The oldest rocks in a given area. A large volcanic depression at the summit of a volcano, caused by collapse or explosion. A conical hill formed of volcanic cinders. A mechanism of heat transfer from the interior to the exterior of a medium, in which hot material rises, because of its lower density, and cooler material sinks. A band along which moving plates collide and area is lost either by shortening and crustal thickening or by subduction and destruction of crust.
Convergence zones are sites of earthquakes, volcanism, trenches, and mountain building.
An abrupt circular depression formed by extrusion of volcanic material and its deposition in a surrounding rim, or by explosive ejection of material on meteorite impact. The outermost layer of the lithosphere. A general lowering of the surface by processes of erosion. A roughly planar body of intrusive igneous rock. The angle that a surface makes with the horizontal, measured perpendicular to the strike.