Rift valley

A rift valley is a linear-shaped lowland between several highlands or mountain ranges created by the action of a geologic rift or fault. A rift valley is formed on a divergent plate boundary, a crustal extension, a spreading apart of the surface, which is subsequently further deepened by the forces of erosion. When the tensional forces were strong enough to cause the plate to split apart, a center block dropped between the two blocks at its flanks, forming a graben. The drop of the center creates the nearly parallel steeply dipping walls of a rift valley when it is new. That feature is the beginning of the rift valley, but as the process continues, the valley widens, until it becomes a large basin that fills with sediment from the rift walls and the surrounding area. One of the best known examples of this process is the East African Rift. On Earth, rifts can occur at all elevations, from the sea floor to plateaus and mountain range in continental crust or in oceanic crust. They are often associated with a number of adjoining subsidiary or co-extensive valleys, which are typically considered part of the principal rift valley geologically.

Rift Valley

In order of specificity, Rift Valley can refer to:

Great Rift

Great Rift may mean:

Geography

Astronomy

Fictional

Great Rift Valley

The Great Rift Valley is a name given to the continuous geographic trench, approximately 6,000 kilometres (3,700 mi) in length, that runs from Lebanon's Beqaa Valley in Asia to Mozambique in South Eastern Africa. The name continues in some usages, although it is today considered geologically imprecise as it combines features that are today regarded as separate, although related, rift and fault systems.

Today, the term is most often used to refer to the valley of the East African Rift, the divergent plate boundary which extends from the Afar Triple Junction southward across eastern Africa, and is in the process of splitting the African Plate into two new separate plates. Geologists generally refer to these incipient plates as the Nubian Plate and the Somali Plate.

Theoretical extent

The Great Rift Valley as originally described was thought to extend from Lebanon in the north to Mozambique in the south, where it constitutes one of two distinct physiographic provinces of the East African mountains. It included what we would call today the Lebanese section of the Dead Sea Transform, the Jordan Rift Valley, Red Sea Rift and the East African Rift.

Rift

In geology, a rift is a linear zone where the Earth's crust and lithosphere are being pulled apart and is an example of extensional tectonics.

Typical rift features are a central linear downfaulted depression, called a graben, or more commonly a half-graben with normal faulting and rift-flank uplifts mainly on one side. Where rifts remain above sea level they form a rift valley, which may be filled by water forming a rift lake. The axis of the rift area may contain volcanic rocks, and active volcanism is a part of many, but not all active rift systems.

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

Failed rifts are the result of continental rifting that 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.