks or vents.

Hydrothermal vents exist because the earth is both geologically active and has large amounts of water on its surface and within its crust. Under the sea, hydrothermal vents may form features called black smokers or white smokers. Relative to the majority of the deep sea, the areas around submarine hydrothermal vents are biologically more productive, often hosting complex communities fueled by the chemicals dissolved in the vent fluids. Chemosynthetic bacteria and archaea form the base of the food chain, supporting diverse organisms, including giant tube worms, clams, limpets and shrimp. Active hydrothermal vents are believed to exist on Jupiter’s moon Europa, and Saturn’s moon Enceladus, and it is speculated that ancient hydrothermal vents once existed on Mars.

Hydrothermal vents in the deep ocean typically form along the mid-ocean ridges, such as the East Pacific Rise and the Mid-Atlantic Ridge. These are locations where two tectonic plates are diverging and new crust is being formed.

The water that issues from seafloor hydrothermal vents consists mostly of sea water drawn into the hydrothermal system close to the volcanic edifice through faults and porous sediments or volcanic strata, plus some magmatic water released by the upwelling magma. In terrestrial hydrothermal systems, the majority of water circulated within the fumarole and geyser systems is meteoric water plus ground water that has percolated down into the thermal system from the surface, but it also commonly contains some portion of metamorphic water, magmatic water, and sedimentary formational brine that is released by the magma. The proportion of each varies from location to location.

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A mid-ocean ridge or mid-oceanic ridge is an underwater mountain range, formed by plate tectonics.

This uplifting of the ocean floor occurs when convection currents rise in the mantle beneath the oceanic crust and create magma where two tectonic plates meet at a divergent boundary.

The mid-ocean ridges of the world are connected and form a single global mid-oceanic ridge system that is part of every ocean, making the mid-oceanic ridge system the longest mountain range in the world, with a total length of about 60,000 km.

There are two processes, ridge-push and slab-pull, thought to be responsible for the spreading seen at mid-ocean ridges, and there is some uncertainty as to which is dominant.

Ridge-push occurs when the weight of the ridge pushes the rest of the tectonic plate away from the ridge, often towards a subduction zone.

At the subduction zone, “slab-pull” comes into effect.

This is simply the weight of the tectonic plate being subducted (pulled) below the overlying plate dragging the rest of the plate along behind it.

The other process proposed to contribute to the formation of new oceanic crust at mid-ocean ridges is the “mantle conveyor”.

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When the tide goes out on rocky seashore, pools of water are left behind in holes in the rocks. These then become home to a huge range of plants and animals, such as shellfish and sea anemones.

As the tide recedes, not the entire coast is left behind dry. Depending on the type of rock, one can find shallow or deep rock pools. They offer better survival chances for animals and plants that need to be submerged all the time. Because each rock pool is different, they invite different communities. Deep rock pools near the low tide, have few survival problems, whereas shallow rock pools near the high tide, have many. Thus the pool’s placing on the shore as well as its depth and size are important factors.

Deep rock pools provide shelter from waves, allowing fragile organisms to live on an otherwise exposed rocky shore. Fragile animals are: sea slugs, shrimps, camouflage crabs, sea eggs, and small fishes. Fragile sea weeds are: Neptune’s necklace, pillow weed, cystophora, sea lettuce and many others.

For the snails that are able to survive in between high and low tide (periwinkle, nerita, melagraphia, cats eye) a rock pool is not necessarily a better place because their predators are found there (dark rock shell, white rock shell, trumpet shell). Large fish and octopus may find the rock pools too small, lacking oxygen for breathing. Rock pools may collect fresh water during rain storms, which is worse for shallow rock pools high up the shore where organisms must wait longer for the tide to return.

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These are made from the skeletons left by tiny sea animals, called coral polyps, when they die. The skeletons build up into huge reefs, where plants and other sea creatures live. The coral species that build reefs are known as hermatypic, or “hard,” corals because they extract calcium carbonate from seawater to create a hard, durable exoskeleton that protects their soft, sac-like bodies. Other species of corals that are not involved in reef building are known as “soft” corals.

Each individual coral is referred to as a polyp. Coral polyps live on the calcium carbonate exoskeletons of their ancestors, adding their own exoskeleton to the existing coral structure. As the centuries pass, the coral reef gradually grows one tiny exoskeleton at a time, until they become massive features of the marine environment.

Corals are found all over the world’s oceans, from the Aleutian Islands off the coast of Alaska to the warm tropical waters of the Caribbean Sea. The biggest coral reefs are found in the clear, shallow waters of the tropics and subtropics. The largest of these coral reef systems, the Great Barrier Reef in Australia, is more than 1,500 miles long (2,400 kilometers).

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When tectonic plates in the ocean floor move and collide, one may be pushed under the other, creating a narrow trench. These trenches are the deepest places in the Earth’s oceans.

Trenches are formed by subduction, a geophysical process in which two or more of Earth’s tectonic plates converge and the older, denser plate is pushed beneath the lighter plate and deep into the mantle, causing the seafloor and outermost crust (the lithosphere) to bend and form a steep, V-shaped depression. This process makes trenches dynamic geological features—they account for a significant part of Earth’s seismic activity—and are frequently the site of large earthquakes, including some of the largest earthquakes on record. Subduction also generates an upwelling of molten crust that forms mountain ridges and volcanic islands parallel to the trench. Examples of these volcanic “arcs” can be seen in the Japanese Archipelago, the Aleutian Islands, and many other locations around this area called the Pacific “Ring of Fire.”

Many of the organisms living in trenches have evolved surprising ways to survive in these unique environments. Recent discoveries in the hadal zone have revealed organisms with proteins and biomolecules suited to resisting the crushing hydrostatic pressure and others able to harness energy from the chemicals that leak out of hydrocarbon seeps and mud volcanoes on the seafloor. Other hadal species thrive on the organic material that that drifts down from the sea surface and is funneled to the axis of the V-shaped trenches.

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This is the top layer of the ocean, nearest the surface. The open ocean is vast. Although food can sometimes be hard to find, many animals, such as dolphins, seals, and turtles, live there.

Many open ocean organisms live out their existence without ever coming into contact with the shore, the seafloor, or the water’s surface. They spend their entire lives surrounded by water on all sides and do not know that anything else even exists. In the case of the deep open ocean, organisms never even see sunlight. As land mammals that breathe air, walk on land, and rely on our sense of sight for almost all functions, it is difficult for people (even experts) to comprehend that most of the organisms on the planet are never exposed to air, land, or sunlight.

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These islands are formed from layers of magma, or liquid rock, which erupts from a volcano under the water, then cools and hardens. The magma layers eventually build up to create an island.

Volcanic islands are formed by volcanic activity on the seabed, often near the boundaries of the tectonic plates that form Earth’s crust. Where two plates pull apart, lava erupts to form an undersea ridge. Layers of lava build up until a ridge breaks the sea’s surface to form an island. Sometimes a whole chain of volcanic islands, called an island arc, is formed in this way. Some island arcs contain thousands of islands.

Sometimes, volcanoes occur in close proximity to each other on the sea floor, creating a very large island. For example, the big island of Hawaii is actually five, side-by-side volcanoes that have grown together. The island chain of countries that make up Southeast Asia; Indonesia and Papua New Guinea, the Philippine Islands were all created by volcanic activity on the sea floor. New Zealand, the Island country off the Southeast coast of Australia, was also formed by ancient volcanoes.

