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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]
Block view of a rift formed of three segments, showing the location of the accommodation zones between them at changes in fault location or polarity (dip direction) Gulf of Suez Rift showing main extensional faults. In geology, a rift is a linear zone where the lithosphere is being pulled apart [1] [2] and is an example of extensional tectonics ...
Rift phase lavas cover most of the island, not only forming the ridges along each rift zone but also partially infilling the landslide bays. The rift zones extend outwards as submarine volcanic ridges on the ocean floor; for example, the south-south-east rift zone extends underwater to at least 40 km (25 mi) south of the island. [223]
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 ...
Rift zones are a prominent feature on these volcanoes and account for their seemingly random volcanic structure. [7] They are fueled by the movement of the Pacific Plate over the Hawaii hotspot and form a long chain of volcanoes, atolls , and seamounts 2,600 km (1,616 mi) long with a total volume of over 750,000 km 3 (179,935 cu mi).
The dikes that feed fissures reach the surface from depths of a few kilometers and connect them to deeper magma reservoirs, often under volcanic centers. Fissures are usually found in or along rifts and rift zones, such as Iceland and the East African Rift. Fissure vents are often part of the structure of shield volcanoes. [2] [3]
The northern rift zone of Axial Seamount is a 5 km (3 mi) long ridge running 10 to 20 degrees northeast of the main caldera. The rift is pocketed by multiple fissures , 100–200 m (328–656 ft) in length, as far as 7 km (4 mi) from Axial Volcano's center, and reaching up to 400 m (1,312 ft) long and 20 m (66 ft) deep.
At some volcanoes, flank eruptions are common, and occur along clearly defined rift zones. This is the case at Mauna Loa and Kilauea volcanoes in Hawaii, Piton de la Fournaise on Reunion Island, [1] and Mount Etna in Italy. [2] Flank and summit eruptions may occur at the same time. [3]