What causes lava to form?
The seething rivers that flow from Hawaii’s erupting volcanoes are made of molten minerals. The temperatures that liquefy these lavas must be very high for they contain such rocky minerals as silica and basalt. The volcanoes must provide as much heat as blast furnaces. Rivers and floods of flowing lava may spread over the surface or ooze between layers of rock far below the surface. Earth scientists suspect that they spring from reservoirs of molten magma that form at the deep roots of volcanoes. But these experts are not so certain what causes these pools of buried magma. We know a lot about the structure of our planet, but not enough to explain everything that goes on deep below the surface. Vibrations of Earthquakes indicate that its materials are arranged in layers that become denser toward the center. Other evidence suggests that the materials become hotter as we go down. This seems logical since the lower levels are under pressure from those above, and pressure tends to generate
