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Mountains, information about mountains

Mountains cover vast areas of the Earth's surface. The Rockies of North America, the Andes of South America, the Alps in southern Europe, and the Himalayas in Asia are among the largest and most spectacular of the world's mountain ranges. The Himalayas are the most magnificent of all. There lie many of the world's highest peaks including Everest (over 29,000 feet). Because of its height, the Himalaya range is often referred to as 'the roof of the world'.

Mountainous regions are often breathtakingly beautiful, with snowcapped peaks, ice-blue lakes, and cascading waterfalls. But they can also be extremely dangerous. Rock falls, avalanches, and treacherous weather conditions can turn even a simple mountain walk into a desperate fight for survival.

Mountains, information about mountains
An example of North America's fine mountain scenery is this view of Mount Hood, an inactive volcano in the Cascade Range, North Oregon	The most recent mountain system to be built stretches from western Europe to the Java Sea in Asia. It includes the European Alps

Mountains are a feature not only of the land, but also of the oceans. Sometimes these submarine mountains reach the surface of the ocean and form islands. The Bermuda Islands and the Azores are examples of this. The ocean bed, like the land, is criss-crossed with mountain ranges, plains, and deep valleys.

Mountains are formed as a result of movements in the Earth's crust. The devastating earthquakes that often occur in Persia, South America, Japan, and other regions provide us with a constant reminder of the fantastically powerful forces at work inside the Earth.

Mountains, information about mountains
The first stage of the mountain building cycle. Sediments accumulate in the sinking trough	The trough fills at the expense of the rising land surrounding it
Stage three. The trough has been compressed, so that at the end of the second stage the sediments are buckled up and folded over the edges of the trough. The mountains gradually rise to regain balance	Mountain ranges and lowland plains behave in the same way as large and small icebergs, and tend to 'float' on the denser material below

These earth movements give rise to three basic kinds of mountains - fold, block, and volcanic. Fold mountains form when two ancient land masses move towards each other and compress the land in between. The compression forces the land into great, wave-length folds. The Swiss Alps in Europe are examples of fairly young folds (about 15 million years old). The highlands of Britain are examples of old folds (about 240 million years old).

Sometimes earth movements may produce lines of weakness in the Earth's crust called faults. As the movements continue, great, block-like masses of the crust move along the line of the faults. They may subside below or be raised above the general land level to form block mountains, such as the Sierra Nevada in the United States. Long, deep valleys formed by land subsiding between parallel faults are called rift valleys. The best-known example of a rift valley is in East Africa and includes the Red Sea.

Proceeding from the scientific information, volcanic mountains are heaps of volcanic ash and lava. Their growth is often very fast. In 1943, a Mexican farmer found a small hole in his field. Smoke coming out of the hole brought ash which covered his crops. Soon a volcanic cone began to form and lava started to flow from the hole. In 1952, volcanic activity ceased and the volcano, called Paricutin, stood 1,345 feet high.

From the day they are formed, mountains are subjected to the continuous action of the weather. The rain beats down, the sun scorches, and the frost freezes and shatters. Even the hardest rock becomes worn away in time. Rivers flow through and deepen the valleys. At high altitudes frozen 'rivers' of ice called glaciers form. They grind their way downwards widening and scarring the valleys.

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