Earth relief – roughnesses of earth crust with various outlines and the sizes. It changes under influence of both external, and internal forces. Changes happen very slowly and imperceptibly, and first of all the relief is influenced by the processes happening in the depths of Earth and causing the movement of tectonic plates. To a lesser extent external forces – winds, space forces, human activity work.
Instruction
1. Several billions years ago on the surface of our planet there was no solid bark. The melted substances, metals, minerals and other breeds in the liquid state floated on deeper layer. Light substances rose up, heavy fell, there was a constant movement. Gradually breeds cooled down and hardened. Tectonic plates – blocks of earth crust which constantly moved relatively each other under the influence of thermal and gravitational currents to cloaks - the following layer of Earth were formed. In some places of a plate were rumpled, forming mountains and dents, in others dispersed, forming oceanic hollows. These movements caused earthquakes, volcanic eruptions and other processes which took part in formation of a relief too.
2. At the same time the Earth's surface was influenced also by other processes, including external: winds, falling of asteroids, current of water. Plates for all history of Earth constantly moved, changing outlines of continents and oceans. The current situation of earth's plates, borders of oceans and continents are unstable. They continue to change slowly but surely.
3. Under the influence of internal forces in some areas of Earth, earth crust was thickened and rumpled therefore mountains appeared. The young mountains which just appeared were affected by an erosion, aeration and destructions, slowly falling. Process of destruction of mountains lasted hundreds of millions years. So, the Ural Mountains are considered as one of the most ancient, they began to be formed 350 million years ago. The Himalayas, on the contrary, are young. In them mountain building processes are still not finished.
4. As mountains collapse, the relief becomes more and more flat, plains are formed. The mountain rivers cutting the Earth's surface gradually broaden the course, form wide valleys and begin to flow more and more slowly.
5. The cycles of an erosion of mountains were several times repeated on our planet: the relief towered, then collapsed, then on this place new mountains rose again. While the internal processes happening in the depths of Earth force earth crust to be rumpled and form new forms of a relief, external forces destroy them. Vveter and water act not so quickly, but is persistent and productive, leaving behind flat plains. Each site of the earth's surface has the history, and so far the person cannot precisely tell how there was a formation of the Earth's surface in any given place. The science geomorphology is engaged in studying development of a relief.