Home Geography Vocabulary Continental Slope : An Overview

Continental Slope : An Overview

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Seamount. Continental. rise. Abyssal plain. trench. mid-ocean. ridge. Rift valley.

Continental slope:-
Continental slope is an area of a steep slope which extend from the continental shelf break to the deep sea plain.

Like Continental shelf, Continental slope is geologically not a part of the ocean crust but forms an integral part of the continental margins which is covered by oceans. The extent of the continental slope usually varies from 200 to 2000 meter depth though it covers very small part of the ocean floor.

Continental slopes are by far, the longest and the highest slopes on the earth. The exact nature of the continental slope and its characteristics have been studied by the sonic soundings and the resulting profile Shepard (1841) based on his observation on 500 profiles of different part of the ocean and concluded that the average slope is about 4.3 degree although near the continental break, it ranges from 1 Degree to 10 degrees. There are large variations in the angle of slope from one place to another.

 

For example in areas where the mountain ranges border the cost it is 6 degree  and where there are faults along the shoreline it is 5 degree to 6 degree. Along the well-drained coastal plains for in areas of measure deltas the slope is about 1.3 degree and along the stable coasts it varies from 2 degree to 3.5 degree.

The mature of Continental slope and its distance from the cost depends upon topography of the ocean floor. In the Atlantic ocean at 51 degree 30 minutes North latitude the continental slope starts after a distance of 80 kilometre from the cost and extends up to 400 km up to a depth of 1833 m. Here  the slope is about 5 degree on Calicut cost of India, the slope varies from 5 degree to 15 degree.

Other examples of steep Continental slopes are of the Spanish coast (30 degree) Tristan da Cunha (33 degree) near Saint Helena and near Saint Paul (62 degree) In general, the gradient decreases as the slope merges with deep sea  floor at depth of about 3000 to 4000 metre. Normally Continental slopes do not favour thick deposits of marine materials due to steep slope but in certain cases, there is a thin veneer of deposits on these slopes.


As the material excavated by the tributary current reaches the bottom of the continental slope, its speed is reduced and it cannot be transported further.Consequently the material is deposited at the base of the continental slope in the form of a fan, more or less similar to a fans produced by the rivers on the land.These are known as deep sea fans. The base of the deep sea fan is at the base of the continental slope and its apex points towards the mouth of the submarine Canyon.

These fans extend to a distance of over 500 kilometers and are Laden by material brought by the tributary currents. These are graded deposits in which coarse materials are overlain by successive layers of materials comprising of smaller particles. Such graded deposits are known as turbidites because they are deposited by turbidity currents.

Several fans have deep channels. These channels are simply extensions of submarine Canyons cut in the continental slope. The channels develop levels similar to those formed by rivers on the land.

Some of the largest train in the world is found in the Indian ocean beyond the deltas of the Ganga and Indus. Other large fans are Amazon and Congo fans in the South Atlantic Ocean, Mississippi fans in the Gulf of Mexico, the Laurentian fan in the North Atlantic and the number of smaller fans off of the Pacific coast of North America.

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