Our Changing Earth

The solid crust of the rocks forming the surface of the earth is known as Lithosphere .The lithosphere is broken into a number of plates. These plates are known as lithospheric plates.

Vertical earth movement and horizontal earth movement are the two kinds of tectonic movement.

A volcano is an opening in the earth’s crust which allows hot molten rock, ash and gases to escape from below the surface.

Volcanoes are generally found where tectonic plates are pulled apart or come together. Volcanoes can also form where there is stretching and thinning of earth’s crust, such as in the (African) rift valley.

When the lithosphere plates moves, the surface of the earth vibrates. The vibration can travel all around the earth. These vibrations are called earth quake.

Weathering is the process by which a bed rock may creemble or decay, because of the action of atmospheric moisture, rain, frost, temperature changes, chemical action or underlying water and other associated features.

The running water in the river erodes the landscape. When the river tumbles at steep angle over very hard rocks or down a steep valley side it forms a waterfall.

As the river enter the plains it twists and turns forming large bends known as meanders. Due to continuous erosion and deposition along the side of the meander, the ends of the meander loop come closer and closer.

An active agent of erosion and deposition in the deserts is wind. In desert we can see rocks in the shape of mushroom, commonly called mushroom rocks. The wind erodes the lower section of the rock more than the upper part.

When the grains of sand are very fine and light, the wind can carry it over very long distance. When such sand is deposited in large areas, it is termed as loess.

The river becomes so slow that it begins to deposit its load. Each distributary forms its own mouth. The collection of sediments from all the mouth forms a delta.

The erosion and deposition of the sea waves gives rise to coastal landforms. The sea wave deposit sediments along the shores forming beaches.