When magma rises up to the surface of the Earth from a volcanic eruption or through vents, it turns into lava. When this lava stops flowing and cools, it hardens into what is known as igneous rock.
Magma is a molten liquid rock that is located under the surface of the Earth and contains dissolved gases, rock fragments and crystals. The liquid portion of magma is called melt. When magma rises through the cracks in the seafloor, it hardens into a crust. The Pacific Ocean and Hawaiian Islands were formed from underwater volcanic eruptions where the lava hardened and built up an island chain.