Lava Lava Lava is molten rock generated by geothermal energy and expelled through fractures in planetary crust or in an eruption, usually at temperatures from . The structures resulting from subsequent solidification and cooling are also sometimes described as "lava". The molten rock is formed in the interior of some planets, including Earth, and some of their satellites, though such material located below the crust is referred to by other terms. A lava flow is a moving outpouring of lava created during a non-explosive effusive eruption. When it has stopped moving, lava solidifies to form igneous rock. The term "lava flow"
Volcanism rapidly it cools. Magma that reaches the surface to become lava cools rapidly, resulting in rocks with small crystals such as basalt. Some of this magma may cool extremely rapidly and will form volcanic glass (rocks without crystals) such as obsidian. Magma trapped below ground in thin intrusions cools more slowly than exposed magma and produces rocks with medium-sized crystals. Magma that remains trapped in large quantities below ground cools most slowly resulting in rocks with larger crystals, such as granite and gabbro. Existing rocks that come into contact with magma may be melted and assimilated into the magma. Other