Lava

Lava is rock from a magma released in more or less fluid form by erupting volcanoes. These rocks are rich in silica (basic rocks). Their temperature varies from 700° to 1200°C and there may be releases of gases such as sulphur dioxide or carbon dioxide. Their composition and appearance vary depending on how the magma was formed.

Volcanic rocks are always rocks from eruptions, and are igneous rocks, together with plutonic rocks, crystallised deep down (like granite). The accumulation of lava flows and other erupted matter (volcanic bombs, ash and lapilli) builds up the characteristic volcano cone of which the shape depends on the viscosity of the lava and/or its gas content.