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An example of a volcanic arc having both island and continental arc sections is found behind the Aleutian Trench subduction zone in Alaska. Volcanoes that occur above subduction zones, such as Mount St. Helens, Mount Etna, and Mount Fuji, lie approximately one hundred kilometers from the trench in arcuate chains called volcanic arcs.
A convergent boundary (also known as a destructive boundary) is an area on Earth where two or more lithospheric plates collide. One plate eventually slides beneath the other, a process known as subduction. The subduction zone can be defined by a plane where many earthquakes occur, called the Wadati–Benioff zone. [1]
The Cascadia subduction zone is a 960 km (600 mi) fault at a convergent plate boundary, about 100–200 km (70–100 mi) off the Pacific coast, that stretches from northern Vancouver Island in Canada to Northern California in the United States.
These are also known as collision boundaries. Subduction zones occur where an oceanic plate meets a continental plate and is pushed underneath it. Subduction zones are marked by oceanic trenches. The descending end of the oceanic plate melts and creates pressure in the mantle, causing volcanoes to form.
Eruptions associated with subducting zones, meanwhile, are driven by subducting plates that add volatiles to the rising plate, lowering its melting point. Each process generates different rock; mid-ocean ridge volcanics are primarily basaltic, whereas subduction flows are mostly calc-alkaline, and more explosive and viscous. [55]
It is a result of the most linear, fastest converging, and seismically active subduction boundary on Earth, the Kermadec–Tonga subduction zone, and consequently has the highest density of submarine volcanoes. [1] The Tonga–Kermadec Ridge stretches more than 3,000 km (1,900 mi) north-northeast from New Zealand's North Island.
The Kermadec–Tonga subduction zone is a convergent plate boundary that stretches from the North Island of New Zealand northward. The formation of the Kermadec and Tonga plates started about 4–5 million years ago. Today, the eastern boundary of the Tonga plate is one of the fastest subduction zones, with a rate up to 24 cm/year (9.4 in/year ...
The eastern boundary is a subduction zone, the Lesser Antilles subduction zone, where oceanic crust of the South American plate is being subducted under the Caribbean plate. Subduction forms the volcanic islands of the Lesser Antilles Volcanic Arc from the Virgin Islands in the north to the islands off the coast of Venezuela in the south.