Magma; Molten rock
Lava is molten rock that reaches the Earth’s surface through a volcano or fissure. When the molten rock solidifies the resulting rock is called igneous rock. The igneous rock can originate from different sources. Some rocks originate deep in the Earth’s mantle whereas others can originate high within the Earth’s crust directly underneath a vent. Dependent on the origin, the composition of the crystallized rock is different and therefore provides some hint where the rock came from and what the interior of the Earth looks like.
The erupted lavas usually can be distinguished into three major types: basaltic, andesitic, and rhyolitic lava. Basaltic lava is an extrusive rock of “mafic” composition (high in iron, magnesium, and calcium) with relatively low silica content, andesitic lava has an intermediate silica content, and finally rhyolitic lava has a “felsic” composition (high in sodium and potassium) with silica content greater than 68 vol%.