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Around 71 percent of the Earth’s surface is covered by oceans. Many different and interesting features are found in and around them, and a huge variety of animals and plants have adapted to life in this watery world. Humans depend on these teeming waters for comfort and survival, but global warming and overfishing threaten to leave the ocean agitated and empty.

The oceans hold about 320 million cubic miles (1.35 billion cubic kilometers) of water, which is roughly 97 percent of Earth’s water supply. The water is about 3.5 percent salts and contains traces of all chemical elements found on Earth. The oceans absorb the sun’s heat, transferring it to the atmosphere and distributing it around the world via the ever-moving ocean currents. This drives global weather patterns and acts as a heater in the winter and an air conditioner in the summer.

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We use large quantities of water. We drink it, wash with it, use it in industry, and also prepare food with it. Below are the percentage of the water that each person uses every day for these activities.

Drinking:

Only a 0.2% of the water a person uses every day is for drinking. Your drinking water comes from natural sources that are either groundwater or surface water.

Groundwater comes from rain and snow that seeps into the ground. The water gets stored in open spaces and pores or in layers of sand and gravel known as aquifers. We use water wells or springs to harvest this groundwater.

Surface Water also comes from rain and snow. It is the water that fills the rivers, lakes, and streams.

Personal:

Nearly 4.2% of the water a person uses for washing, cleaning your teeth, and flushing the toilet use up this share. Water generally gets to our homes in one of two ways. Either it is delivered by a city/county water department (or maybe from a private company), or people supply their own water, normally from a well. Water delivered to homes is called “public-supplied deliveries” and water that people supply themselves is called “self supplied”, and is almost always from groundwater.

Manufactured goods:

Nearly 30.6% of water a person use for manufactured goods. The industries that produce metals, wood and paper products, chemicals, gasoline and oils, and those invaluable grabber utensils you use to get your ring out of the garbage disposal are major users of water. Probably every manufactured product uses water during some part of the production process. Industrial water use includes water used for such purposes as fabricating, processing, washing, diluting, cooling, or transporting a product; incorporating water into a product; or for sanitation needs within the manufacturing facility. Some industries that use large amounts of water produce such commodities as food, paper, chemicals, refined petroleum, or primary metals.

Food production:

This takes up most of the water we use. Water is an essential part of our diet. Without it, our bodies would not work! For vegetative growth and development plants require water in adequate quantity and at the right time. Crops have very specific water requirements, and these vary depending on local climate conditions. The production of meat requires between six and twenty time more water than for cereals. 

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Earth’s water is always moving from one place to another. This process, called the water cycle, is a continuous journey, in which water moves between the land, the atmosphere, and the ocean.

The water cycle shows the continuous movement of water within the Earth and atmosphere. It is a complex system that includes many different processes. Liquid water evaporates into water vapor, condenses to form clouds, and precipitates back to earth in the form of rain and snow. Water in different phases moves through the atmosphere (transportation). Liquid water flows across land (runoff), into the ground (infiltration and percolation), and through the ground (groundwater). Groundwater moves into plants (plant uptake) and evaporates from plants into the atmosphere (transpiration). Solid ice and snow can turn directly into gas (sublimation). The opposite can also take place when water vapor becomes solid (deposition). 

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Most of the water on Earth is in the ocean – in fact, nearly 97%. The remaining 3% is freshwater and is stored in ice sheets, ice caps and glaciers, groundwater, and surface water such as lakes and rivers. The majority of this freshwater is frozen and stored in the Antarctic and Greenland ice sheets. Glaciers around the world are changing rapidly. In general, freezing and melting are a natural part of the water cycle, but for glaciers, more ice is melting each summer than falls as snow during the winter, and they are shrinking in size as a result. Glaciers also provide water resources, like drinking water, for downstream communities, but as the size of these glaciers changes, so too does this important resource.

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Water is essential to life on Earth. Without it, plants and animals would not be able to survive. Around 71 per cent of Earth is covered in water in water. This includes both salt water and fresh water. Not all of Earth’s water is easily available for us to use.

The water is concentrated at the Earth’s surface, so its relative mass compared to the whole Earth is small. It amounts to about 0.02 % of Earth’s mass!

The largest drop here represents the volume of all water, the mid sized drop freshwater, and the smallest drop (near Atlanta) all of Earth’s lake water.

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Over thousands of years, many different natural features, or landforms, have developed in deserts. A desert landform is a place that gets little to no rain. The climate can be either hot or cold and sometimes both. Each desert landform has one thing in common; it has less than 10 inches of rain per year. Usually deserts have a lot of wind because they are flat and have no vegetation to block out the wind.These include hills; mountains; narrow, steep-sided valleys called canyons; large, flat areas called plains; sand dunes; strange rock formations; and oases.

1. Sand dunes: These hills are formed by the wind blowing across the desert sand, so that it piles up. The most common in deserts include barchans and seif dunes. Barchan dunes are formed due to the wind action resulting in crescent-shaped dunes. These small crescent-shaped sand bodies form in locations where the wind blows consistently from one direction. Seif dunes, on the other hand, are long and narrow with a sharp crest common in the Sahara. They can also form a long chain of dunes.

2. Oases: Rare underground water can create pools of water. Plants then spring up around them. Oases typically occurs in the middle of a desert. They are fertile areas of the desert consisting of one or multiple springs surrounded by vegetation. Oasis is formed due to a mix of extreme temperatures resulting in islands of life. This comes about because the oases is situated in parts of the desert where the elevation is so low that the water table is just near the surface enabling vegetation to flourish.

3. Mesas and buttes: A mesa is a hill with steep sides and a flat top. A smaller mesa is sometimes called a butte. These landforms can also be called table mountains or table hills, because the word mesa actually means table in Spanish.

Scientists believe that mesas and buttes were formed when streams or rivers weathered and eroded away the smaller, softer rocks, leaving only the strong rock of the mesa or butte behind.

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These are extremely dry and cold. Temperatures rarely rise above 10° C (50° F), even in summer. Some are covered in ice and snow all year, while others are covered in gravel and large rocks. Most of Antarctica is polar desert.

Ross Island is located in Ross Sea, Antarctica and in McMurdo Sound. Due to the persistent presence of ice sheet, the isle is sometimes taken to be part of mainland Antarctica. The island is 43 miles (69 km) long and 45 miles wide. On it are Mount Erebus (an active volcano 12,450 feet [3,800 metres] high) and Mount Terror (10,750 feet) among a series of mountain ranges intersected by deep valleys. Mount Erebus was the site in 1979 of a crash that claimed 257 lives on a sightseeing and photographic flight over Antarctica. The ranges are free of snow except for hanging glaciers on the highest slopes. McMurdo, a U.S. base, is located on the island just north of Cape Armitage, its southernmost extremity. About one mile south is Scott Base, a New Zealand station. A steep pyramid of rock called Observation Hill rises between the two stations. In 1907 Ernest Shackleton, a British explorer, established a camp at Camp Royds, and Robert Falcon Scott, in 1910, set up a camp at Cape Evans on his return expedition. These are now maintained as historic monuments.

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Here, cold winds blowing off the ocean cause thick fog to form and drift inland. Water droplets in the fog soon dry up under the hot Sun, rather than falling as rain, leaving the land below very dry.

The Atacama Desert is one of the driest places on Earth. The Atacama is in the country of Chile in South America. In an average year, much of this desert gets less than 1 millimeter (0.04 inch) of rain! That makes it 50 times drier than Death Valley in California.

