rock cycle

Click a letter for the index

Or search the encyclopaedia:

 

 

Go

 

The recycling of the Earth's outer layers. Rocks are continually being formed, destroyed, and re-formed in an endless cycle of change that takes millions of years. The processes involved include the formation of igneous rock from magma (molten rock); surface weathering and erosion; the compaction and cementation of sediments into sedimentary rock; and metamorphism, chemical and physical changes brought about by heat and pressure, producing metamorphic rock.

Ghana was the first country to adopt the pan-African colours. The star is known as the ‘lode star of African freedom’. Effective date: 28 February 1966. >>