Distinguish between endogenetic and exogenetic forces.
Answers
ENDOGENETIC FORCES
They originate in the interior of earth.
Cause sudden (through earthquake and volcanoes) or slow movements.
The energy for these forces is generated by radioactivity, rotational and tidal friction and primordial heat.
Endogenic forces can further be divided into two parts:-
Diastrophism:- It includes slow bending, folding, warping and faulting of earth crust. Orogenic movements (mountain building forces) and Epeirogenic movements (continents building forces) are two main forms of diastrophism. These forces work very slow and their work is almost imperceptible.
Sudden Movements:- These movements cause considerable deformation of earth’s crust over a very short span of time. These are of two types- Earthquake and Volcanoes.
Examples- Mountain building such as Himalayas, Rockies and Andes; African Rift Valley due to Faulting.
EXOGENIC FORCE
They occur on the earth’s surface.
They work to wear down the reliefs and elevations (degrade) and fill up (agrade) the depressions on the earth surface.
All the exogenic processes can generally be called as Denudation which means strip off or uncover.
Denudation includes weathering, mass wasting, erosion and transportation.
These forces are a direct result of stress induced in earth materials due to various forces which occur due to sun’s heat.
Main forces involved are:-Gravitational forces, molecular stress, chemical actions, and kinetic energy.
Effects of most of the exogenic forces are slow but in a long run they affect the rocks drastically through wearing the rocks down and accumulating the weathered or eroded material to create new landforms.
Examples- Formation of river valleys, springs, deltas, sand dunes, beaches etc.