Continental Shelf

 

Continental Shelf:

  • There is no clear or well-defined line separating oceans from continents.
  • Infact, continents do not end abruptly at shoreline.
  • They slope seaward from the coast to a point where the slope becomes very steep.
  • The shallow submerged extension of continent is called the continental shelf.
  • The depth of this shallow sea water over the continental shelf ranges between 120 to 370 metres.
  • The width of the continental shelf varies greatly ranging between a few kilometres to more than 100 kilometres.
  • This variation can be seen even in the context of Indian peninsula.
  • The continental shelf off the eastern coast of India is much wider than that of the western coast.
  • Similar variations are seen all over the world.
  • Off the coast of West Europe, it extends to 320 kilometres from the Cape of Land’s End. Off the coast of Florida the shelf is 240 kilometres wide.
  • They are much narrower or absent in some continents, particularly where fold mountains run parallel or close to the coast as along the eastern Pacific Ocean.
  • Most of the continental shelves represent land which has been inundated by a rise in sea level.
  • Many regard their formation due to the erosional work of waves or due to the extension of land by the deposition of river borne material on the off-shore terraces.
  • Off the coast regions which were once covered by ice sheets, they may have developed due to glacial deposits.

Continental shelf

 

Importance of continental shelves:

  • The continental shelves are of great importance to man.
  • The shallow water over the shelf enables sunlight to penetrate through the water to the bottom and encourages growth of microscopic plants and animals called planktons.
  • These planktons are the food for fishes.
  • Continental shelves are the source of fishes, mineral including sand and gravel.
  • A large quantity of the world’s petroleum and natural gas is obtained from these shelves.
  • The Bombay High and the discovery of petroleum in the Godavari basin are examples of on shore drilling on the continental shelf.
  • Coral reefs and lipoclastic materials are also common on continental shelves.

 

Submarine canyons

Submarine canyons

 

 

  • One of the striking features of the continental shelf is the presence of submarine canyons which extend to the continental slope.
  • These canyons are ‘steepsided valleys’ cut into the floor of the seas.
  • They are very similar to the gorges found on the continents.
  • Godavari Canyon in front of the Godavari river mouth is 502 metres deep.
  • One of the reasons for the formation of submarine canyon is underwater landslide.
  • The sediments collected on the continental shelves get dislodged by a storm or a earthquake. The force of these moving sediments erode the slopes as they come down and as a result submarine canyons are carved out.
  • The continental shelf is generally considered to be territorial water extent of the nations to which it adjoins.