What's more interesting for you in this chapter?
1.
The lithosphere is broken into a number of plates known as the Lithospheric plates.
The forces which act in the interior of the earth are called as Endogenic forces and the forces that work on the surface of the earth are called as Exogenic forces.
Endogenic forces sometimes produce sudden movements and at the other times produce slow movements. Sudden movements like earthquakes and volcanoes cause mass destruction over the surface of the earth.
A volcano is a vent (opening) in the earth’s crust through which molten material erupts suddenly.
When the Lithospheric plates move, the surface of the earth vibrates. These vibrations are called earthquakes.
The place in the crust where the movement starts is called the focus.
The place on the surface above the focus is called the epicentre.
MAJOR LAND FORMS
Weathering is the breaking up of the rocks on the earth’s surface.
Erosion is the wearing away of the landscape by different agents like water, wind and ice.
The eroded material is carried away or transported by water, wind, etc. and eventually deposited. This process of erosion and deposition create different landforms on the surface of the earth.
Work of a River
When the river tumbles at steep angle over very hard rocks or down a steep valley side it forms a waterfall.
As the river enters the plain it twists and turns forming large bends known as meanders.
Due to continuous erosion and deposition, the ends of the meander loop come closer and closer. In due course of time the meander loop cuts off from the river and forms a cut-off lake, also called an ox-bow lake.
Floods deposits layers of fine soil and other material called sediments along its banks. This leads to the formation of a flat fertile floodplain.
The raised banks are called levees.
The break up of a river into a number of streams which are called distributaries.
Each distributary forms its own mouth. The collection of sediments from all the mouths forms a delta.
The hollow like caves formed on the rocks by the striking of waves are called sea caves.
As these cavities become bigger and bigger only the roof of the caves remain, thus forming sea arches.
The steep rocky coast rising almost vertically above sea water is called sea cliff.
Work of Ice
Glaciers are “rivers of ice” which too erode the landscape by bulldozing soil and stones to expose the solid rock below.
The material carried by the glacier such as rocks big and small, sand and silt gets deposited. These deposits form glacial moraines.
Work of wind
An active agent of erosion and deposition in the deserts is wind.
In deserts, rocks in the shape of a mushroom are called mushroom rocks.
Winds erode the lower section of the rock more than the upper part.
When wind stops blowing the sand falls and gets deposited in low hill – like structures. These are called sand dunes.
When the grains of sand are very fine and light, the wind can carry it over very long distances. When such sand is deposited in large areas, it is called loess.
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