Category Science

What is a Hydrogen Bomb?

          Soon after the development of the atom bomb in 1945 scientists started developing a more powerful bomb. As a result, they managed to develop another highly destructive bomb called the ‘hydrogen bomb’. The first hydrogen bomb was tested in 1952 by the American scientist Edward Teller and his team. It was a 10 megaton bomb, about 700 times more powerful than the atom bomb dropped in Hiroshima.

          The hydrogen bomb makes use of the phenomenon of ‘nuclear fusion’. In the fusion process, four hydrogen nuclei combine at extremely high temperature to form one helium nucleus. In the fusion reaction tremendous amount of heat energy is liberated. Similar reactions take place in the sun and other stars due to which, they have been producing continuously enormous amounts of heat and light energy. 

  

       The shell of the hydrogen bomb is made of a strong alloy. Two isotopes of hydrogen (deuterium and tritium) are kept inside this cover. One atom bomb is also enclosed in the same shell to initiate the fusion reaction. When the hydrogen bomb is to be exploded, the atom bomb is made to explode first. It produces a temperature of millions of degrees. At this temperature, deuterium and tritium combine together to form a helium nucleus and produce huge quantity of heat. This reaction is completed in one millionth of a second. In fusion, not only the helium nuclei are formed but neutrons are also produced. These neutrons carry out the fission reaction in uranium by which heat is continuously produced to carry out fusion reaction. That is why this bomb is more powerful. For peaceful uses, they can be modified so that the radio activity produced is minimal.

          So far hydrogen bombs have been developed by USA, Russia (former USSR), UK, France and China. Erstwhile USSR tested a hydrogen bomb in 1962 whose power was equivalent to 62 megaton TNT. 

How are valleys formed?

          The wide, broad plains or uneven tracts with gradual slopes between the mountains are called valleys. They are found in the mountains all over the world. Srinagar is one of the beautiful valleys in our country. Do you know how valleys are formed?

          Most of the valleys were formed by rivers. When streams originate on hill top, their water flows down the side of the hill. Because of the steepness of the slope, the river flows very fast and the force of water eats into the hillsides, forming a narrow V-shaped bed. With the passage of time, it becomes U-shaped when the water from other sides joins it and its breadth goes on increasing. Eventually the banks of the river become flat and the floor of the river widens. The area almost becomes like a plain. This is how a valley is formed. It takes thousands of years for its formation.

          Some valleys have been formed by glaciers. Glaciers are slow moving rivers of ice. The ice grinds deeply into the ground and at the same time smoothens out any ridges in its path. The glacier picks up all the rocks and other projections that come in its path, breaks them up and redeposits them smoothly over the ground. This makes the ground smooth and a U-shaped valley comes into existence.

          Sometimes the river changes its direction and thus the river bed becomes dry. The valley formed in this manner is called a dry valley.

          Sometimes when land sinks between two fractures in the earth’s crust, a valley is formed. These valleys are called ‘rift valleys’. The most famous valley of this type is the Great Rift Valley, which extends to more than 5000 km from Syria to East Africa. Narmada, a famous river of India, also flows through a rift valley.

          All the ancient civilizations started in the valleys only.

 

How are caves formed?

               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. 

How are Volcanoes formed?

            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.

 

What causes an Earthquake?

            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.

 

How are lakes formed?

           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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