How does the cooling rate of magma affect the formation of igneous rock?

Answer 1

by Jenny SMember since:October 28, 2008Total points:6,522 (Level 5)

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Best Answer - Chosen by VotersThe previous answers are correct, but there is an additional feature resulting from cooling rates.

A magma which cools rapidly will comprise small to microscopic crystals and generally be homogeneous.

A magma which chills slowly will not only form larger crystals, but may also have time to differentiate - that is for some of the earliest crystallised materials to settle through the magma chamber if there is an adequate density contrast between minerals. This results in different compositional rock types, layering within the body, and alignment of alongate crystals. Slower cooling magmas also have the possibility of forming late stage products such as aplitic and pegmatitic bodies. They also have time to alter themselves or the adjacent rocks by passing reactive fluids through themselves and the country rock.

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Answer 2

The rate of cooling affects the crystal size of the minerals in the igneous rocks. Slower cooling, larger crystals. Fast cooling, small crystals.

Answer 3

Igneous rocks form when hot magma cools inside or outside the earth. So, the cooling of magma affects them by creating them.