Question

How does the rate of cooling affect the size of the mineral grains in igneous rocks?

a) It makes them larger.
b) It makes them smaller.
c) It has no effect on their size.
d) It causes the rocks to melt.

Answer 1

The rate of cooling affects the size of mineral grains in igneous rocks. Slow cooling rates result in larger mineral grains, while fast cooling rates produce smaller grains.

Step-by-step explanation:

The rate of cooling affects the size of mineral grains in igneous rocks. Slow cooling rates (thousands to millions of years) result in larger mineral grains, while fast cooling rates (days to hundreds of years) produce smaller grains. Igneous rocks with large grains are called intrusive or plutonic rocks, which cool slowly within the Earth. On the other hand, igneous rocks with tiny grains are called extrusive or volcanic rocks, which cool quickly on the Earth's surface.