Discuss each of the following (i) factors controlling the cooling rate of magma and its effect on rocks (ii) The effect of structure and texture of magmatic rocks.
QUESTION 1
Discuss each of the following
(i) factors controlling the cooling rate of magma and its effect on rocks
(ii) The effect of structure and texture of magmatic rocks.
(i)Magma- Magma is the molten or semi-molten natural material from which all igneous rocks are formed. Magma is found beneath the surface of the Earth.
Cooling of magma -As a magma begins cooling inside the earth, high-temperature minerals are the first to form crystals. These solid crystals float within the remaining molten rock. This partially crystallized / partially molten magma is then extruded, so that it cools very rapidly.
Factors controlling the Cooling rate of magma-The depth of the intrusion, the shape and size of a magma body: the greater the surface area for a given volume of intrusion, the faster it cools, and the presence of circulating ground water: water passing through magma absorbs and carries away heat.
Effect of Cooling rate of magma on rocks- The factor that affects the size of the crystals and the texture of the rock is the cooling rate of the molten rock or magma. If the magma cools rapidly, the crystal formed is very small. This rock has a fine-grained texture. On the other hand, if the magma cools slowly, the crystal formed is large.
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