Molten Rock Magma - underground molten rock and dissolved gas. Forms intrusive igneous rock. Lava - magma that erupts above ground.
Forms extrusive igneous rock.
Rhyolite is Low Temp. Basaltic is High Temp. As a lava loses gas, it becomes More Viscous. 64 mm Tuff is name of a rock formed of ash and lapilli. May be fairly common.