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A rift zone is a feature of some volcanoes, especially shield volcanoes, in which a set of linear cracks (or rifts) develops in a volcanic edifice, typically forming into two or three well-defined regions along the flanks of the vent. [1]
In geology, a rift is a linear zone where the lithosphere is being pulled apart [1] [2] and is an example of extensional tectonics. [3] 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. [ 4 ]
A dike swarm (American spelling) or dyke swarm (British spelling) is a large geological structure consisting of a major group of parallel, linear, or radially oriented magmatic dikes intruded within continental crust or central volcanoes in rift zones. Examples exist in Iceland [1] and near other large volcanoes, (stratovolcanoes, calderas ...
Typical examples include the development of calderas and resurgences, pit craters, dikes, sills, laccoliths, magma chambers, eruptive fissures, volcanic rift zones and any type of volcano flank dynamics, including sector collapses. In the second case, the process controlling the magma may have a regional extent, also outside the volcanic area.
Divergent boundaries are typified in the oceanic lithosphere by the rifts of the oceanic ridge system, including the Mid-Atlantic Ridge and the East Pacific Rise, and in the continental lithosphere by rift valleys such as the famous East African Great Rift Valley. Divergent boundaries can create massive fault zones in the oceanic ridge system.
Young volcanoes are rarely found within cratons, but are characteristic of subduction zones, rift zones, or in ocean basins. Intraplate volcanoes are clustered along hotspot traces. [2] Within regions of volcanic activity, volcanic fields are clusters of volcanoes that share a common magma source. [3]
When it does reach the surface, however, a volcano is formed. Thus subduction zones are bordered by chains of volcanoes called volcanic arcs. Typical examples are the volcanoes in the Pacific Ring of Fire, such as the Cascade Volcanoes or the Japanese Archipelago, or the eastern islands of Indonesia. [16] [2]
A map of East Africa showing some of the historically active volcanoes (as red triangles) and the Afar Triangle (shaded at the center), which is a so-called triple junction (or triple point) where three plates are pulling away from one another: the Arabian plate and two parts of the African plate—the Nubian and Somali—splitting along the East African Rift Zone Main rift faults, plates ...