It is hard to survive in the Atacama Desert. Few people, animals, plants, or even microbes live there. But the desert isn’t completely without life. Some people and other living creatures do get by in the Atacama.

The north end of the Atacama Desert is near the border of Chile and Peru. It runs about 1,000 km (600 miles) south from there. It has an area of 140,000 km (54,000 square miles). That is about the size of the state of New York in the U.S.A.

The Atacama is the driest hot desert in the world. There are some weather stations in the Atacama where there has never been any rain! Not all deserts are hot. The Dry Valleys in Antarctica are cold deserts. They are the driest deserts on Earth.

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The largest cold deserts are in Central Asia, usually in high, flat areas. They are very dry, like all deserts, but are also very cold for most of the time. During the long winters, temperatures often drop as low as -40° C (-40° F).

Gobi, also called Gobi Desert, great desert and semidesert region of Central Asia. The Gobi (from Mongolian Gobi, meaning “waterless place”) stretches across huge portions of both Mongolia and China.The Gobi is overall a cold desert, with frost and occasionally snow occurring on its dunes. Besides being quite far north, it is also located on a plateau roughly 910–1,520 metres (2,990–4,990 ft) above sea level, which contributes to its low temperatures. An average of approximately 194 millimetres (7.6 in) of rain falls annually in the Gobi. Additional moisture reaches parts of the Gobi in winter as snow is blown by the wind from the Siberian Steppes. These winds may cause the Gobi to reach ?40° C (?40° F) in winter to 45° C (113° F) in summer.

However, the climate of the Gobi is one of great extremes, combined with rapid changes of temperature of as much as 35° C (63° F). These can occur not only seasonally but within 24 hours.

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Temperatures often reach 50° C (122° F) or higher during the day in hot deserts. But at night, it can be very cold. Most hot deserts are near the equator, where there is strong sunlight all year round.

The Sahara is the largest hot desert in the world, and the third largest desert behind Antarctica and the Arctic, which are both cold deserts. The Sahara is one of the harshest environments on Earth, covering 3.6 million square miles (9.4 million square kilometers), nearly a third of the African continent, about the size of the United States (including Alaska and Hawaii).

The Sahara desert has a variety of land features, but is most famous for the sand dune fields that are often depicted in movies. The dunes can reach almost 600 feet (183 meters) high but they cover only about 15 percent of the entire desert. Other topographical features include mountains, plateaus, sand- and gravel-covered plains, salt flats, basins and depressions. Mount Koussi, an extinct volcano in Chad, is the highest point in the Sahara at 11,204 feet (3,415 m), and the Qattara Depression in Egypt is the Sahara’s deepest point, at 436 feet (133 m) below sea level.

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About third of Earth’s surface is covered by deserts. They are areas that get little or no rain, so they are extremely dry. Only a few species of animals and plants can survive in them. We usually think of deserts as very hot places, but some are very cold.

Deserts are formed by weathering processes as large variations in temperature between day and night put strains on the rocks which consequently break in pieces. Although rain seldom occurs in deserts, there are occasional downpours that can result in flash floods. Rain falling on hot rocks can cause them to shatter and the resulting fragments and rubble strewn over the desert floor are further eroded by the wind. This picks up particles of sand and dust and wafts them aloft in sand or dust storms. Wind-blown sand grains striking any solid object in their path can abrade the surface. Rocks are smoothed down, and the wind sorts sand into uniform deposits. The grains end up as level sheets of sand or are piled high in billowing sand dunes. Other deserts are flat, stony plains where all the fine material has been blown away and the surface consists of a mosaic of smooth stones. These areas are known as desert pavements and little further erosion takes place. Other desert features include rock outcrops, exposed bedrock and clays once deposited by flowing water. Temporary lakes may form and salt pans may be left when waters evaporate. There may be underground sources of water in the form of springs and seepages from aquifers. Where these are found, oases can occur.

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Southern Peru 2001

The 2001 southern Peru earthquake occurred at 20:33:15 UTC (15:33:15 local time) on June 23 with a moment magnitude of 8.4 and a maximum Mercalli intensity of VIII (Severe).

At least 74 people were killed, including 26 killed by a tsunami. At least 2,687 were injured, 17,510 homes were destroyed and 35,549 homes damaged in the Arequipa-Camana-Tacna area. An additional 64 people were missing due to the tsunami in the Camana-Chala area. Landslides blocked highways in the epicentral area. Many of the historic buildings in Arequipa were damaged or destroyed, including the left tower of the Basilica Cathedral of Arequipa.

Denali 2002

The 2002 Denali earthquake occurred at 22:12:41 UTC (1:12 PM Local Time) November 3 with an epicenter 66 km ESE of Denali National Park, Alaska, United States. This 7.9 Mw earthquake was the largest recorded in the United States in 37 years (after the 1965 Rat Islands earthquake). 

Minor damage was reported over a wide area but the only examples of severe damage were on highways that crossed the fault trace and areas that suffered liquefaction, e.g. Northway Airport. Several bridges were damaged but none so severely that they were closed to traffic.

Hokkaid? 2003

The 2003 Hokkaid? earthquake, scientifically named the 2003 Tokachi-Oki earthquake, occurred off the coast of Hokkaid?, Japan on 26 September at 04:50 local time.

 The tremor affected a total of 36 local rivers, including the major Abashiri and Ishikari Rivers. Many properties received considerable damage, and although there were no deaths, 849 people sustained injuries.

Sumatra 2004

Ans: This massive earthquake had a force of 9.3! It triggered a series of huge waves, called for thousands of kilometers across the Indian Ocean, killing 280,000 people. The resulting tsunami affected 12 nations around the Indian Ocean, with Indonesia suffering the greatest damage. In Aceh, the northern province of Sumatra, the United Nations (UN) Field Office reported approximately 131,000 people confirmed dead and 37,000 missing. With more than 80,000 houses sustaining major damage or collapse, the UN estimated that more than 500,000 people were displaced from their homes in Sumatra alone. In addition to the massive damage to housing, utilities, roads, and bridges, the disaster significantly disrupted the social fabric and government of the affected communities.

Nias–Simeulue 2005

The 2005 Nias–Simeulue earthquake occurred on 28 March off the west coast of northern Sumatra, Indonesia. At least 915 people were killed, mostly on the island of Nias. The event caused panic in the region, which had already been devastated by the massive tsunami triggered by the 2004 Indian Ocean earthquake, but this earthquake generated a relatively small tsunami that caused limited damage. It was the third most powerful earthquake since 1965 in Indonesia.

On the Indonesian island of Nias, off the coast of Sumatra, hundreds of buildings were destroyed. The death toll on Nias was at least one thousand, with 220 dying in Gunungsitoli, the island’s largest town. Nearly half of Gunungsitoli’s population (27,000) fled.

Kuril Islands 2006

The 2006 Kuril Islands earthquake occurred on November 15 at 8:14:16 pm JST with an Mw magnitude of 8.3 and a maximum Mercalli intensity of IV (Light). This megathrust earthquake was the largest event in the central Kuril Islands since 1915 and generated a small tsunami that affected the northern Japanese coast. This earthquake is considered a doublet of the 2007 Kuril Islands earthquake that hit the same area on January 13, 2007.

