Lava flow

Aerial view of a channelized `a`a flow on Mauna Loa Volcano, Hawai`i.

Lava flows are masses of molten rock that pour onto the Earth's surface during an effusive eruption. Both moving lava and the resulting solidified deposit are referred to as lava flows. Because of the wide range in the viscosity of the different lava types (basalt, andesite, dacite, and rhyolite), lava discharge during eruptions, and characteristics of the erupting vent and topography over which lava travels, lava flows come in a great variety of shapes and sizes.