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Mountain Features

 
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A mention of Mountains, and we immediately think of snow covered sprawling ranges, picturesque valleys, deep gorges, spectacular waterfalls and meandering rivers.

A mountain is a landform that rises much much higher than the surrounding terrain. It is generally higher and steeper than a hill, but there is considerable overlap. One point of difference between the two is that the mountain top, known as a summit or peak has a much smaller area than its base. A series of mountains form a mountain range. Himalaya is a mountain range. It runs for about 2400 km, and its width varies between 250-300 km. All of the highest mountains can be found here. The average height of the Himalaya is about 5 km.

A mountain range consists of peaks and valleys. The bases of two or more peaks form a valley. Valleys can be narrow or broad. If a river flows through the valley then it is called a river valley.

When one climbs a mountain, the higher one goes, the colder it gets. The average temperature falls by about 1.7 degree Celsius for every 300 meter of altitude. The average temperature will be close to 0 degree Celsius on mountains above 5000 m. Such mountains are snow covered. Some mountains are permanently covered with snow. On some, the snow melts in summer, exposing the rocky face of the mountain. Where snow does not melt, huge snow fields and/or glaciers cover the more gradual slopes of mountains. Over many years snow gets compacted. Compacted snow is ice. Layers and layers of ice respond to various forces on the mountain side and may begin slipping (flowing down). Such large body of ice moving slowly down a slope is termed a glacier. A glacier has a snow field at its higher end. At the lower end of the glacier is its terminus. As a glacier flows (ever so slowly), it can develop deep crevasses. Seracs can also form. A serac is a block or sharp ridge of ice among the crevasses of a glacier.

Snow and frost help in weathering of rocks. Water seeps into fractures in rocks and expands when it freezes. It can then break off large pieces of rock. Rock begins to disintegrate when water and atmospheric gases react chemically with the minerals in the rock to form new minerals. Broken rock, big and small, tumbles down the mountain side. Glaciers also carry them in their flow. Moraines are rock debris that are carried by glaciers and finally deposited. When deposited at the glacier terminus, it is called terminal moraines.

When glaciers melt, the melted water flows from the terminus giving rise to a river or forming a lake. Glaciers are the sources of perennial rivers.

Lower mountains or mountain sides are not snow covered. However, the night temperature can fall below freezing point. Streams and rivulets freeze then. Ferocious winds and storms; rapid waters; avalanches and glaciers; land slips ... all these shape the mountain face. Mountains sides are constantly eroded by these weather elements.

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