Craton

Period when the two continents were joined as part of the Pangea supercontinent In geology, a craton ( , , or ; ) is an old and stable part of continental lithosphere (the Earth's two topmost layers, the crust and the lithospheric mantle). Having often survived cycles of merging and rifting of continents, cratons are generally found in the interiors of tectonic plates; the exceptions occur where geologically recent rifting events have separated cratons and created passive margins along their edges. Cratons are composed of ancient crystalline basement rocks covered by younger sedimentary rocks. They have a thick crust and deep lithospheric roots extending several hundred kilometres into Earth's mantle. This crust consists of shields and platforms. Shields are made of basement rock and are visible, while platforms are the portion not visible made up of sedimentary rock. Cratons contain the oldest continental crust rocks on Earth. They were formed in the Archaean (4 to 2.5 billion years ago) and the Proterozoic (2.5 billion- 538.8 million year ago) geologic eons. Most were formed in the Archaean.

Period when the two continents were joined as part of the Pangea supercontinent]] In geology, a craton ( , , or ; ) is an old and stable part of continental lithosphere (the Earth's two topmost layers, the crust and the lithospheric mantle). Having often survived cycles of merging and rifting of continents, cratons are generally found in the interiors of tectonic plates; the exceptions occur where geologically recent rifting events have separated cratons and created passive margins along their edges. Cratons are composed of ancient crystalline basement rocks covered by younger sedimentary rocks. They have a thick crust and deep lithospheric roots extending several hundred kilometres into Earth's mantle. This crust consists of shields and platforms. Shields are made of basement rock and are visible, while platforms are the portion not visible made up of sedimentary rock. Cratons contain the oldest continental crust rocks on Earth. They were formed in the Archaean (4 to 2.5 billion years ago) and the Proterozoic (2.5 billion- 538.8 million year ago) geologic eons. Most were formed in the Archaean. , including the relationship between cratons, shields and platforms (Abbreviations: cb=cratonic basin, LIP=large igneous province, MOR=mid-ocean ridge)]] The process by which cratons were formed is called cratonization. Much about this process remains uncertain, with very little consensus in the scientific community. However, the first cratonic landmasses likely formed during the Archean eon. This is indicated by the age of diamonds, which originate in the roots of cratons and are almost always over 2 billion years and often over 3 billion years in age. Rock of the Archean age makes up only 7% of the world's current cratons; even allowing for erosion and destruction of past formations, this suggests that only 5 to 40 per cent of the present continental crust formed during the Archean. The Archeon eon makes approximately around 3% of the Earth's current surface, but all continents on earth contain crust from it. Cratonization likely was completed during the Proterozoic. Subsequent growth of continents was by accretion at continental margins.

Text derived from https://en.wikipedia.org/w/index.php?oldid=1378614456 under CC BY-SA 4.0; modifications have been made.