5.2.2. Volcanism

Volcanism includes the movement of molten rock (magma) onto or toward the earth’s surface and also formation of many intrusive and extrusive volcanic forms. The layer below the solid crust is mantle which contains a weaker zone called asthenosphere. It is from this that the molten rock material finds their way to the surface. The material in the upper mantle portion is called magma. The magma is conveyed to the surface essentially along tube-like conduits and the extrusion of lava builds distinctive conical or dome shaped landforms.