Ashoka Seamount, Chandragupta Ridge and Kalpataru Ridge

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Context: Three underwater geographical structures located in the Indian Ocean have been awarded names proposed by India.

Details

The discovery

• Kalpataru ridge(430 sq km) and Ashok seamount(180 sqkm): With the help of the Russian Sea vessel Akademik Nikolay Strakhov that the Indian research team discovered both the structures in 2012.
• Chandragupt ridge( 675 sq km): Discovered in 2020 by the Indian ocean research vessel MGS Sagar. It is an elongated and oval shaped body.

Recent naming

• Names ofAshoka Seamount, Chandragupta Ridge and Kalpataru Ridge in the Indian Ocean have been approved by International Hydrographic Organization (IHO) and UNESCO’s Intergovernmental Oceanographic Commission (IOC). 
• These structures are located along Southwest Indian Ridge. 
• They were discovered by National Centre for Polar and Ocean Research.

Other structures bearing Indian names:

• The Raman ridge (accepted in 1992): Discovered in 1951 by a US oil vessel. It was named after Physicist and Nobel Laureate Sir CV Raman.
• The Panikkar Seamount (accepted in 1993): In 1992 it was discovered by India research vessel Sagar Kanya. It is named after NK Panikkar, a renowned oceanographer.
• Sagar Kanya seamount (accepted in 1991): For its successful 22nd cruise in 1986 leading to its discovery, a seamount was named after the research vessel itself.
• DN Wadia Guyot: Geologist DN Wadia was honoured when an underwater volcanic mountain, known as guyot, was named after him in 1993 following its discovery in 1992 by Sagar Kanya.

Naming of Undersea Feature 

Outside Territorial Sea: 

• Individuals and agencies can proposenames for unnamed features, following International Hydrographic Organization (IHO) ’s 2013 guidelines that is  B6 (Standardization Of Undersea Feature Names, 2013). 
• Prior to the naming of a feature, its character, extent, and position shall have been established sufficiently for identification. Positions should be given as geographic coordinates.
• Proposals arereviewed by IHO Sub-Committee on Undersea Feature Names (SCUFN).

Within National Territorial Sea:

• National authorities approving names of features should regularly publicize their decisions.
• National authorities naming features within their territorial sea should conform to the principles and procedures stated in B6 (Standardization Of Undersea Feature Names, 2013). 

Relief of the Ocean Floor

Introduction

• The oceans are confined to the great depressions of the earth’s outer layer. The oceans, unlike the continents, merge so naturally into one another that it is hard to demarcate them. The ‘land’ under the waters of the oceans, that is, the ocean floor exhibits complex and varied features as those observed over the land.
• A major portion of the ocean floor is found between 3-6 km below the sea level.
• The floors of the oceans are rugged with the world’s largest mountain ranges, deepest trenches and the largest plains.

Factors responsible for relief formation

• These features are formed, like those of the continents, by the factors of tectonic, volcanic and depositional processes.

Divisions of the Ocean Floors

• The ocean floors can be divided into four major divisions: the Continental Shelf; the Continental Slope; the Deep Sea Plain;  the Oceanic Deeps.
• Besides, these divisions there are also major and minor relief features in the ocean floors like ridges, hills, sea mounts, guyots, trenches, canyons, etc.

Continental Shelf

• The continental shelf is the extended margin of each continent occupied by relatively shallow seas and gulfs.
• It is the shallowest part of the ocean showing an average gradient of 1° or even less.
• The shelf typically ends at a very steep slope, called the shelf break.
• The width of the continental shelves vary from one ocean to another.
• The average width of continental shelves is about 80 km.
• The shelves are almost absent or very narrow along some of the margins like the coasts of Chile, the west coast of Sumatra, etc.
• On the contrary, the Siberian shelf in the Arctic Ocean, the largest in the world, stretches to 1,500 km in width.
• The depth of the shelves also varies.
• It may be as shallow as 30 m in some areas while in some areas it is as deep as 600 m.
• The continental shelves are covered with variable thicknesses of sediments brought down by rivers, glaciers, wind, from the land and distributed by waves and currents.
• Massive sedimentary deposits received over a long time by the continental shelves, become the source of fossil fuels.

Continental Slope

• The continental slope connects the continental shelf and the ocean basins.
• It begins where the bottom of the continental shelf sharply drops off into a steep slope.
• The gradient of the slope region varies between 2-5°.
• The depth of the slope region varies between 200 and 3,000 m.
• The slope boundary indicates the end of the continents.
• Canyons and trenches are observed in this region.

 Deep Sea Plain

• Deep sea plains are gently sloping areas of the ocean basins.
• These are the flattest and smoothest regions of the world.
• The depths vary between 3,000 and 6,000m.
• These plains are covered with fine-grained sediments like clay and silt.

Oceanic Deeps or Trenches

• These areas are the deepest parts of the oceans.
• The trenches are relatively steep sided, narrow basins.
• They are some 3-5 km deeper than the surrounding ocean floor.
• They occur at the bases of continental slopes and along island arcs and are associated with active volcanoes and strong earthquakes.
• That is why they are very significant in the study of plate movements.
• As many as 57 deeps have been explored so far; of which 32 are in the Pacific Ocean; 19 in the Atlantic Ocean and 6 in the Indian Ocean.

Minor Relief Features

Mid-Oceanic Ridges

• A mid-oceanic ridge is composed of two chains of mountains separated by a large depression.
• The mountain ranges can have peaks as high as 2,500 m and some even reach above the ocean’s surface.
• Iceland, Atlantic Ridge, is an example.

Seamount

• It is a mountain with pointed summits, rising from the seafloor that does not reach the surface of the ocean.
• Seamounts are volcanic in origin.
• These can be 3,000-4,500 m tall.
• The Emperor seamount, an extension of the Hawaiian Islands in the Pacific Ocean, is a good example.

Submarine Canyons

• These are deep valleys, some comparable to the Grand Canyon of the Colorado river.
• They are sometimes found cutting across the continental shelves and slopes, often extending from the mouths of large rivers.
• The Hudson Canyon is the best known submarine canyon in the world.

Guyots

• It is a flat topped seamount.
• They show evidences of gradual subsidence through stages to become flat topped submerged mountains.
• It is estimated that more than 10,000 seamounts and guyots exist in the Pacific Ocean alone.

Atoll

• These are low islands found in the tropical oceans consisting of coral reefs surrounding a central depression.
• It may be a part of the sea (lagoon), or sometimes form enclosing a body of fresh, brackish, or highly saline water.

 

International Hydrographic Organization (IHO)

Established in 1921. 

An intergovernmental body. 

India is a member. 

Enjoys observer status at the UN. 

Recognized as competent international authority regarding hydrography and nautical charting.

Source

https://unstats.un.org/unsd/geoinfo/ungegn/docs/Training/Manila/2_Special_aspects_of_underwater_topography_naming.pdf

https://indianexpress.com/article/india/indian-ocean-structures-named-ashoka-chandragupt-kalpataru-9503174/

NCERT

PRACTICE QUESTION Q. What are the primary oceanic divisions, and how do they compare to the continents? 150 words