Lava is made of crystals, volcanic glass and volcanic gases. Lave erupts when bubbles of volcanic gases are formed by the cooling of molten rock - also known as magma - beneath the Earth's surface.
The chemical composition of lava includes elements such as oxygen, aluminum, iron and magnesium. It erupts as a mixture of crystals, liquid and bubbles, and eventually hardens into volcanic glass. Volcanology, or the study of volcanoes, is critical to predicting volcanic eruptions in areas such as Alaska and the Hawaiian Islands. Volcano research is also used in the understanding of other sciences, such as geology, petrology and geophysics.