Social Science [2 Marks Each] QUE-ANS

When the water of a riverfalls on solid rocks in its course in a steep sided valley or dashes on the low-lying land forcefully it is called a waterfall. If the height and the intensity of the speed of the waterfalls are less, these are known as 'rapids'.

The circular movement of a tectonic (lithospheric) plate changes the surface of the earth. The force which is originated in the interior of the earth due to the movement of the tectonic (lithospheric) plates is called 'Endogenic force'.

The molten magma deep inside the earth is solidified and the rocks thus formed are called 'Intrusive igneous rocks'. Due to the heat in the interior of the earth, the process of condensation (cooling down) of the magma is slower. That is why the Crystals in the rocks are larger. Granite is this type of rock.

Through a vent or a fissure on the surface of the earth, the hot lava, hot gases, rock fragments, ash, water vapour, etc. from interior of the earth erupt on the surface with great speed. This process or the phenomena is called volcanic eruption'.

Two natural disasters like earthquake and volcano take place due to the sudden movements of the earth.

The circular movements of the plates cause changes on the surface of the earth. The force which creates circular movements of these plates and which is created on the surface of the earth is called 'Exogenic force'.