Sumatra 2007

The September 2007 Sumatra earthquakes were a series of megathrust earthquakes that struck the Sunda Trench off the coast of Sumatra, Indonesia, with three of magnitude 7 or greater. A series of tsunami bulletins was issued for the area. The most powerful of the series had a magnitude of 8.4, which makes it in the top 20 of the largest earthquakes ever recorded on a seismograph.

It caused buildings to sway in Jakarta, and some buildings were reported to have collapsed in the city of Bengkulu, Bengkulu Province, about 100 km from the epicenter. The earthquake also led to a power outage in Bengkulu, which crippled communications. The death toll of the earthquakes is 21 with 88 people injured.

China 2008

 A force-8 earthquake struck Sichuan Province, China, in 2008. Huge chunks, of rock fell down from the mountains, smashing towns and villages. Tremors were felt up to 1,700 km (1,060 miles) away.

Almost 90,000 people were counted as dead or missing and presumed dead in the final official Chinese government assessment; the officially reported total killed included more than 5,300 children, the bulk of them students attending classes. In addition, nearly 375,000 people were injured by falling debris and building collapses. Hundreds of dams, including two major ones, were found to have sustained damage.

Italy 2009

In 2009, an earthquake measuring 6.3 on a seismograph struck L’Aquila in central Italy. Many buildings collapsed and around 300 people died. Thousands of smaller earthquakes, called aftershocks, followed.

By September 2009 vigorous assistance efforts had succeeded in moving some of the dispossessed into new homes, though thousands remained housed in temporary facilities. The town’s historic centre remained off-limits more than a year after the quake as restoration efforts proceeded slowly, and officials involved in the reconstruction effort were later investigated for wrongdoing in the awarding of public contracts.

Chile 2010

The 2010 Chile earthquake occurred off the coast of central Chile on Saturday, 27 February at 03:34 local time (06:34 UTC), having a magnitude of 8.8 on the moment magnitude scale, with intense shaking lasting for about three minutes. 

 According to official sources, 525 people lost their lives, 25 people went missing and about 9% of the population in the affected regions lost their homes.

Pacific coast of T?hoku 2011

The 2011 earthquake off the Pacific coast of T?hoku  was a magnitude 9.0–9.1 (Mw) undersea megathrust earthquake off the coast of Japan that occurred at 14:46 JST (05:46 UTC) on Friday 11 March 2011, with the epicentre approximately 70 kilometres (43 mi) east of the Oshika Peninsula of T?hoku and the hypocenter at an underwater depth of approximately 29 km (18 mi). 

 It was the most powerful earthquake ever recorded in Japan, and the fourth most powerful earthquake in the world since modern record-keeping began in 1900.

Indian Ocean 2012

The 2012 Indian Ocean earthquakes were magnitude 8.6 and 8.2 Mw? undersea earthquakes that struck near the Indonesian province of Aceh on 11 April at 15:38 local time.

Four people in their 60s and 70s in Banda Aceh, and a 39-year-old man in Lhokseumawe died from heart attacks or shock. Injuries were reported in Aceh Singkil, including a child who was critically injured by a falling tree. The quake prompted people in Indonesia, Thailand and India to leave their homes and offices in fear of tsunamis. 

Okhotsk Sea 2013

The 2013 Okhotsk Sea earthquake occurred with a moment magnitude of 8.3 at 15:44:49 local time (05:44:49 UTC) on 24 May. It had an epicenter in the Sea of Okhotsk and affected primarily (but not only) Asian Russia, especially the Kamchatka Peninsula where the shaking lasted for five minutes.

Iquique 2014

The 2014 Iquique earthquake struck off the coast of Chile on 1 April, with a moment magnitude of 8.2, at 20:46 local time (23:46 UTC).

Four men died of heart attacks and one woman was reportedly crushed to death when a wall collapsed. A loader was crushed by a falling metal structure and died of the injuries afterwards. Around 80,000 were displaced by the event. Electricity and water services were interrupted in the regions of Arica y Parinacota and Tarapacá.

Illapel 2015

The 2015 Illapel earthquake occurred 46 km (29 mi) offshore from Illapel (Coquimbo region, Chile) on September 16 at 19:54:33 Chile Standard Time (22:54:33 UTC), with a moment magnitude of 8.3. 

 Illapel, an inland city of some 30,000 residents, was reported immediately to be without electricity or drinking water. Two days after the quake, about 90,000 people were still without electricity. On September 21, officials were reporting over 9,000 people had been left homeless by the quake.

Ecuador 2016

At 18:58 ECT on April 16, a 7.8 Mw earthquake struck the coast of Ecuador approximately 27 km (17 mi) south-southeast of Muisne, in the province of Esmeraldas, at a depth of 20.6 km (12.8 mi). At least 676 people were killed and more than 16,600 others were injured in the earthquake. It was the worst natural disaster to hit Ecuador since the 1949 Ambato earthquake.

Chiapas 2017

The 2017 Chiapas earthquake struck at 23:49 CDT on 7 September (local time; 04:49 on the 8th UTC) in the Gulf of Tehuantepec off the southern coast of Mexico, near state of Chiapas, approximately 87 kilometres (54 mi) southwest of Pijijiapan (alternately, 101 kilometres (63 mi) south-southwest of Tres Picos), with a Mercalli intensity of IX (Violent).

 Within Chiapas, an estimated 1.5 million people were affected by the earthquake, with 41,000 homes damaged. Jose Calzada, Minister of Agriculture, reported that at least 98 people had died in the earthquake, including 78 in Oaxaca, 16 in Chiapas and 4 in Tabasco.

Fiji 2018

A powerful 8.2 magnitude earthquake occurred in the Pacific Ocean near the islands of Fiji and Tonga on Sunday morning local time, according to the United States Geological Survey (USGS). 

The epicentre of the quake was located 281 km northeast of the Ndoi Island in Fiji at a depth of 560 kilometres. Fiji is located in the Ring of Fire, an area in the basin of the Pacific Ocean, which is vulnerable to frequent earthquakes and volcanic eruptions.

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Earthquakes that a seismograph records as having a force of 2.5-4 are felt as mild tremors. They cause little or no damage, although trees may sway and windows rattle.

Earthquakes are the vibrations caused by rocks breaking under stress against an underground surface called a fault plane while a tremor is an involuntary movement of earth surface caused by stress in the underground rocks. They are both signs of seismic movement within the earth.

The rumblings being investigated belong to the tectonic tremor, a less hazardous form of seismic activity that occurs far deeper into the earth’s core than the devastating earthquakes that occur much closer to the earth’s surface.

One major difference between tectonic tremor and earthquakes is that tectonic tremor causes relatively weak ground shaking and is not cause for immediate concern.

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This machine is used to measure the force of the vibrations caused by an earthquake. It records how powerful these vibrations are on a numbered scale.

 They are held in a very solid position, either on the bedrock or on a concrete base. The seismometer itself consists of a frame and a mass that can move relative to it. When the ground shakes, the frame vibrates also, but the mass tends not to move, due to inertia. The difference in movement between the frame and the mass is amplified and recorded electronically.

A network of seismometers is used to calculate the magnitude and source of an earthquake in three dimensions

Seismographs are used to determine:

• Magnitude: the size of the earthquake
• Depth: how deep the earthquake was
• Location: where the earthquake occurred

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The plates in Earth’s crust constantly side past each other, but can get stuck. Pressures then builds up until the plates finally move, sending out shock waves. The focus of an earthquake is the point inside the ground where pressure builds up. The epicenter is the point on the surface above the focus.

