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Ocean Floor Configuration: Relief Characteristics & Plate Tectonics| UPSC Notes
IMPORTANT LINKS
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GS Paper |
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Topics for UPSC Prelims |
Differences between passive and active continental margins, Mid-Atlantic Ridge, Mariana Trench, Hydrothermal Vents, Oceanic Fracture Zones, Transform Faults, Bathymetric Charts |
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Topics for UPSC Mains |
Seafloor Spreading and Plate Tectonics, Deep-Sea Trenches and Subduction Zones, Marine Resources and Biodiversity, Geopolitical Importance of Oceanic Features, deep-sea mining |
About the Ocean Floor
Oceans and seas are the most beautiful natural features of the planet Earth. The oceans are vast water bodies of saline water occupying the great depressions on the planet. They belong to the hydrosphere and they almost cover 97% of it. The water bodies like oceans cover 361 million sq.km of the earth’s surface. The volume of water is around 1.37 billion cubic km. They are very extensive and exhaustive and exploitable marine ecosystems. Very large masses of water with different dimensions exist as oceans. On-shore and off-shore marine which we have already learnt in previous junior classes, ecosystems are characterized by distinct features with unique flora and fauna. They generally hold many marine habitats and they also contain a lot of natural resources. When we move towards the seashore we may see the beaches with the tides splashing and waves that are dancing. There is a bluish body seen as a straight flat plane denoting the level of sea. The waves which are coming towards the land break while nearing towards the coast and subsidies that are touching the beach. The coastline that is discussed is said to be the boundary between ocean and land. The surface beneath the water that is oceanic is characterized by a lot of relief features. The configuration of the structure and relief features of the oceans also vary from each other.
Check out NCERT notes on the rock cycle here.
Geography of the Ocean Floor
Apart from the major divisions, the ocean floors have major and minor relief characteristics such as Continental Shelf, Ridges, Hills, Seamounts, Guyots, Trenches, Canyons, etc.
Major Relief Characteristics
The major relief characteristics of oceans include continental shelves, continental slopes, abyssal plains, mid-ocean ridges, and oceanic trenches.
Continental Shelf
A continental shelf is a section of a continent that is submerged beneath a shelf sea, which is a relatively shallow body of water. During glacial eras, sea level reductions exposed several of these shelves. An insular shelf is the shelf that surrounds an island.
Between the continental shelf and the abyssal plain, the continental margin consists of a steep continental slope surrounded by a flatter continental rise, where sediment from the continent above cascades down the slope and collects as a pile of sediment at the bottom.
The continental shelf is the stretch of land between continents that is populated by gulfs and seas that are relatively shallow. It is the ocean’s shallowest point. The shelf generally comes to a halt at an extremely steep slope known as the shelf break.
Continental shelves have an average breadth of 80 kilometers Along some margins, as on the Chilean coasts, continental shelves are very narrow or non-existent. The Arctic Ocean’s Siberian shelf is the world’s largest.
Massive sedimentary deposits, which the continental shelves have accumulated over time, have turned out to be a source of fossil fuels.
Continental Slope
A continental shelf is a section of a continent that is submerged beneath a shelf sea, which is a relatively shallow body of water. During glacial eras, sea level reductions exposed several of these shelves.
An insular shelf is the shelf that surrounds an island. Between the continental shelf and the abyssal plain, the continental margin consists of a steep continental slope surrounded by a flatter continental rise, where sediment from the continent above cascades down the slope and collects as a pile of sediment at the bottom.
The continental slope connects the ocean basins to the continental shelf. It begins where the continental shelf’s bottom rapidly drops off onto a steep slope. This area contains canyons and ditches.
Check out these NCERT Notes on Endogenic Processes here.
Deep Sea Plain
Deep sea plain is also known as Abyssal Plain, and it’s an underwater plain on the deep ocean floor that’s often found between 3,000 and 6,000 meters deep.
Abyssal plains cover more than half of the Earth’s surface, lying between the foot of a continental rise and a mid-ocean ridge. They are one of the world’s flattest, smoothest, and least explored places.
Abyssal plains are important geologic features in ocean basins (the other elements being an elevated mid-ocean ridge and flanking abyssal hills). The abyssal plain was formed by the spreading of the seafloor (plate tectonics) and the melting of the lower oceanic crust.
