Can you explain how the cooling rate of a magma may cause variation in the chemical composition of the rocks which are formed
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goldberg443
ANSWERS: 1
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rapid cooling gives a more homogenous mixture of small crystals of different rock types. Slow cooling allows rocks with lower melting points to crystallize last, so that each different rock has a chance to grow into large crystals. A good example is a geode. Expelled from an underwater vent the outside cools rapidly giving an amorphous structure of rock surrounding a liquid interior. The solid outer cases insulates the inner liquid from the cooling effect of the water so that it cools slowly, allowing relatively pure crystals to grow in layers. Since the outside is rigid and formed big enough to contain the hot interior, as the interior cools and solidifies it shrinks, often leaving an empty hole in the centre. The lowest melting components are often seen as crystals extending into and around this empty space. There is a process called zone refining in which a core of material can be heated in a slowly moving furnace. The lowest melting components will tend to move with the furnace and can be separated out at the end of the core.
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