In volcanology, magma is melted rock that is under the ground. Magma is the molten rocks in Earth's mantle. Magma exists as pockets and plumes beneath the surface of the Earth. Magma is a molten and semi-molten rock mixture found under the surface of the Earth. This mixture is usually made up of four parts: a hot liquid base, called the melt; minerals crystallized by the melt; solid rocks incorporated into the melt from the surrounding confines; and dissolved gases.