In geology, a rift is caused by tectonic plates in the Earth's lithosphere moving apart. Rifts are usually accompanied by orogeny (mountain building), volcanoes and earthquakes. Rifting often makes a rift valley, which may hold a rift lake. The Great Rift Valley in East Africa is an example.
A rift is the result of the pulling apart or extension of the crust and lithosphere. Mantle upwelling brings hotter asthenosphere up into the colder lithosphere. Sometime it comes out as lava. This rise occurs with the thinning and stretching of the lithosphere.
- http://www.mantleplumes.org/VM_DecompressMelt.html Decompressional Melting During Extension of Continental Lithosphere
- http://www.le.ac.uk/geology/art/gl209/lecture4/lecture4.html Plate Tectonics: Lecture 2