Social Science VSQ (2 Marks)

During earthquakes, vibrations travel outwards from the epicentre as waves and propagate through the surface of the earth which produce sudden movements that leads to the collapse of buildings.

When cavities in sea caves become bigger and bigger only the roof of the caves remain forming sea arches. Further, erosion breaks the roof and only walls are left which forms the stacks.

Flood plains are very fertile because floods deposit layers of fine soil and other material called sediments which is ideal for cultivation along its banks.

In desert, wind is an active agent for erosion which erode the lower section of the rock more than the upper part. Therefore, some rocks have a shape of a mushroom having narrower base and wider top.

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

The forces that work on the surface of the earth are called as exogenic forces. The forces which act in the interior of the earth are called as endogenic forces.

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.

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'.

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.

A volcano is a vent or opening in the earth's crust through which molten material erupts suddenly.

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 material carried by the glacier such as rocks big and small, sand and silt gets deposited. These deposits form glacial moraines.

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.

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 earth's crust consists of several large and some small, rigid, irregularly- shaped plates, Le., slabs which many continents and the ocean floor.

There are three types of earthquake waves:

1. P waves or longitudinal waves.
2. S waves or transverse waves.
3. L waves or surface waves.

The landscapes are being continuously worn away by two processes:-

1. Weathering:- It is the breaking up of the rocks on the earth’s surface.
2. Erosion:- It is the wearing away of the landscape by different agents like water, wind and ice.

• Earthquakes cannot be predicted.
• Their impact can certainly be minimised if we are prepared before hand.

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.

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.

The process of erosion and deposition create different landforms on the surface of the earth.

The lithospheric plates move slowly because of the slow movement of molten magma inside the earth in a circular manner.

The highest waterfall is Angel Falls of Venezuela in South America. The other waterfalls are Niagara Falls located on the border between Canada and USA in North America and Victoria Falls on the borders of Zambia and Zimbabwe in Africa.

When the rivers tumble at steep angle over the hard rocks of a deep steep valley it forms a waterfall.
For example: Victoria waterfalls or Niagara waterfall.

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.

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