ABSTRACT
Magma may be extruded on to the Earth’s surface or intruded into country rock, which is an existing rock into which a new rock is introduced or found. Lava extruded from volcanic vents may build landforms directly. On the other hand, lava could be buried beneath sediments, be re-exposed by erosion at a later date, and then influence land - form development. Intruded rocks, which must be mobile but not necessarily molten, may have a direct effect on landforms by causing doming of the surface, but otherwise they do not create landforms until they are exposed by erosion.