The point at which this slippage occurs is called the FOCUS, whilst the point on the ground surface above the earthquake FOCUS is called the EPICENTRE. Seismic shock waves will emanate radially outwards from these points and their energy will reduce with distance. This is typical of destructive margins (which account for 90% of the World’s earthquakes) where the Oceanic plate grinds under a Continental plate (as on the East coast of Japan -see Kobe case study). They also occur at conservative margins, such as the San Andreas Fault line, where the North American plate and Pacific plate are grinding past one another.

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An earthquake can cause large cracks to open up in the Earth’s surface. Many are small, no more than a few metres deep or wide, but others are massive, and whole buildings can fall into them.

When an earthquake strikes, it will create fissures into the depths of the earth in random locations, usually with a lot of people. In reality, the ground often just shakes, shifts and quakes — the physical damage is usually to structures on the ground, not the ground itself. If fissures do open up, it is usually due to a landslide triggered by the quake, which means they’re restricted to hillsides, mountains, and cliffs. If you see roads with cracks and fissures and dislodged pieces, it is because the wet, sandy ground underneath has liquefied, causing the road to sink unevenly and crack. And yes, that can happen to buildings too.

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When the rocky tectonic plates that form Earth’s crust move suddenly, large waves of energy spread out, causing the ground to shake. This is an earthquake. Some earthquakes are fairly gentle and may even go unnoticed, but others can bring terrible destruction.

Sometimes an earthquake has foreshocks. These are smaller earthquakes that happen in the same place as the larger earthquake that follows. Scientists can’t tell that an earthquake is a foreshock until the larger earthquake happens. The largest, main earthquake is called the mainshock. Mainshocks always have aftershocks that follow. These are smaller earthquakes that occur afterwards in the same place as the mainshock. Depending on the size of the mainshock, aftershocks can continue for weeks, months, and even years after the mainshock!

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The magma chamber: This is the area with massive collection of magma below the earth’s crust from which magma flows out.

Crater: After an eruption, the tip or top of the volcano tends to get blown off, leaving a small depression at the top of it.

Main vent: This is the main exit point (opening or outlet) in a weak zone where molten magma is released to the surface.

Secondary vents: These are other smaller vents or opening through which ash and gases and lava escape.

Ashes, clouds and cinders: As the eruption continues, ashes and gases are discharged into the air, which is carried further by wind action.

Layers of ash and lava: The walls of a volcano are usually made up of solidified layers of lava and dust.

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Volcanoes form when magma a mixture of hot gas, ash, and melted rock-erupts from a crack in the Earth’s surface. The melted rock, called lava, flows out and hardens. As layers of lava build up, the volcano gets bigger. A volcano can be active, dormant, or extinct. Volcanoes can and have existed on other worlds as well: although volcanoes on the moon and Mars have long been dormant, volcanoes are still very active on Jupiter’s moon Io. Researchers are currently striving to find ways to predict when volcanic eruptions might happen on Earth by analyzing clues such as crystals and gases linked with volcanoes.

Stratovolcano

Stratovolcanoes are tall and cone-shaped, with steep sides. They are made up of lots of layers of lava and ash that have cooled and hardened. Their eruptions can be very powerful and dangerous.

Stratovolcanoes are also called composite volcanoes because they are built of layers of alternating lava flow, ash and blocks of unmelted stone, according to the U.S. Geological Survey. They are larger than cinder cones, rising up to 8,000 feet (2,438 meters). Stratovolcanoes result from a conduit system of vents leading from a magma reservoir beneath the surface. When dormant, they typically have steep concave sides that sweep together at the top around a relatively small crater.

Shield   

Shield volcanoes have gently sloping side and are formed from thin, runny lava. Their eruptions are less explosive and much less dangerous than other volcanoes. These gentle eruptions can continue for years. Eruptions of these volcanoes are not generally explosive, but are more like liquid overflowing around the edges of a container. The world’s largest volcano, Mauna Loa in Hawaii, is a shield volcano, according to the U.S. Geological Survey. Mauna Loa is about 55,770 feet (17,000 meters) from its base beneath the ocean to the summit, which is 13,681 feet (4,170 meters) above sea level. It is also one of the Earth’s most active volcanoes and is carefully monitored. The most recent eruption was in 1984.

Cinder Cone

Cinder cone volcanoes are the smallest and most common type of volcano. They are cone-shaped with steep sides. Their eruptions are usually not too violent. They may occur as single volcanoes or as secondary volcanoes known as “parasitic cones” on the sides of stratovolcanoes or shield volcanoes. Airborne fragments of lava, called tephra, are ejected from a single vent. The lava cools rapidly and fall as cinders that build up around the vent, forming a crater at the summit, according to the U.S. Geological Survey.

Caldera

Calderas are large, circular hollows, almost like a bowl. They form when a massive eruption forces most of the magma out of the chamber under the volcano, causing it to collapse. Craters are usually more circular than calderas. (Calderas may have parts of their sides missing because land collapses unevenly.) Craters are also usually much smaller than calderas, only extending to a maximum of one kilometer (less than a mile) in diameter. 

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Planes usually fly in the troposphere, but may go up to the edge of the stratosphere. Little moisture enters the stratosphere, so clouds are rare. Even though the stratosphere has complex wind systems, violent storms don’t occur there. Because the air temperature in the stratosphere slowly increases with altitude, it does not cause convection and has a stabilizing effect on atmospheric conditions in the region. Stability generally limits vertical extensions of cloud and leads to the lateral spreading of high cumulonimbus cloud with characteristic anvil heads. This means that weather (in the form of clouds) is almost entirely confined to the troposphere below. That’s why airline pilots prefer to fly in the stratosphere.

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This thin layer, running across the stratosphere, contains a large amount of ozone, a gas that absorbs ultraviolet (UV) rays from the Sun. UV rays cause sunburn, and can cause skin cancer.

Approximately 90 percent of the atmosphere’s ozone occurs in the stratosphere, the region extending from 10–18 km (6–11 miles) to approximately 50 km (about 30 miles) above Earth’s surface. In the stratosphere the temperature of the atmosphere rises with increasing height, a phenomenon created by the absorption of solar radiation by the ozone layer. The ozone layer effectively blocks almost all solar radiation of wavelengths less than 290 nanometres from reaching Earth’s surface, including certain types of ultraviolet (UV) and other forms of radiation that could injure or kill most living things.

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Scientists launch these to collect information about conditions in Earth’s atmosphere that affect the weather, such as temperature and air pressure. The balloons are made of rubber and weigh up to one kilogram.

The information collected from the instruments on weather balloons are used to learn about current weather conditions, to help meteorologists to make weather forecasts, and to collect data for other scientific research projects. Weather balloons carry instrument packages that are called radiosondes. Scientists have been using them since the 1930s.

To gather information for weather forecasts, weather balloons are launched twice a day, every day, from 800 locations around Earth. They are launched at the same time all over the world. The balloons rise more than 24.14 kilometers (15 miles) while collecting data.

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These are bits of matter from outer’s space that burn up on entering Earth’s atmosphere, creating streaks of light. They are also called shooting stars.

 A meteor is a meteoroid that has entered the earth’s atmosphere.

It will then become brightly visible due to the heat produced by the ram pressure.

If a meteor survives its transit of the atmosphere to come to rest on the Earth’s surface, the resulting object is called a meteorite.

A meteor striking the Earth or other object may produce an impact crater.

During the entry of a meteoroid into the upper atmosphere, an ionization trail is created, where the molecules in the upper atmosphere are ionized by the passage of the meteor.

