What Causes the solidification of molten rock?

Answer 1

As magma rises to the surface and becomes lava, the lava cools and hardens to form igneous rock.

Answer 2

The solidification of molten rock is caused by cooling of the magma as it loses heat energy to its surroundings. As the temperature decreases, the atoms and molecules in the magma slow down and arrange themselves into a solid crystal structure, forming igneous rocks. Rapid cooling results in fine-grained rocks, while slow cooling leads to coarse-grained rocks.