Essay by angel_no7 January 2007

download word file, 2 pages 5.0

All rocks are ultimately derived from igneous rock. Do you agree with this statement? Discuss with specific reference to the rock cycle.

The Earth's crust is composed of different kinds of rocks, which are composed of minerals. Rocks are divided into three major groups, depending on their origin - igneous, sedimentary and metamorphic. All rocks are stages in a never-ending cycle, the rock cycle, which continuously refashions, redistributes and recycles existing crustal material.

The Earth's surface is subject to constant change. Some of this is driven by sub-surface processes such as, plate tectonics, folding, faulting and volcanic activities, which tend to raise the surface. However, some of the change is driven by surface processes such as weathering and erosion which tend to lower the surface. The rock cycle works non-stop building up and wearing down the Earth's surface materials.

The ultimate source of all rocks on the Earth's surface is magma.

Igneous rocks are formed when molten magma cools and solidifies, either underground or on the surface which results in having intrusive and extrusive igneous rocks. These rocks are constantly being destroyed and created. Once they are exposed at the surface they are weathered, mainly by the action of rain, frost and wind. There are various weathering processes which include salt weathering, frost weathering, insolation weathering, root-wedging and organic weathering amongst others. This is a very good example of denudation where weathering prepares material for transport, and mass wasting and erosion move that material downhill towards an ultimate base level, normally the sea. The movement of rock particles is done by active transporting agents such as running water, moving ice or blowing wind. If sedimentation continues, more material is buried till finally, the sediments are compressed and cemented together to form sedimentary rocks.

Other igneous rocks are transformed...