Such ionization trails can last up to 45 minutes at a time.

Small, sand-grain sized meteoroids are entering the atmosphere constantly, essentially every few seconds in a given region, and thus ionization trails can be found in the upper atmosphere more or less continuously.

When radio waves are bounced off these trails, it is called meteor scatter communication.

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These bright lights appear in the thermosphere when particles from the Sun fall into Earth’s atmosphere. Auroras are produced when the magnetosphere is sufficiently disturbed by the solar wind that the trajectories of charged particles in both solar wind and magnetospheric plasma, mainly in the form of electrons and protons, precipitate them into the upper atmosphere (thermosphere/exosphere) due to Earth’s magnetic field, where their energy is lost.

The resulting ionization and excitation of atmospheric constituents emits light of varying color and complexity. The form of the aurora, occurring within bands around both Polar Regions, is also dependent on the amount of acceleration imparted to the precipitating particles. Precipitating protons generally produce optical emissions as incident hydrogen atoms after gaining electrons from the atmosphere. Proton auroras are usually observed at lower latitudes.

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These orbit Earth in the thermosphere and exosphere. We use them to make phone calls and watch TV. Scientists also use satellites to find out more about space.

Satellites come in many shapes and sizes. But most have at least two parts in common – an antenna and a power source. The antenna sends and receives information, often to and from Earth. The power source can be a solar panel or battery. Solar panels make power by turning sunlight into electricity.

Many NASA satellites carry cameras and scientific sensors. Sometimes these instruments point toward Earth to gather information about its land, air and water. Other times they face toward space to collect data from the solar system and universe.

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Mesosphere

The top of the mesosphere is the coldest part of the Earth’s atmosphere, with temperatures of -143°C (-226°F). Gases here are thick enough to slow down meteors, causing them to burn up. It extends upward to a height of about 85 km (53 miles) above our planet. Most meteors burn up in the mesosphere. Unlike the stratosphere, temperatures once again grow colder as you rise up through the mesosphere. The coldest temperatures in Earth’s atmosphere, about -90°C (-130°F), are found near the top of this layer. The air in the mesosphere is far too thin to breathe; air pressure at the bottom of the layer is well below 1% of the pressure at sea level, and continues dropping as you go higher.

Stratosphere

The air in this layer is very dry and still. The ozone layer, which protects plants and animals on Earth from dangerous ultraviolet (UV) rays that are given off by the Sun, lies in the stratosphere. The stratosphere extends from the top of the troposphere to about 50 km (31 miles) above the ground. The infamous ozone layer is found within the stratosphere. Commercial passenger jets fly in the lower stratosphere, partly because this less-turbulent layer provides a smoother ride. The jet stream flows near the border between the troposphere and the stratosphere.

Troposphere

The gases found in the troposphere make up the air that we breathe. Therefore life exists in this layer. Starting at ground level, it extends upward to about 10 km (6.2 miles or about 33,000 feet) above sea level.Clouds form here, and it is where most of our weather occurs, mainly because 99% of the water vapor in the atmosphere is found in the troposphere. Air pressure drops, and temperatures get colder, as you climb higher in the troposphere.

Thermosphere

Unlike in other layers of Earth’s atmosphere, temperatures here increase as you go higher, some parts rising to 2000°C (3,600°F)! High-energy X-rays and UV radiation from the Sun are absorbed in the thermosphere, raising its temperature to hundreds or at times thousands of degrees. However, the air in this layer is so thin that it would feel freezing cold to us! In many ways, the thermosphere is more like outer space than a part of the atmosphere. Satellites, including the International Space Station, orbit Earth in the thermosphere.

Exosphere

This is the highest layer of Earth’s atmosphere, where it merges into space. Only a few, very thin wisps of gas are found this high above our planet. It would be impossible to breathe here! In fact, air in the exosphere is constantly – though very gradually – “leaking” out of Earth’s atmosphere into outer space. There is no clear-cut upper boundary where the exosphere finally fades away into space. Different definitions place the top of the exosphere somewhere between 100,000 km (62,000 miles) and 190,000 km (120,000 miles) above the surface of Earth.

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Earth is surrounded by thick layer of gases, called the atmosphere. These gases protect Earth from the Sun’s rays, keeping temperatures on our planet at a comfortable level. Earth’s atmosphere is divided into a number of distinct layers. At the outer edge of the atmosphere, there is no clear boundary. It just fades into space.

Earth’s atmosphere is about 300 miles (480 kilometers) thick, but most of it is within 10 miles (16 km) the surface. Air pressure decreases with altitude. At sea level, air pressure is about 14.7 pounds per square inch (1 kilogram per square centimeter). At 10,000 feet (3 km), the air pressure is 10 pounds per square inch (0.7 kg per square cm). There is also less oxygen to breathe.

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This is an imaginary line around which the Earth spins as it travels around the Sun. Earth’s axis is slightly tilted. This is what is known axial tilt, where a planet’s vertical axis is tilted a certain degree towards the ecliptic of the object it orbits (in this case, the Sun). Such a tilt results in there being a difference in how much sunlight reaches a given point on the surface during the course of a year. In the case of Earth, the axis is tilted towards the ecliptic of the Sun at approximately 23.44° (or 23.439281° to be exact).

This tilt in Earth’s axis is what is responsible for seasonal changes during the course of the year. When the North Pole is pointed towards the Sun, the northern hemisphere experiences summer and the southern hemisphere experiences winter. When the South Pole is pointed towards the Sun, six months later, the situation is reversed.

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This is an imaginary line around the middle of the Earth. It lies halfway between the North and South Poles, at 0 degrees latitude. An equator divides the planet into a Northern Hemisphere and a Southern Hemisphere.

The Earth is widest at its Equator. The distance around the Earth at the Equator, its circumference, is 40,075 kilometers (24,901 miles). 

The Earth’s diameter is also wider at the Equator, creating a phenomenon called an equatorial bulge. The diameter of a circle is measured by a straight line that passes through the center of the circle and has its endpoints on the boundary of that circle. Scientists can calculate the diameter of latitudes, such as the Equator and Arctic Circle.

The Earth’s diameter at the Equator is about 12,756 kilometers (7,926 miles). At the poles, the diameter is about 12,714 kilometers (7,900 miles). The Earth’s equatorial bulge is about 43 kilometers (27 miles). 

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This is the path that the Earth takes as it travels around the Sun. Earth’s orbit does not form a perfect circle. It is a slightly flattened circle, or oval. Earth takes 365 days, or a whole year, to make one complete journey around the Sun.

As seen from Earth, the planet’s orbital prograde motion makes the Sun appear to move with respect to other stars at a rate of about 1° (or a Sun or Moon diameter every 12 hours) eastward per solar day. Earth’s orbital speed averages about 30 km/s (108,000 km/h; 67,000 mph), which is fast enough to cover the planet’s diameter in 7 minutes and the distance to the Moon in 4 hours.

From a vantage point above the north pole of either the Sun or Earth, Earth would appear to revolve in a counterclockwise direction around the Sun. From the same vantage point, both the Earth and the Sun would appear to rotate also in a counterclockwise direction about their respective axes.

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Our solar system is made up of the Sun and the eight planets that travel around it- Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. The solar system also has moons, comets, asteroids, and meteoroids zipping through it. Scientists estimate that our solar system was formed about 4.6 billion years ago!

