Configuration of Ocean floor UPSC | Relief of the Ocean floor| Oceanography | Physical Geography

Relief of the Ocean floor:

The oceans are located in the great depressions of the Earth's outer layer (crust). Unlike continents, oceans naturally merge with other oceans so much that it becomes very difficult to demarcate them. Nevertheless, geographers have divided the Earth's ocean into five oceans, which are named as follows -

• Pacific Ocean
• Atlantic ocean
• Indian Ocean
• Southern Ocean
• Arctic Ocean

The land under the waters of the ocean is named the ocean floor. The average depth of the ocean floor is about 3 to 6 km below sea level. The ocean floor has many complex and varied features like plains, mountain ranges, trenches, etc, and these are formed by tectonic processes, volcanic eruptions, and depositional processes. 

The ocean floor may be divided into three major divisions based on depth as well as relief. Three major divisions are:

• Continental Margin
• Deep-Sea basin or Abyssal plain
• Mid Ocean ridges

Continental margin:

The continental margin lies between the continents' shores and deep-sea basins.

It includes:

• Continental shelf
• Continental slope
• Continental rise
• Deep Ocean trenches

Continental shelf:

• It is an extended margin of each continent occupied by shallow seawater. The continental shelf ends with a very steep slope called the shelf break.
• The width of the continental shelf varies from ocean to ocean and continent to continent, but the average width is approx 80 km.
• There is narrow shelf width along with Chile's coast and the west coast of Sumatra and the largest shelf width having 1500 km is the Siberian shelf in the Arctic ocean.
• The continent's shelf is covered with various sediments of different periods that are brought by rivers, glaciers, and winds from land and distributed by waves and currents.
• Massive sediments are received over longer times from the continent and become the sources of fossil fuels.
• We get much knowledge about the climate of the surrounding region over the geological time scale by analyzing the deposition on the continental shelves.

Continental slope:

• The Continental slope lies between the continental shelf and the ocean basin. It starts with the steep slope of the continental shelf. The Continental slope boundary indicates the end of continents.
• Canyons and trenches are found in this region

Continental rise:

• Continental rise lies between the continental slope and the abyssal plains. It is made up of sediments that come from the continental shelf.

Oceanic Deeps or ocean trenches:

• It is the deepest part of the ocean characterized by steep sides and narrow basins.
• It is generally 3-5 km deeper than the surrounding ocean floor.
• It is found near the Islands arc associated with Volcanos.
• There are 57 known deep trenches in the world:
• 32 are in the Pacific Ocean
• 19 are in the Atlantic Ocean
• 6 are in the Indian Ocean

Deep-sea basin or Abyssal plains:

• It is extensive plains that lie between the continental margin and mid-oceanic ridges.
• Some fined grains sediments such as clay and silt from the continental margin also get accumulated in these areas.

Mid-Oceanic ridges:

• The mid-ocean ridge consists of two ranges of mountains separated by a large trough( depression). It is an interconnected series of mountain systems within the ocean. The peaks of mountain ranges can be so high that they even reach above the surface of the sea. Iceland is part of the Mid-Atlantic Ridge.
• It is a feature of the central rift system called the crest. Intense volcanic activity occurs in rift systems at the summit.

The following minor forms are found within Mid-Oceanic ridges and Abyssal plains ( Deep ocean plains):

• Seamounts
• Islands
• Guyots
• Atolls
• Submarine Canyons

Seamounts:

• It is the mountain with a pointed summit, that rises from the seafloor but does not reach the surface of the ocean. These are volcanos' origins.
• For example, Emperor seamount, the extension of the Hawaiian Islands in the pacific ocean is an example of a Seamount.

Islands:

• When the seamount reaches above sea level then it becomes islands.

Guyots:

• It is a flat-topped seamount. Due to subsidence, it becomes flat-topped, About more than 10,000 Guyots exist alone in the pacific ocean.

Atolls:

• These are low islands with coral reefs found in tropical oceans that surround deep depressions.

Submarine Canyons:

• These are deep valleys; these are found cutting across the continental shelves and slopes starting from the mouth of the river. Examples; Hudson Canyon is the best example.

You may like also:

• Bottom topography of the Indian Ocean
• Configuration of Ocean floor
• Bottom topography of the Pacific Ocean
• Bottom topography of the Atlantic Ocean 
• समुद्रतल का उच्चावच स्वरूप | महासागरीय अधस्तल का उच्चावच UPSC | 

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