With the aid of diagrams and examples, write explanatory notes on any two of the following:
(a) Rift valley (b) Horst (c) Volcanic mountain.
Explanation
(a) Rift Valley:
— tensional and compression forces operating; occurrence of two parallel faults.
— gravitational force leading to the sinking of the land between the faults.
— uplift of the side blocks where there are series of parallel faults the rift valley will be steeped
— steep sided.
— example East African rift valley, River Rhine rift valley or River Jordan Rift valley.
(b) Horst Mountain occurrence of two parallel faults;
— uplift of the land between the faults subsidence of the side blocks
— emergence of an upland
— steep sided
— the summit is almost equal
— sagging in the middle
— example: Ruwanzori mountain in East Africa
— may contain shallow lakes
(c) Volcanic Mountain;
— occurs in areas prone to volcanic eruption
— extrusive Vulcanicity
— magma pushed to the surface
— composed of mud ashes, bombs, cinders etc. solidifies to form a cone–shaped mountain
— may form crater lake
— Examples Mount Kilimanjaro, Ruwinzori, Vesuvius, Etna, etc.