Earth Movements


The forces working from inside the earth in turn cause movements in its crust. These movements are called earth movements.

Since, these movements pertain to or rise from, the movements of the actual structure of the earth’s crust; they are also called tectonic movements.

These are the earth movements which are constructional and have been responsible for buildings of different types of land forms.

 

The physiography of India was entirely different about 60 million years ago.

The vast Tethys Sea existed in that area where the Himalayan ranges and Indo-Gangetic plain exist.

The Tethys Sea was gradually filled up by the sediments brought by rivers from the surrounding regions.

Later, the sedimentary rocks formed in the beds of this sea gradually emerged in the form of the Himalayas in the north and Indo-Gangetic plain to its south.

The Malwa plateau and Deccan traps of India, Columbia and Snake Rivers Plateau of North America, Kimberlay Plateau of Australia and Parana and Patagonian Plateaus of South America were also formed by the solidification of molten lava which had escaped from the earth’s interior to its surface at different geological times.

The evidence shows that the surface of our earth never remained the same as it is today and neither it will be the same in the future.

The earth movements are classified on various basis. On the basis of time taken by such movements, they are divided into:

[1] Slow movement

[2] Sudden movement

 

[1] Slow Movement

The movements which bring about changes on the Earth’s crust very gradually or slowly taking hundreds or thousands of years are called slow movements.

These movements act on the earth’s crust either vertically or horizontally.

Acting vertically, they cause uplift or subsidence of a part of the crust.

The raised sea-beaches along the Kathiawar coast of India which contain the shells of marine life clearly point out that this coast was once below the sea level.

Similar raised beaches are found In Orissa, Andhra Pradesh, and Tamil Nadu along the eastern coast of India as well.

These beaches have been uplifted to a height ranging between 15 to 30 meters above the mean sea level.

On the other hand, there are numerous examples of submergence.

Such as the presence of peat and lignite beds found below the sea-level in Sunderban Delta, the submerged forest in Tirunelveli in Tamil Nadu and the submerged forest on the east coast of Bombay Island.

 

[2] Sudden Movements

The examples of such movements are volcanic eruptions and earthquakes.

The changes brought about by these two events are so sudden that the courses of rivers undergo a change, and the lava flow results in the formation of mountains, uplands, and plateaus in a matter of days.

Landslides occur in mountainous regions due to these movements.

Vertical and horizontal movements of the earth