It expects students to give detailed account of how the endogenous factors lead to formation of volcanoes with suitable examples.
Introduction:
The horizontal and vertical movements caused by the forces coming from the origin of the earth is known as endogenic forces. The origin of endogenic force is caused by the contraction and expansion of rocks due to variation in thermal conditions and temperature inside the earth. These forces are responsible for creation of many landforms one of such landform is volcano.
Body:
Endogenic factors that lead to formation of volcanoes:
The ultimate source of energy behind forces that drive endogenic movements is earth’s internal heat.
Endogenic movements are divided into diastrophic movements and sudden movements.
Plate Tectonics: The majority of volcanoes occur where two lithospheric plates converge and one overrides the other, forcing it down into the mantle to be reabsorbed.
Ocean floor spreading: A major site of active volcanism is along the axis of the oceanic ridge system, where the plates move apart on both sides of the ridge and magma wells up from the mantle.
Weak Earth Surface: Because of high pressure in the earth’s interior, the magma and gases escape with great velocity as the pressure is released through eruptions where opportunity is provided by weak zones along the earth’s surface.
Faults: Whenever extreme pressure builds in the mantle, along fault lines an eruption is likely to happen next. The earthquakes, for instance, may expose fault zones through which magma may escape and volcanoes can be formed.
Magma crystallization: Decreasing temperatures can cause old magma to crystallize and sink to the bottom of the chamber and this movement can force fresh liquid magma up and out – similar to dropping a brick in a bucket of water.
Plate movement: Volcanism may occur because of plate movement over a “hot spot” from which magmas can penetrate to the surface. e.g. Islands of Hawaii
Conclusion:
Through these endogenic factors volcano formation takes place. Depending on the level of activity volcanoes are further classified as Active, Dormant and extinct. Apart from playing a prominent role by giving cooling effect to most part of earth, volcanoes also contribute Ash and lava which breaks down to form soil and rocks.
