MODE OF FORMATION
Block mountain are formed when the earth cracks due to faulting. Faulting may result from tension forces or compression forces. Tensional forces are those that tend to pull the earth crust apart and they result in a normal fault while compressional force is those that shorten the crust to produce a reserve or thrust fault.
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Therefore if a block of rock between two normal fault rises or the land on either side of the block subsides a block mountain or horst is formed.
At times a block in between two faults may subside so that rift valley or graben is formed. The slope and height of block mountain are modified by an agent of denudation.
Characteristic of the rift valley:-
- These are a tough between two parallel faults
- It has steep-sided walls
- It also has flat bud, at the time, irregular floor
- Rift valleys are usually very deep
An example is the Rhine valley, Dead Sea, Jordan Valley, Great East African Rift valley which is about 4,800km. It should be noted that landforms produced by faulting are rift valley and block mountain.
MODES OF FORMATION
Rift valley occurs when there are tensional and compression forces operating. Two parallel faults occur and there will be gravitational force leading to the sinking of the land between the fault. The side blocks will be uplifted. The rift valley will be steeped where there is a sense of parallel fault.
VOLCANIC MOUNTAINS
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Characteristic:- Volcanic mountain is made up of lava. They have irregular sides with a conical shape. Materials that make up volcanic mountain include ash, volcanic bombs, cinders e.t.c which are arranged in layers.
MODE OF FORMATION:- Volcanic mountain are formed from volcanoes which are built from material ejected through fissures or vent in the earth crust. The materials include molten lava, volcanic bombs, cinder, ash and liquid mud.