FORCES THAT AFFECT THE EARTH
A. INTERNAL FORCES
These are the forces that originate and operate in the interior of the Earth. They are also called endogenic forces.
These forces are the result of energy produced by internal heat, chemical reactions taking place within the earth, and the transfer of rock materials to the Earth’s surface.
They cause vertical and horizontal earth movements.
1. INTERNAL EARTH’S MOVEMENT (DIASTROPHISM)
Are movements of the solid parts of the Earth away from one another, towards each other as well as upward and downward the earth’s crust.
Earth movements are caused by the forces working from inside the earth. These forces are also called diastrophic forces.
Earth movements: are constructional forces responsible for building of different types of landforms such as fracture, bends, subsidence or warping the earth’s crust to create different features such as depressions and mountains.
Earth movement are also called Tectonic movement because they contribute in building relief features (landforms).
TECTONIC –is a Greek word (tekton) which means BUILD.
Diastrophism: refers to different movements that occur within the rocks of the Earth’s crust (within the solid part of the Earth called Lithosphere).
There are two types of Earth movements vertical or radial movements and horizontal or lateral movements.
The two movements exert great tensional and compressional forces which are the basis for analysing the resulting landforms.
Compressional and Tensional force
Compressional force: are those which cause crustal rocks to move towards each other. It produces reverse faults and folding.
Tensional force: are those that pull crustal rocks in the opposite direction causing the rocks to move apart and rocks between faults to subside. It produces normal faults.
CAUSES OF EARTH MOVEMENTS
1. Movement of magma;
When a line of weakness/fault is created in the Earth’s crust because of pressure (strain), magma moves through that line of weakness leading to movement of the crust either vertically or laterally.
2. Convectional currents in the mantle;
These are circular movements of magma. These currents move from inside the mantle, towards the upper surface of the mantle and then horizontally and finally vertically inwards.
As these currents move horizontally beneath the SIMA, they exert a frictional pull on the crustal rocks causing them to move horizontally.
3. Isostatic adjustment;
When the earth’s crust is disturbed, the molten material (magma) in the mantle tends to move so as to maintain a state of balance within the Earth’s crust. This causes both vertical and horizontal movement.
4. Gravitational force (pressure);
Gravitational force that tends to pull all objects to the Earth’s centre exerts pressure on the crustal rocks to fill up the cavities which have been left behind by escaping magma.
This movement which is both vertical and inwards, causes the surface of the Earth to form depressions.
5. Falling of the heavenly body; when a heavy heavenly body like a meteorite falls on the ground it causes the shaking movement of the Earth’s crust that results in the Earth tremor.
6. Artificial causes; heavy moving vessels like a train and heavily loaded trucks cause shaking movements of the Earth’s crust, sometimes leading to occurrence of mass movement like soil creep, landslide and rock fall.
A. INTERNAL FORCES
These are the forces that originate and operate in the interior of the Earth. They are also called endogenic forces.
These forces are the result of energy produced by internal heat, chemical reactions taking place within the earth, and the transfer of rock materials to the Earth’s surface.
They cause vertical and horizontal earth movements.
1. INTERNAL EARTH’S MOVEMENT (DIASTROPHISM)
Are movements of the solid parts of the Earth away from one another, towards each other as well as upward and downward the earth’s crust.
Earth movements are caused by the forces working from inside the earth. These forces are also called diastrophic forces.
Earth movements: are constructional forces responsible for building of different types of landforms such as fracture, bends, subsidence or warping the earth’s crust to create different features such as depressions and mountains.
Earth movement are also called Tectonic movement because they contribute in building relief features (landforms).
TECTONIC –is a Greek word (tekton) which means BUILD.
Diastrophism: refers to different movements that occur within the rocks of the Earth’s crust (within the solid part of the Earth called Lithosphere).
There are two types of Earth movements vertical or radial movements and horizontal or lateral movements.
The two movements exert great tensional and compressional forces which are the basis for analysing the resulting landforms.
Compressional and Tensional force
Compressional force: are those which cause crustal rocks to move towards each other. It produces reverse faults and folding.
Tensional force: are those that pull crustal rocks in the opposite direction causing the rocks to move apart and rocks between faults to subside. It produces normal faults.
CAUSES OF EARTH MOVEMENTS
1. Movement of magma;
When a line of weakness/fault is created in the Earth’s crust because of pressure (strain), magma moves through that line of weakness leading to movement of the crust either vertically or laterally.
2. Convectional currents in the mantle;
These are circular movements of magma. These currents move from inside the mantle, towards the upper surface of the mantle and then horizontally and finally vertically inwards.
As these currents move horizontally beneath the SIMA, they exert a frictional pull on the crustal rocks causing them to move horizontally.
3. Isostatic adjustment;
When the earth’s crust is disturbed, the molten material (magma) in the mantle tends to move so as to maintain a state of balance within the Earth’s crust. This causes both vertical and horizontal movement.
4. Gravitational force (pressure);
Gravitational force that tends to pull all objects to the Earth’s centre exerts pressure on the crustal rocks to fill up the cavities which have been left behind by escaping magma.
This movement which is both vertical and inwards, causes the surface of the Earth to form depressions.
5. Falling of the heavenly body; when a heavy heavenly body like a meteorite falls on the ground it causes the shaking movement of the Earth’s crust that results in the Earth tremor.
6. Artificial causes; heavy moving vessels like a train and heavily loaded trucks cause shaking movements of the Earth’s crust, sometimes leading to occurrence of mass movement like soil creep, landslide and rock fall.