There are three types of rocks on Earth. Each rock type forms in a different way. Igneous rocks were the first rocks on Earth. They form from molten rock. Molten rock is rock that has turned to liquid because of extreme heat. Lava is the name for the molten rock that erupts from volcanoes. When molten rock is below the Earth’s surface, it’s called magma. When molten rock—either lava or magma—cools, it hardens into a solid. This forms igneous rocks. Some examples of igneous rocks are granite, obsidian and basalt. Much of Hawaii’s coast is covered in basalt. Waves break the basalt down over time, creating the black sand of some Hawaiian beaches.

Which of the following is true about lava and magma?

A. Lava and magma are both types of molten rock.
B. Magma uses waves to break down lava over time.
C. When magma cools and hardens it becomes lava.
D. Magma is called lava when it’s below the Earth’s surface.