Category Science

          The Earth began to be formed over 4.5 billion years ago, but for millions of years nothing could live here. Gradually, the Earth’s crust and the atmosphere formed. The simplest forms of life, bacteria and algae, probably began to grow less than four billion years ago. Human beings did not appear until about two million years ago.

          Microbial life forms have been discovered on Earth that can survive and even thrive at extremes of high and low temperature and pressure, and in conditions of acidity, salinity, alkalinity, and concentrations of heavy metals that would have been regarded as lethal just a few years ago. These discoveries include the wide diversity of life near sea–floor hydrother­mal vent systems, where some organisms live essentially on chemical energy in the absence of sunlight. Similar environments may be present elsewhere in the solar system.

          Under­standing the processes that lead to life, however, is complicated by the actions of biology itself. Earth’s atmosphere today bears little resemblance to the atmosphere of the early Earth, in which life developed; it has been nearly reconstituted by the bacteria, vegetation, and other life forms that have acted upon it over the eons. Fortunately, the solar system has preserved for us an array of natural laboratories in which we can study life’s raw ingredients — volatiles and organics — as well as their delivery mechanisms and the prebiotic chemical processes that lead to life. We can also find on Earth direct evidence of the interactions of life with its environments, and the dramatic changes that life has undergone as the planet evolved. This can tell us much about the adaptability of life and the prospects that it might survive upheavals on other planets.

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          One interesting aspect of volcanic eruptions is that surrounding areas are covered rapidly in molten rock or ash, sometimes preserving the animals, plants and structures underneath. Archaeologists have been able to study life in Roman times, for example, by examining the remains of Pompeii, in Italy, buried when Vesuvius erupted in AD 79.

          I guess the main good effect that volcanoes have on the environment is to provide nutrients to the surrounding soil. Volcanic ash often contains minerals that are beneficial to plants, and if it is very fine ash it is able to break down quickly and get mixed into the soil.

          Perhaps the best place to look for more information about this would be to look up references about some of the countries where lots of people live in close proximity to volcanoes and make use of the rich soils on volcanic flanks. These would include Indonesia, The Philippines, Japan, Italy, etc.

          I suppose another benefit might be the fact that volcanic slopes are often rather inaccessible, especially if they are steep. Thus they can provide refuges for rare plants and animals from the ravages of humans and livestock.

          Finally, on a very fundamental scale, volcanic gases are the source of all the water (and most of the atmosphere) that we have today. The process of adding to the water and atmosphere is pretty slow, but if it hadn’t been going on for the past 4.5 billion years or so we’d be pretty miserable.

          Volcanoes have done wonderful things for the Earth. They helped cool off the earth removing heat from its interior. Volcanic emissions have produced the atmosphere and the water of the oceans. Volcanoes make islands and add to the continents.

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          Like earthquakes, volcanoes mainly occur along fault lines. Molten rock, gases and ash are forced out through a gap in the Earth’s crust to release the pressure beneath. Over thousands of years, cooled rock sometimes builds up around the fissure in the ground to form the familiar conical shape of a volcano.

          Deep within the Earth it is so hot that some rocks slowly melt and become a thick flowing substance called magma. Since it is lighter than the solid rock around it, magma rises and collects in magma chambers. Eventually, some of the magma pushes through vents and fissures to the Earth’s surface. Magma that has erupted is called lava.

          Some volcanic eruptions are explosive and others are not. The explosivity of an eruption depends on the composition of the magma. If magma is thin and runny, gases can escape easily from it. When this type of magma erupts, it flows out of the volcano. A good example is the eruptions at Hawaii’s volcanoes. Lava flows rarely kill people because they move slowly enough for people to get out of their way. If magma is thick and sticky, gases cannot escape easily. Pressure builds up until the gases escape violently and explode. A good example is the eruption of Washington’s Mount St. Helens. In this type of eruption, the magma blasts into the air and breaks apart into pieces called tephra. Tephra can range in size from tiny particles of ash to house-size boulders.

          Explosive volcanic eruptions can be dangerous and deadly. They can blast out clouds of hot tephra from the side or top of a volcano. These fiery clouds race down mountainsides destroying almost everything in their path. Ash erupted into the sky falls back to Earth like powdery snow. If thick enough, blankets of ash can suffocate plants, animals, and humans. When hot volcanic materials mix with water from streams or melted snow and ice, mudflows form. Mudflows have buried entire communities located near erupting volcanoes.

Picture Credit : Google