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Oceanic crust is formed at an oceanic ridge, while the lithosphere is subducted back into the asthenosphere at trenches. Oceanic trenches are prominent, long, narrow topographic depressions of the ocean floor. They are typically 50 to 100 kilometers (30 to 60 mi) wide and 3 to 4 km (1.9 to 2.5 mi) below the level of the surrounding oceanic ...
The continental shelf is the relatively shallow water area found in proximity to continents; it is the portion of the continental margin that transitions from the shore out towards to ocean. Continental shelves are believed to make up 7% of the sea floor. [3] The width of continental shelves worldwide varies in the range of 0.03–1500 km. [4]
The crust that lies below sea level is known as the oceanic crust, while on land it is known as the continental crust. The former is thinner and is composed of relatively dense basalt, while the latter is less dense and mainly composed of granite. The lithosphere is composed of the crust (oceanic and continental) and the uppermost part of the ...
He concluded that the cause of the earthquake was a megathrust reaction in the Aleutian Trench, a result of the Alaskan continental crust overlapping the Pacific oceanic crust. This meant that the Pacific crust was being forced downward, or subducted , beneath the Alaskan crust.
Continental and oceanic crust on the Earth's upper mantle. Oceanic crust is the uppermost layer of the oceanic portion of the tectonic plates. It is composed of the upper oceanic crust, with pillow lavas and a dike complex, and the lower oceanic crust, composed of troctolite, gabbro and ultramafic cumulates.
Depth of oceanic trenches seems to be controlled by age of the oceanic lithosphere being subducted. [5] Sediment fill in oceanic trenches varies and generally depends on abundance of sediment input from surrounding areas. An oceanic trench, the Mariana Trench, is the deepest point of the ocean at a depth of approximately 11,000 m (36,089 ft).
An abyssal plain is an underwater plain on the deep ocean floor, usually found at depths between 3,000 and 6,000 metres (9,800 and 19,700 ft).Lying generally between the foot of a continental rise and a mid-ocean ridge, abyssal plains cover more than 50% of the Earth's surface.
At the deepest point, the trench is nearly 11,000 m deep (almost 36,000 feet). [38] [3] This is further below sea level than Mount Everest is above sea level, by over 2 kilometers. Volcanic arcs and oceanic trenches partly encircling the Pacific Basin form the so-called Pacific Ring of fire, a zone of frequent earthquakes and volcanic eruptions.