CHAPTER – III
THE EARTH MOVEMENTS
In the beginning there were
neither mountains nor oceans, plains or plateaus as familiar to us today. The powerful internal forces operating from
within the crust are called earth movements, both slow and sudden. They gave birth to all the physical relief
features on the earth. These forces are
of two types one, Endogenic and other Exogenic forces these two forces acted continuously
and created all the features of today.
Endogenic forces: The forces which are acting from inside the
earth are called Endogenic forces, which are of two types (i) Diastrophic and (ii)
catastrophic movements
Diastrophic movements: These are slow forces which act unnoticeably but
create most massive structures. These forces
act continuously and witnessed in the upliftment of plateaus or subsidence of
crust. These are of again two types (i)
Epierogenic forces and (ii) orogeny forces.
Epierogenic
forces are otherwise called as Radial forces as they act along the radius of the
earth, resulting in submergence and emergence of the crust. The continental shelf in the oceans is a
result of submergence of the continent and the emergence of the land from the
oceans results in the plateau formation eg Siberian plateau. India is a classical example for the emergence
and submergence, the west coast of India from south of Kathiawar up to Malabar
is a submergence coast. The features
like Dwaraka and Mahabaleshwaram proves the submergence. On the other hand the east coast from Malabar
till sundarbans represents the emergence, features like backwaters of Kerala, lagoons
best represents the emergence. Orogeny
forces, means the mountain building forces.
These forces act tangentially to the earth surface so called as
tangential forces. These are horizontal
forces and are of two types compression forces and tensional forces. Compression forces results in creating Fold Mountains,
when two forces are operating toward a centre compression can result forming
fold mountains and block mountains example the formation of Alps,
Himalayas. Tensional forces are the
forces which are acting away from the centre they result in Faulting &
Rifting. Rhine valley in Germany and Vosges mountains are the best examples.
Catastrophic forces: Unlike the Diastrophic movements these
Catastrophic movements are sudden the best examples are Volcanism and
Earthquakes.
