ANSWER IN ONE SENTENCE
On what basis are the movements in the interior of the earth classified?
Answers
Answer:
The movement of these plates causes changes on the surface of the earth. The earth movements are divided on the basis of the forces which cause them. The forces which act in the interior of the earth are called as Endogenic forces and the forces that work on the surface of the earth are called as Exogenic forces
INTERNAL LAND FORMING/ENDOGENETIC PROCESSES
-Processes operating in the interior of the earth resulting in the formation of natural physical features or landforms.
They are caused by earth movements.
Examples of these processes are folding, faulting and Vulcanicity.
Formation of land forms by internal land forming processes is determined by:
Nature and age of earth materials
Type of movement involved
Intensity and scale of movement involved
Crustal Earth Movements
-Displacement of the earth’s crustal rocks.
They are brought about by tectonic forces which originate and operate in the interior of the earth e.g. tensional forces (which operate along horizontal plane moving away from each other), compressional forces (which operate along horizontal plane moving towards each other), shear forces (which move past each other with unequal strength) and gravitational forces (which attracts things to the earths centre).
Earth movements are of 2 types:
1. Horizontal/lateral/orogenic movements
2. Vertical/epeirogenic movements
Horizontal Earth Movements
-Movements which act along a horizontal plane within crustal rocks.
They are caused by tensional and compressional and shear forces.
Effects
They cause:
Strain and stretching of crustal rocks due to stretching caused by tensional forces which cause formation of cracks or faults.
Squeezing and shortening of crustal by compressional forces rocks which cause them which also cause formation of faults.
Crustal rocks to shear by slipping past each other or by dividing into layers which is caused by shear forces.
Results of Horizontal Earth Movements
-results in the formation of the following features:
1. Faults
2. Rift valleys
3. fold mountains
4. Escarpments
5. Basins
6. Tilt blocks
7. Block mountains
Vertical Earth Movements
-Movements which occur along the earth’s radius or towards the earth’s surface or towards its centre.
Effects
Causes:
Subsiding/sinking/downwarping or pulling of crustal rocks downwards.
Uplifting/upwarping or pushing of crustal rocks upwards
Tilting of crustal rocks or shearing in vertical direction due to grater uplift on one side.
Results of Vertical Earth Movements
1. Raised cliffs
2. Tilt blocks
3. Rift valleys
4. Fault scarps/escarpments
5. Plateaus
6. basins
Causes of Earth Movements
(a) Magma movement within the earths crust.
(b) Gravitational force
(c) Convectional currents in the mantle
(d) Isostatic adjustment
Magma Movement within the Earths Crust
When magma moves with force pushing crustal rocks horizontally or vertically.
When magma moves from reservoir and leaves empty spaces onto which crustal rocks are pulled inwards.
Gravitational Force
-When the attractive force of the earth pulls crustal rocks into empty spaces left after magma escaping from the reservoir.
Convectional Currents within Mantle
-When convectional currents in magma in mantle drug crustal rocks by friction.
Horizontal movement of currents cause horizontal movements while vertical cause vertical movements.
Isostatic Adjustment
-Rising of continental masses to restore the upset state of balance between sial and sima layers.
-Isostacy is the state of balance between sial and sima layers.
It can be disturbed by erosion on continents and melting of continental ice sheets.
The reduced weight causes continental masses to rise.
Theories Explaining the Earths Movements
A theory is reasoned ideas intended to explain facts or ideas.
There are 2 theories which explain the earth’s movements namely the Continental Drift Theory and the Plate tectonics theory.