The Sun’s nearest known stellar neighbor is a red dwarf star called Proxima Centauri, at a distance of 4.3 light years away. The whole solar system, together with the local stars visible on a clear night, orbits the center of our home galaxy, a spiral disk of 200 billion stars we call the Milky Way. The Milky Way has two small galaxies orbiting it nearby, which are visible from the southern hemisphere. They are called the Large Magellanic Cloud and the Small Magellanic Cloud. The nearest large galaxy is the Andromeda Galaxy. It is a spiral galaxy like the Milky Way but is 4 times as massive and is 2 million light years away. Our galaxy, one of billions of galaxies known, is traveling through intergalactic space.

The planets, most of the satellites of the planets and the asteroids revolve around the Sun in the same direction, in nearly circular orbits. When looking down from above the Sun’s North Pole, the planets orbit in a counter-clockwise direction. The planets orbit the Sun in or near the same plane, called the ecliptic. Pluto is a special case in that its orbit is the most highly inclined (18 degrees) and the most highly elliptical of all the planets. Because of this, for part of its orbit, Pluto is closer to the Sun than is Neptune. The axis of rotation for most of the planets is nearly perpendicular to the ecliptic. The exceptions are Uranus and Pluto, which are tipped on their sides.

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Earth is our home. It is nearly 150 million km (94 million miles) from the Sun, and is the fifth largest planet in our solar system.  Its diameter is about 8,000 miles. And Earth is the third-closest planet to the sun. Its average distance from the sun is about 93 million miles. Only Mercury and Venus are closer.

Earth has been called the “Goldilocks planet.” In the story of “Goldilocks and the Three Bears,” a little girl named Goldilocks liked everything just right. Her porridge couldn’t be too hot or too cold. And her bed couldn’t be too hard or too soft. On Earth, everything is just right for life to exist. It’s warm, but not too warm. And it has water, but not too much water.

Earth is also the only planet in our solar system where water is found on the surface, which allows animals and plants to live there.

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               Caves have for long been linked with the history of civilization in many interesting ways. In the stone age, men used to live in caves to protect themselves from cold and animals. Ancient people had many strange notions about caves. The people of Greece believed that their gods Zeus, Pan, Dionsus and Pluto lived in caves. The Romans believed that caves were the homes of nymphs and sibyls. People of Persia worshipped caves considering them to be the abodes of God. Today, huge and beautiful caves all over the world have become centres of attraction for the tourists. Do you know how these caves were formed?

               A cave is a deep hollow space in a mountain. It is formed in different ways. When water waves coming from the sea, collide with the mountains, they wash away the soft stones present in between the layers of the rocks. This process continued over a period of thousands of years and created large spaces inside the mountains which we call caves.

               Some caves are found below the Earth’s surface also. These have been formed by the water streams flowing below the Earth’s surface. The underground water streams wash away the lime-stone from the rocks and the voids so created are called caves.

               Quite often, waterfalls create hollow spaces within the rocks which ultimately become caves. Such caves have been formed below the Niagara Falls.

               Caves are also formed by the volcanic changes taking place in the earth’s layers. Some caves are very long while some are very deep. The deepest cave is ‘Guffre de la piere st.’ situated on the border of France and Spain. It is 1310 metres (4300 ft) deep. The longest cave, ‘Flit Ridge cave system’ is situated in America and is 116.8 km (73 miles) long.

               The longest single cavern in the world is the Sarawak chamber in Eastern Malaysia. It is 700 metres long and was discovered in 1980. Mammoth Cave National Park in the US State of Kentucky is the largest cave system of the world about 307 km long. In India, caves of Ajanta and Ellora are famous for their beautiful sculptures. 

            A volcano is a mountain having an opening on the surface of the Earth from which fire, smoke and ashes come out continuously. Mountains of this type are created by upheavals inside the Earth.

            The formation of volcanoes can be understood as follows. Temperature inside the Earth goes on increasing as we go into the interior of the Earth. At a depth of approximately 30 km, the temperature is so high that it can melt rocks. When rocks inside the Earth get melted, they start expanding. These molten rocks are known as magma. In some parts of the Earth, this magma starts coming up through openings in the Earth’s crust. When the pressure exerted by this magma is considerably high and the Earth’s crust at some places is weak, the crust breaks at those places and, as a result, hot gases, liquid and solid material of the red molten rocks start coming out. This is called volcanic eruption. The ejected hot smoke, ashes and stone pieces constitute what we call lava. This lava goes on solidifying in the shape of a cone and, on cooling; it takes the form of a mountain on the surface of the Earth.

            Fire and smoke keep on flowing out of the opening of the volcano until the molten material inside the Earth is exhausted. Such volcanoes from which lava stops coming are called dead volcanoes. There are more than 450 volcanoes in the world. The number of volcanoes in Indonesia is quite large. The highest dead volcano of the world is in Argentina; it is 6,960 metres high. One of the most violent volcanic eruptions was on the island of Krakatau, near Sumatra in 1883 which produced tidal waves in the oceans throughout the world.

            Earthquakes are common occurrences. We often read about them in newspapers or listen over the radio. Do you know how they are caused?

            When an earthquake occurs, that particular part of the Earth experiences tremors. Sometimes it is so mild that it passes unnoticed. But, often, it is quite strong and creates vast openings in the Earth’s surface – buildings fall down and many lives are lost.

            We know that the Earth’s surface is composed of various kinds of high and low rocks. Due to the internal upheavals of the Earth or the uneven pressure, malformation sets in the rocks. Due to the excessive pressure, the layers of rocks crack suddenly. After breaking, they either go up or down inside the Earth. At the places where such changes take place in the rocks, the Earth’s crust experiences big shocks. These shocks cause vibrations which spread through the Earth’s surface. All those areas through which these vibrations travel are said to be affected by an earthquake and, as a result of these vibrations, buildings fall down and lives are lost. The point of origin of an earthquake is called the epicentre of the earthquake. 

            Some places on the Earth are prone to earthquakes. Japan has the highest incidence of earthquakes. The Earth surface in Japan is uneven throughout and so the occurrence of earthquakes is very common there.

             San Francisco, Lisbon, China, India and Japan have all suffered great loss of lives and property from the occurrence of earthquakes.

            Scientists have developed an instrument called the seismograph to study earthquakes. This instrument has arrangements to study the seismic waves caused by the earthquakes. Seismographs have been installed at various places in the world to record the seismic vibrations with a view to help mankind from the dangers of earthquakes. But it is impossible to forecast an earthquake or prevent it from happening.

           Lakes are large masses of water formed mainly in low-lying areas of the Earth. Their main sources are rain-water or molten snow or, at times, a small river or a stream. Do you know how these lakes are formed? 

                                                                                                 Lakes are formed in many ways. Some lakes lie in the natural hollow of an old volcano. For example, the crater lake of Oregon in South America. Due to some upheavals, like falling of a meteor large ditches were formed on the surface of the earth, which later got filled with rain water – for example, Lake Bosuntui in Ashanti crater in Ghana.

                                                                                                                                                                                       The Glacial lakes are formed because the sliding glaciers cause big ditches on the Earth’s surface which become lakes after rain-water and molten snow accumulates there. The Winnipeg Lake of Canada was formed by glaciers.

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            Sometimes a stream of water suddenly bursts out from an opening in the Earth in the form of a fountain. This is called a spring. Springs generally erupt out of rocks. Springs are of cold water usually but some are hot springs or sulphur springs.

