Rift

"Chasm" redirects here. For other uses, see Chasm (disambiguation).

For other uses, see Rift (disambiguation).

USGS image

Plates in the crust of the earth, according to the plate tectonics theory

Gulf of Suez rift showing main extensional faults

In geology, a rift or chasm is a place where the Earth's crust and lithosphere are being pulled apart^[1] and is an example of extensional tectonics.^[2]

Typical rift features are a central linear downfaulted segment, called a graben, with parallel normal faulting and rift-flank uplifts on either side forming a rift valley, where the rift remains above sea level. The axis of the rift area commonly contains volcanic rocks, and active volcanism is a part of many, but not all active rift systems.

Major rifts occur along the central axis of mid-ocean ridges, where new oceanic crust and lithosphere is created along a divergent boundary between two tectonic plates.

Failed rifts are where continental rifting began, but then failed to continue to the point of break-up. Typically the transition from rifting to spreading develops at a triple junction where three converging rifts meet over a hotspot. Two of these evolve to the point of seafloor spreading, while the third ultimately fails, becoming an aulacogen.

Examples

• The East African Rift
• The Red Sea Rift
• The Baikal Rift Zone, the bottom of Lake Baikal is the deepest continental rift on the earth.
• The Gulf of Suez Rift
• Lake Timiskaming in Temiskaming Shores, Ontario
• Throughout the Basin and Range Province in North America
• The Rio Grande Rift in the southwestern US
• The rift zone that contains the Gulf of Corinth in Greece
• The Reelfoot Rift, an ancient buried failed rift underlying the New Madrid Seismic Zone in the Mississippi embayment
• The Rhine Rift, in south western Germany, known as the Upper Rhine valley, part of the European Cenozoic Rift System
• The Taupo Volcanic Zone in the north east North Island of New Zealand
• The Oslo Graben in Norway
• The Ottawa-Bonnechere Graben in Ontario and Quebec
• The Northern Cordilleran Volcanic Province in British Columbia, Yukon and Alaska
• The West Antarctic Rift in Antarctica
• The Midcontinent Rift System, a late Precambrian rift in central North America
• The Fundy Basin, a Triassic rift basin in southeastern Canada
• The Narmada Rift valley in peninsular India

See also

• Rift zone

References

1. ^ Decompressional Melting During Extension of Continental Lithosphere, Jolante van Wijk, MantlePlumes.org
2. ^ Plate Tectonics: Lecture 2, Geology Department at University of Leicester