Translations of Encyclopedia about Geology

Rocks, Mountains, aand Valleys

The earth's surface is the result of a combination of many different changes. Forces causing these changes on the earth's surface are at work both on the exterior as well as the interior of the earth.

Convective flow, movement of the plates, volcanoes, earthquakes are some of the interior forces. Water in the lakes, rivers, aand oceans, wind, aand moving ice are the exterior forces.

All these forces leave visible marks all over the surface of the earth aand are the cause of important changes. Mountain ranges form when layers of rock fold as a consequence of a tectonic plates collision.

Mountain ranges quite clearly differ from their lower-situated surroundings by their foothills. In accordance with the height aand shape, we distinguish between highlaands, where the difference between the summit aand the foot is between 500 aand 1000 metres aand their shape is generally rounded, aand high mountain ranges, where the difference of altitude is over 1000 metres. High mountains are often steep aand jagged, aand in many cases they reflect the changes wrought by glaciers.

From the geological point of view, we classify mountain ranges into volcanic, aand in accordance with the type of formation, into fault-block fold, aand fault-fold mountains. Residual mountains remain while minerals in the surrounding rocks are being eroded, aand then they are carried away by wind or water.

Similar formations are the rocks in the shape of a mushroom, occurring in the desert. Winds close to the surface blow sharp particles of saand against its lower part, leaving it in the end staanding on a sort of thin stem. The saand may be deposited in the form of dunes. Dunes are subjected to constant changes as well, because the laandscape lacks protective vegetation aand the impact of the wind is especially intense.

Caves form when water containing acids flows through limestone aand dissolves it. When such a cave collapses, it may create large ravines. We often find on the earth's surface long cavities between jutting rocks. They were formed by flowing water or moving glacier.

However, all forms of the earth's surface are subjected in particular to weathering aand erosion. How much these forces will affect everything depends on the climate, type of rock, aand the degree of chemical decomposition.

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