            When it rains, the Earth absorbs a part of the rain-water while the remaining water gets evaporated. Due to the Earth’s gravitational force, the water so absorbed keeps on going down through the holes and cracks in the Earth. And, when this water encounters some rocks on the way, it accumulates there. When this accumulated water finds an opening to come out, it bursts out as a spring. They are often found where permeable rocks lie above impermeable one, particularly in low lying areas. 

            Sometimes the water accumulated inside the Earth has to pass through sections containing sulphur and lime. The sulphur and lime dissolve in water and when this water comes out in the form of a spring, it contains sulphur. Hence, water of such springs has the smell of sulphur and they are called sulphur springs. In India, there are many such springs in Kashmir, Haryana and Uttar Pradesh.

                                                                                                Sometimes water from the Earth’s surface reaches deep down in the Earth’s interior. It then starts boiling due to the Earth’s heat. When it comes out through such opening in the Earth in the form of a spring, its water is hot. Such springs are called hot springs. There are many such springs in the United States of America and New Zealand.

          A body of water falling down from a mountain rock is known as a waterfall. If water falls from a great height in the form of a large stream, it is called a cataract. But if the falling stream is narrow, it is called a cascade.

          It is essential for the formation of a waterfall that water flows through certain hard rocky areas. Hard rocks should be followed by soft soil which water can easily cut through. At some places, due to natural changes, the river flows through areas which are higher than the sea level and thus water falls from a height. Sometimes flow of the river is obstructed by landslides. Water accumulates there and later falls down in the form of a waterfall. There are many kinds of waterfalls at many hilly places.

             The Angel waterfall of Venezuela in South America is the highest waterfall of the world. Here water falls from a height of 1000 metres. This was discovered in 1835 by Jimmy Angel, pilot of the US.

            The highest waterfall of Asia is the Gersoppa waterfall in India. The Niagara waterfall is also world-famous for many reasons. Situated 25 km Northwest of New York in the U.S.A., this waterfall of Niagara River is divided into two parts. One part is in the possession of the U.S.A., while the other is in possession of Canada. This waterfall actually acts as the international boundary between these two countries.

            The Ribbon waterfall of California in America is the highest narrow-stream waterfall of the world. A narrow stream falls into the Merced River from a height of 490 metres. The widest waterfall of the world is the Khoni waterfall having a width of 11 km.

            Some waterfalls have proved very useful to man. Hydro-electricity produced from waterfalls is used for innumerable purposes. 

            Glacier is a large mass of moving ice. We see glaciers in various mountain ranges and vallies of the world. In the Alps alone there are as many as 1,200 glaciers. In the high mountains of the Alaska, there are around thousands of glaciers with length, ranging from 30 to 60 kilometres.

            The process for the formation of glaciers is described below. During snowfall snow slides down on the slopes of mountains. After a considerable time it accumulates in big quantities. As this accumulated snow does not melt even in summers, its quantity keeps on increasing. As the quantity of snow increases, the pressure on the lowest layer of the snow also increases. Due to the increased pressure and other atmospheric effects, air leaks out from the lowest layer of snow and consequently, it becomes hardened. This process goes on till a time comes when glaciers become heavy enough to flow downhill under their own weight.

            Glaciers are mainly of two kinds. The first type is the valley glaciers. When there is snowfall on the mountains, the snow slides down on the slopes. This gets deposited in the spaces between the mountains. When snow accumulates in big quantities, it often starts sliding down. The slow moving river of ice is called the valley glacier. Large chunks of stones coming in the way of this river move forward with this river and break into pieces due to friction and collisions with other stones. They spread uniformly in all directions. The motion of the glacier thus forms valleys.

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       Everybody knows that sea water is salty. This means that some salt in the dissolved form is present in sea water. One gallon of sea water contains about one hundred grams of salt. In general sea water has 4% to 6% salt in it. In comparison to open seas, the quantity of salt in closed seas like the Mediterranean and the Red Sea is more. If salt of all the oceans is collected and dried, one can make a 288 km high and 1.6 km thick wall with this salt, which will be long enough to encircle the entire perimeter of the Earth along the equator.

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         About three-fourth of the Earth’s total surface is covered with water. Only one-fourth of Earth’s surface is land. The total area of the Earth’s surface covered by oceans comes to 361.100 million sq. km. Do you know how and when these oceans were formed?

          It is not yet fully known when oceans were formed. However, at the beginning of the formation of Earth, there were no oceans. The age of oceans has been calculated on the basis of the minerals present inside them. It is estimated that oceans were formed some time between 500 to 1,000 millions years before.

            The story of the origin of oceans is very interesting. The Earth was a giant burning fire ball at the time of its birth. Its surface was formed by molten rocks. When the Earth started cooling slowly, it was enveloped by clouds of gases. These clouds became very heavy after cooling. They started raining heavily, but the Earth’s surface was still so hot that the raindrops falling on it would evaporate and mix with the atmosphere again. This would again come down to the Earth in the form of rains. This cycle continued for millions of years. The Earth’s crust became cold and tough and the rain-water would boil no more, but the heavy down-pour continued for thousands of years. The low-lying areas of the Earth were filled up with the water of these heavy rains. These vast lakes of water on the surface of the Earth are today’s oceans. 

          Dead Sea is the only sea on earth which has no plant or animal life. It is, therefore, appropriately called Dead Sea. In fact, Dead Sea is a saline lake situated between Jordan and Israel. This is 77 km long and its breadth ranges between 5 to 18 kilometres. The water level of Dead Sea is the lowest on the Earth. It is lower than the sea-level by 396 metres. Millions of years ago the level of Dead Sea was, however, higher than the present one by 427 metres. At that time aquatic animals were living in Dead Sea. All of a sudden, there was a draught and the water of this sea evaporated. Gradually this sea acquired the present state.

          No river originates from this sea. The Jordan River and some small canals end up in this sea. Since no river comes out of this, the water of this sea depletes only by evaporation. Consequently, the amount of salt and other soluble minerals brought into the sea by the Jordan River and other smaller canals goes on increasing. You will be surprised to know that the amount of salt present in Dead Sea is the largest in comparison to the other seas. In general, the amount of salt present in any sea is 4% to 6%. But even this make you sick as it contains large quantities of magnesium chloride and other poisonous substances. Due to the presence of large quantities of salt and other poisonous materials no living being can survive in this sea. Hence fish and other acquatic animals of the Jordan River die as soon as they enter the water of this sea.

          Generally, Sea Mountains are those mountains which are at least one kilometre above the seabed. A number of such mountains have been discovered.

          Upheavals at the bottom of the sea are responsible for the formation of these mountains. Volcanic eruptions in the seabed also make mountains. Generally, these mountains are one to three kilometres high. Majority of these mountains remain submerged in water, but some of them have surfaced above also. The flat mountains coming above water are called islands. The Hawaii islands were formed in this manner.

          There are many mountains in the midst of oceans. The mid-ocean ridge is continuous and it winds for 60,000 km through all worlds’ oceans. There are many mountains in the north-east part of the Pacific Ocean. Most of these mountains are submerged in water, but some of the mountains of the Hawaiian chain have surfaced above. They are called the Hawaii Islands. The highest mountain of the Hawaiian chain is the Mauna Kea. The height of this mountain is 4,200 metres above sea level, but the total height of this mountain from the bottom of the sea is 9,686 metres. That means the height of this mountain inside the sea is 5,486 metres. If its height is taken in full, this is the highest mountain of the world.