Our Changing Earth

The movement of the plates under the surface of the earth is caused due to different forces. Based on the kind of force, these are categorized into exogenic and endogenic forces.

1) The forces that act in the interiors of the earth are called the endogenic forces. The sudden endogenic forces result in the natural disasters such as volcano, earthquake, and landslides. They also cause the formation of mountains.

2) The forces that act on the exterior or surface of the earth are called exogenic forces. These forces cause erosional and depositional in nature. They result in the in the formation of rivers, occurrence of rivers and glaciers.

The core of the earth is made of molten magma. This molten magma keeps moving deep below the surface of the earth. Due to the movement of this magma, sometimes the lithospheric plates above it also moves. These movements of the plates are often responsible for earthquakes that result in the destruction of life and property on the surface of the earth.

Erosion is a process due to which the landscapes and other landforms wear away. Erosion may take place by a number of factors such as wind, sea waves, rivers and ice. These factors are also called the agents of erosion.

Sometimes, due to heavy rains or increases water levels, a river overflows its banks. This leads to the flooding of the neighbouring areas. As a result of these floods, layers of fine soil and other material called sediments gets deposited along its banks. This leads to the formation of a flat fertile floodplain. The raised banks are called levees.

As wind blows it carries sand other dust particles along it. As the speed of the wind slows down the sand and dust particles settle on the surface of the earth and forms pile. This phenomenon is responsible for the formation of sand dunes. Sand dunes are formed mostly in desert areas where sand is found is found in abundance. When wind blows in these areas, it lifts and transports sand from one place to another. When the wind stops blowing or reduces its speed, the heavier sand particles fall and get deposited in low hill-like structures. These are called the sand dunes.

The erosional and depositional activities of the sea waves leads to the formation of beaches. As water flows, it carried sediments along with it to the shore. Over a period of time, layers of sediments get deposited one over the other along the shore and forms flat-like landforms called the sea beaches. These are often flat and receives the sea waves that bring another layer of sand with them.

As a river enters and flows through the plains, it bens along its way and forms meanders. Due to continuous erosion and deposition, the meanders come closer and closer and detaches itself from the river. This forms a crescent-shaped lake called the ox-bow lake. It resembles the shape of a bow hence is named like ox-bow lake.

It is the depositional feature of sea waves

Flood plains and beaches the features of rivers and sea waves respectively.

Volcano is caused due to sudden movement of the interiors of the earth which causes a vent on the surface of the earth.

As strong winds blow in the deserts, they erode the rocks present in these areas. They erode the sides of the rocks, they blow giving the rock shape like a mushroom.

Ox-bow lakes are formed by the rives that divides into smaller meanders. These meanders separate from the river and form ox-bow lakes.

(i) Glacier (c) River of ice

Glaciers are called the rivers of ice as they a look like rivers that are made of ice.

(ii) Meanders (d) Rivers

The twisting of rivers, in the plain, leads to the formation of meanders.

(iii) Beach (a) Sea shore

Sea waves hit the sea shores to form beaches.

(iv) Sand dunes (h) Deserts

In deserts, the blowing winds lead to the formation of sand dunes.

(v) Waterfall (g) Hard bed rock

When the river tumbles at steep angle over very hard rocks, it forms a waterfall.

(vi) Earthquake (e) Vibrations of the earth

The sudden vibration of the surface of the earth is called earthquake.

Mushroom rocks resemble the shape of mushroom it means that they are narrower at the base and broader or wider at the top. These are mostly found in the desert areas, that are formed when the winds erode the lower part of the big rocks as they blow and the upper part remains wider.

Flood plains are formed due to overflowing of the rivers. The flood plains are made of the deposits that are carried by the rivers such as fine soil and sediments. These are rich in nutrients and are also suitable for growth of the plants. This is why they are very fertile and suitable for plant growth.

Stacks are a type of coastal landforms. These are formed as a result of the erosional activity of the sea waves. As sea waves strike the rocks continuously, it leads to the formation of cracks in them. Over time, these cracks become larger and wider and appear like caves. They are called sea caves. As these cavities become bigger and bigger only the roof of the caves remain, thus forming sea arches. Further, erosion breaks the roof and only walls are left. These wall like features are called stacks. Hence, the sea caves are turned into stacks over a long period of time.

As the lithospheric plates move they cause the vibration on the surface of the earth. These are called earthquakes. When the earthquakes are of a high intensity or are very strong, they cause damage to almost everything out of which the buildings are the most affected. Due to sudden and strong shaking of the ground, the high-rise buildings also shake and develop cracks in them. As a result they collapse.

1. Name of the feature: Waterfall

It is both erosional and depositional activity of the rivers. When the river tumbles at steep angle over very hard rocks or down a steep valley side it forms a waterfall.

2. Name of the feature: Meander

It is an erosional activity of the rivers. As a river enters and flows through the plains, it bens along its way and forms meanders.

3. Name of the feature: Flood plain

It is both erosional and depositional activity of a river. As it floods, the river water deposits layers of fine soil and other material called sediments along its banks. This leads to the formation of a flat fertile floodplain.