lava, magma (molten rock) emerging as a liquid onto Earth's surface.

lava, magma (molten rock) emerging as a liquid onto Earth's surface. The term lava is also used for the solidified rock formed by the cooling of a molten lava flow. The temperatures of molten lava range from about 700 to 1,200 °C (1,300 to 2,200 °F). ... The higher the lava's silica content, the higher its viscosity.