Continental crust or continental crust is the continental crust of the continents , which consists of sedimentary , granite and granulite-mafic beds. The average thickness is 35–45 km , the maximum is up to 75 km (under the mountains). It is opposed to the oceanic crust , which is different in structure and composition. The continental crust covers about 40% of the surface of the globe, in volume it makes up about 70% of the entire earth’s crust [1] .
Content
Building
The continental crust has a three-layer structure. The upper layer is represented by a discontinuous cover of sedimentary rocks , which is widely developed, but rarely has a large thickness. Most of the crust is composed of the upper crust - a layer consisting mainly of granites and gneisses , which has a low density and ancient history. Studies show that most of these rocks formed a very long time ago, about 3 billion years ago. Below is the lower crust, consisting of metamorphic rocks - granulites and the like.
Age
The continental crust as a whole is much older than the oceanic crust, whose age does not exceed 200 million years. About 7% of the continental crust is older than 2.5 billion years, and some mineral samples are from 4.0 to 4.4 billion years old [1] .
See also
- Oceanic crust
- Plate tectonics
Literature
- Hain V. E, Lomize M. G. Geotectonics with the basics of geodynamics: A Textbook. - 2nd ed., Rev. and add. - M .: KDU, 2005 .-- 560 p. , 16 p. col. ill .: ill.
Notes
- ↑ 1 2 Hawkesworth CJ et al. The generation and evolution of the continental crust // Russian of the Geological Society : journal. - London, 2010. - Vol. 167 . - P. 229-248 . - DOI : 10.1144 / 0016-76492009-072 .