A certain igneous rock has large grains. How do the large grains relate to subsurface (below-ground) events?

1 Answer
David Drayer
Jan 9, 2017

The slower the igneous rocks form the larger the crystals that are formed. The igneous rocks that form on or near the surface cool quickly with small crystals.

Explanation:

Generally the granite that forms deep in the earth has large crystals. lava that reaches the surface and cools quickly has small crystals. Obsidian or volcanic glass cools so quickly that the crystals are so small that they can't be seen.

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