The deep-sea plain is characterized by gently sloping sections. These are the flattest and flattest places on the planet. Fine-grained sediments such as silt and clay cover the plains entirely.
Oceanic Deeps or Trenches
Long, narrow topographic depressions on the ocean floor are known as oceanic trenches. They’re usually 50 to 100 kilometers broad and 3 to 4 kilometers below the surrounding marine floor, but they can stretch for thousands of kilometers.
Around 50,000 kilometers of oceanic trenches exist around the world, predominantly in the Pacific Ocean, but also in the eastern Indian Ocean and a few other places.
The deepest sections of the waters are known as trenches. The trenches have narrow basins and are relatively steep-sided. They’re 3-5 kilometers below the surface of the ocean. They can be found in the bottoms of continental slopes and along the arcs of island chains. Active volcanoes and powerful earthquakes are linked to trenches. As a result, they are critical in the study of plate movements.
Know more about NCERT Notes on Salinity of Ocean Water here.
Minor Relief Characteristics
The ocean floor features minor relief characteristics, including abyssal plains, seamounts, guyots, mid-ocean ridges, trenches, and hydrothermal vents.
- Abyssal plains are flat and featureless regions found in the deep ocean basins.
- Seamounts are underwater mountains formed by volcanic activity.
- Guyots are flattened seamounts that have eroded over time.
- Mid-ocean ridges are underwater mountain ranges where tectonic plates spread apart. This results in the upwelling of magma and the creation of a new crust.
- Trenches are deep, elongated depressions formed at subduction zones where one tectonic plate is forced beneath another.
- Hydrothermal vents are openings in the ocean floor where superheated fluid rich in minerals is expelled, supporting unique ecosystems.
You might like to read: Earth – Origin and Evolution NCERT notes!
Ocean Floor and Plate Tectonics
The plates of Indian or India Plate is a minor tectonic plate straddling the Equator in the Eastern Hemisphere. Originally we can say that it is a part of the ancient continent of Gondwana. From which India broke away from the other fragments of Gondwana 100 million years ago and began moving north. Once this fused with the adjacent Australia to form a single plate of Indo-Australian and recent studies suggest that Australia and India have been separate plates for at least 3 million years and likely longer. The plate of India includes most of South Asia that is the Indian subcontinent and a portion of the basin that is under the Indian Ocean including parts of South China and western Indonesia as well. And extending up to but not including Ladakh, Balochistan and Kohistan.
Know more about the Factors Controlling Temperature Distribution here.
Distribution of Volcanoes and Earthquakes
The maps study is showing that the distribution of seismic activity and volcanoes is discussed from a very early time. We will notice that a line of dots in the central parts of the ocean of the Atlantic is almost parallel to the coastlines. It further extends and gets into the Indian Ocean. It bifurcates a little part of the south of the Indian subcontinent with one branch moving into the country of East Africa and the other meeting a similar line from Myanmar to New Guiana. We will even see that this line of dots coincides with the mid oceanic ridges. In general there is the focus of the earthquake in the areas of mid-oceanic ridges at the depth which are shallow whereas along the Alpine-Himalayan belt as well as the rim of the Pacific. The earthquakes are deep-seated in that region. The map of volcanoes which is designed also shows a similar pattern. The Pacific Ocean’s rim is also known as the rim of fire due to the existence of active volcanoes in this area.
You might also like to read NCERT notes on Volcanic Landforms!
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Ocean Floor and its Features UPSC FAQs
What is the ocean floor?
The ocean floor refers to the bottom surface of the world's oceans. This includes various geological formations and features beneath the water.
What are the main features of the deep sea floor?
The main features of the deep sea floor include abyssal plains, seamounts, trenches, mid-ocean ridges, and hydrothermal vents.
What are the most features of the ocean floor covered with?
The most features of the ocean floor are covered with sediment, which can include fine particles, clay, sand, and organic matter.
What is the most common feature found on the seafloor?
The most common feature found on the seafloor is the abyssal plain. It is a flat and relatively featureless region in the deep ocean basins.
What percent of earth’s surface does the ocean floor cover?
Our oceans cover more than 70 percent of the Earth's surface.