Earth Contraction - Earth Contraction
Earth Contraction (1) Add new question
Question
Q: what do you know about the contraction of the earth?
| Option | Answer | Is Correct |
|---|---|---|
| 1 | The interior of the earth is very hot and is gradually cooling. As it cools, it contracts and occupies less space. This causes wrinkles or folds on the crust of the earth. Consequently some portions of its surface rise and some sink slowly. The elevated portions make mountains and plateaus, while the sunk portions became valleys and seas or oceans. In case the rocks are too hard loo fold on cooling, they break forming earth (technically called as faults). Earthquakes, An earthquake is a sudden, violent shaking of a part of the earth. Quake means to shake, to shudder, to tremble for want of firmness. Many towns are destroyed and there occurs a considerable loss of life and property. Some places are submerged under the sea. Big cracks and fissures are formed on the surface of the earth which interrupt communication. Sometimes rivers disappear or change their courses. At the same time they may be useful to man to a certain extent. Precious matter and minerals may crop up to the surface, new springs may be formed, and new lands for habitation may appear above the surface of the sea. How is an earthquake caused? There are various causes. A dormant volcano (a volcano which suddenly rises into activity after having remained inactive for years), when it rises into activity or an active volcano when it discharges matter with greater violence, shakes the surrounding area. Sometimes water percolates deep down into the earth and turn into steam on account of the internal heat. The stem on expanding tries to force its way out and causes an earthquake. When the interior of the earth cools and contracts, the outer crust in some places cracks, or some part of it actually drops down, This also causes an earthquake. | |
| 2 | Temperature also plays a great part in bringing a best changes on the surface of the earth. During the day the rocks are heated, and they expand. At night they get cool. By alternate expansion and contraction the rocks break up. In deserts and dry regions this action is very conspicuous on account of the extremes of temperature. Thus rocks are broken up into sand. Glaciers are slow-moving bodies of ice. When snow falls on high mountains it hardens into ice. In the cooling of time huge mass of ice is formed and it begins to slow down the mountain slope. These sliding masses are called Glaciers. They move very slowly, some of them move only a few inches or feet in a year. As they slide down a contain slope they scoop out valleys and bring with them stones, etc. On reaching warm regions they melt and leave down the stones brought with them. After melting they form rivers or lakes. | |
| 3 | Volcanoes are mountains which has been formed conical in shape by the accumulation of layers of lava. The interior of the earth is hot enough even to melt the hardest rocks. The hot matter, that is, lava, etc.. in the interior of the earth is pressed dawn by the pressure of the crust. Whenever it finds a weak spot in the crust it gushes out through a crack or a hole and accumulates round it. Sometimes rain water or sea water percolates into the soil and sinks deep down into earth. There it is convened into steam by the internal heat and forces its way out of the crust bringing with it large quantities of ashes, lava, etc. Gradually, in the course of thousands of years, this mass of lava grows big enough to be called a mountain. This lava forms a plateau when it spreads over the surface. |
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