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In this article, we would discuss the formation of landforms.
Volcanoes
1. Tremors or shaking of the earth’s crust is called an earthquake. Different parts that make the earth’s crust is known as plates. Movement of these plates cause an earthquake.
2. Ejection of lava through a vent or a fissure near or on the surface of the earth is known as a volcano.
3. Magma: Molten and semi-molten rock mixture deep inside the surface of the earth is known as magma. Magma is heavily charged with gases such as carbon- dioxide, sulphurated hydrogen and small proportions of nitrogen, chlorine and other volatile substances.
4. Lava: It is the mobile magma that absorbs various gases , dust, sand particles, water vapour and rock fragments. The gases contribute in increasing the mobility and explosiveness of the lavas. The lava is of two types: Basic and Acidic
5. Acidic lava: Highly viscous with a higher melting point, it is light in colour and has low density. It has a high percentage of silica and flows slowly. The resultant cone is therefore steep-sided. The rapid congealing of lava in the vent obstructs the flow of the out-pouring lava resulting in loud explosions (explosive ejection) throwing out many volcanic bombs or pyroclasts. If the lava is too viscous they form a spine or plug at the crater.
6. Basic lava: Less viscous with a very high temperature, basic lava is dark coloured like basalt, rich in iron and magnesium but poor in silica. They are not very explosive and flow quietly. Due to its high fluidity, they flow readily with a speed of 10 to 30 miles per hour. They spread as thin sheets over a large distance before solidifying. The resultant volcano is gently sloping with a wide diameter and forms a flattened shield or dome.
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