After surviving cycles of merging and rifting of continents, cratons are usually found in the interiors of tectonic plates. They are composed of ancient crystalline basement rock, which may be covered by younger sedimentary rock. They have a thick crust and deep roots that extend as much as several hundred kilometers into the Earth's mantle.
Cratonic lithosphere is much older than oceanic lithosphere – up to 4 billion years versus 180 million years.
The term craton is used to distinguish the stable portion of the continental crust from regions that are more geologically active and unstable. Cratons can be described as shields, in which the basement rock crops out at the surface, and platforms, in which the basement is overlain by sediments and sedimentary rock.
Cratons are subdivided geographically into geologic provinces. A geologic province is an area with common geologic properties.
- Stanley, Steven M. (1999). Earth system history. New York: W.H. Freeman. pp. 297–302. ISBN 0-7167-2882-6.
- Petit, Charles (18 December 2010). "Continental hearts - Science News". Science News (Society for Science & the Public) 178 (13): 22–26. ISSN 0036-8423. http://www.sciencenews.org/view/feature/id/66927/title/Continental_Hearts. Retrieved 2011-01-08. p25