Thecontinental rise is a low-relief zone of accumulatedsediments that lies between thecontinental slope and theabyssal plain.[1] It is a major part of thecontinental margin, covering around 10% of the ocean floor.[1][2]
This geologic structure results from deposition of sediments, mainly due tomass wasting, the gravity-driven downhill motion of sand and other sediments.[1] Mass wasting can occur gradually, with sediments accumulating discontinuously, or in large, sudden events.[1] Large mass wasting occurrences are often triggered by sudden events such asearthquakes or oversteepening of the continental slope.[1] More gradual accumulation of sediments occurs whenhemipelagic sediments suspended in the ocean slowly settle to the ocean basin.[1]
Because the continental rise lies below the continental slope and is formed from sediment deposition, it has a very gentle slope, usually ranging from 1:50 to 1:500.[1] As the continental rise extends seaward, the layers of sediment thin, and the rise merges with the abyssal plain, typically forming a slope of around 1:1000.[1]
Deposition of sediments at the mouth of submarinecanyons may form enormous fan-shaped accumulations calledsubmarine fans on both thecontinental slope and continental rise.[2]Alluvial or sedimentary fans are shallow cone-shaped reliefs at the base of the continental slope that merge together, forming the continental rise.[2]
Erosionalsubmarine canyons slope downward and lead to alluvial fan valleys with increasing depth.[2] It is in this zone that sediment is deposited, forming the continental rise. Alluvial fans such as theBengal Fan, which stretches 3,000 kilometers (1,900 miles), make up one of the largest sedimentary structures in the world.[1] Many alluvial fans also contain criticaloil andnatural gas reservoirs, making them key points for the collection of seismic data.[1]
Beyond the continental rise stretches theabyssal plain, which lies on top ofbasaltic oceanic crust and spans the majority of theseafloor.[2] The abyssal plain hosts life forms which are uniquely adapted to survival in its cold, high pressure, and dark conditions.[1] The flatness of the abyssal plain is interrupted by massive underwater mountain chains near thetectonic boundaries of Earth'splates.[2] The sediments are mostlysilt andclay.[1]
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