Earthquakes
There are many cause of earthquake like volcanic explosions, vibrations of crustal rocks and others. Read more on earthquakes.
Related
Gulf Stream
Dust Bowl region
Earth
Most Viewed in Geography
Continents
Protection of natural resources
Geography: information of Deserts
The rate of erosion depends largely upon the hardness of the rock. Devil's Tower, in Wyoming, is an example of a volcanic rock tower which once formed the core of a volcano and was left standing long after the softer surrounding rocks had been worn away.
Erosion
The surface of the Earth is constantly being worn away by natural forces such as running water, waves, ice, and the wind. This process is called erosion. It takes place slowly but surely.
In most regions, running water has the greatest erosive effect on a landscape. Water moving along a stream bed continually picks up and deposits rock fragments. The scraping action of these fragments deepens and enlarges the stream. The faster the flow, the greater is the action. A stream in flood can easily move massive boulders a great distance. Throughout the course of a river, particles are being worn away, transported, and deposited. The finer particles are transported to the lower reaches of the river, where they are deposited as silt.
On the coast, waves carrying sand and pebbles pound ceaselessly against the shore, cutting into and weakening the rock. In dry regions, the wind picks up particles of dust and sand and hurls them against the rocks. This natural 'sandblasting' gradually breaks down the rock into sand and dust.
In many mountainous regions the higher ground is snow-covered all the year round. As more snow falls, the snow underneath changes to ice. Vast 'rivers of ice', or glaciers, form in the valleys and gradually 'flow' downwards. As they move down, they break off and collect rock fragments which grind away other rocks.
However, erosion is not just something for the geologist to worry about. Farmers worry about it too, because fertile top-soil can be washed or blown away. To prevent this happening, farmers plow hilly land with furrows across the slope instead of up and down. This is called contour plowing. They also plant trees and grass to break the force of the falling rain and to bind the soil against wind erosion.
