Plate tectonics

The tectonic plates of the world were mapped in the second half of the 20th century.

Plate tectonics) is a theory of geology. It has been developed to explain for large scale motions of the Earth's lithosphere. This theory replaces the older theory of continental drift from the first half of the 20th century and the concept of seafloor spreading that was developed during the 1960s.

Following this theory the outermost part of the Earth's interior is made up of two layers: above is the lithosphere, which includes the crust and the rigid uppermost part of the mantle. Below the lithosphere lies the asthenosphere. Although solid, the asthenosphere has relatively low viscosity and shear strength and can flow like a liquid on geological time scales. The deeper mantle below the asthenosphere is more rigid again. This is, however, due not to cooler temperatures but to high pressure.

The lithosphere is broken up into what are called tectonic plates—in the case of Earth, there are seven major and many minor plates (see list below). The lithospheric plates ride on the asthenosphere. These plates move in relation to one another at one of three types of plate boundaries: convergent or collision boundaries, divergent or spreading boundaries, and transform boundaries. Earthquakes, volcanic activity, mountain-building, and oceanic trench formation occur along plate boundaries. The lateral movement of the plates is typically at speeds of 0.66 to 8.50 centimeters per year.

See also

• List of plate tectonics topics
• List of tectonic plates
• List of tectonic plate interactions
• Geosyncline theory, obsolete explanation of mountain-building
• Plume tectonics, an extension of plate tectonics that attempts to explain other aspects of the field

References

• McKnight, Tom (2004) Geographica: The complete illustrated Atlas of the world, Barnes and Noble Books; New York ISBN 0-7607-5974-X
• Oreskes, Naomi ed. (2003) Plate Tectonics : An Insider's History of the Modern Theory of the Earth, Westview Press ISBN 0-8133-4132-9
• G. Schubert, DL Turcotte, and P. Olson (2001) Mantle Convection in the Earth and Planets, Cambridge University Press, Cambridge, ISBN 0-521-35367-X
• Stanley, Steven M. (1999) Earth System History, W.H. Freeman and Company; pages 211–228 ISBN 0-7167-2882-6
• Tanimoto, Toshiro and Thorne Lay (2000) Mantle dynamics and seismic tomography, Proc. Natl. Acad. Sci. USA, 10.1073/pnas.210382197 http://www.pnas.org/cgi/content/full/97/23/12409 Accessed 03/29/06.
• Thompson, Graham R. and Turk, Jonathan, (1991) Modern Physical Geology, Saunders College Publishing ISBN 0-03-025398-5
• Turcotte, DL and Schubert, G. (2002) Geodynamics: Second Edition, John Wiley & Sons, New York, ISBN 0-521-66624-4
• Winchester, Simon (2003) Krakatoa: The Day the World Exploded: August 27, 1883, HarperCollins ISBN 0-06-621285-5
• SJ Moss, MEJ Wilson. 1998. Biogeographic implications of the Tertiary palaeogeographic evolution of Sulawesi and Borneo. Biogeography and geological evolution of SE Asia.

External links

• Movie showing 750 million years of global tectonic activity.
• More movies over smaller regions and smaller time scales.
• Easy-to-draw illustrations for teaching plate tectonics
• An explanation of tectonic forces
• Bird, P. (2003) An updated digital model of plate boundaries also available as a large (13 mb) PDF file [1]
• Map of tectonic plates
• MantlePlumes.org, the website that hosts the debate concerning whether deep mantle plumes exist or notTemplate:Link FATemplate:Link FATemplate:Link FATemplate:Link FA