Mentors Comment:
- Provide a brief introduction about oceanic and continental relief.
- Discuss the reasons for formation of various oceanic reliefs.
- Discuss the significance of various oceanic reliefs.
Answer:
The lithosphere (crust and upper mantle) has two broad relief features — continents and ocean basins, which are created by the movement of plates along plate-tectonic boundaries, and consequential volcanic and depositional processes. The relief features of continents may be seen to consist of active mountain- making belts (narrow zones along the margins of lithospheric plates, like the Alps and Himalayas) and inactive regions of old, stable rock (continental shields and mountain roots).
Oceans have a more diverse relief than the continents. Much of the oceanic crust is less than 60 million years old, while the great bulk of the continental crust is over 1 billion years old. The floors of the oceans are rugged with the world’s largest mountain ranges, deepest trenches and largest plains. It is classified into major and minor relief features. Continental shelf, continental slope, oceanic deeps and deep sea plain are major while hills, sea mounts, guyots, trenches and canyons are minor.
Formation of main relief features of the Ocean and their significance
Continental margin: it is subdivided into continental shelf and continental slope, with the former simply being a submerged part of the continent. Passive continental margins such as most of the Atlantic coasts have wide and shallow shelves, made of thick sedimentary wedges derived from long erosion of a neighboring continent. Active continental margins have narrow, relatively steep shelves, due to frequent earthquakes that move sediment to the deep sea. Continental shelves are a rich source of Petroleum reserves e.g. Bombay High, Persian Gulf. Other resources available in shelves are sulphur, monazite sand, calcium and pearls. Presence of ample sunlight, optimum depth and nutrients deposited from rivers and waves make them flourishing habitat for organisms. Thus they are potential fishing grounds.
Submarine Canyons – It is another prominent feature which is cut into continental slope and usually found near the mouth of rivers. It is formed due to erosion of continental slope by turbidity currents or mass wasting. They act as preferential particle-transport routes from coastal zone down continental slopes to deep seafloor, enhance carbon sequestration, provide nursery and refuge sites for marine life and they can also be a rich source of genetic resources and chemical compounds.
Deep sea plains – It consists older parts of oceanic crust that are smoothened due to sediment deposition. It has deposits from continents (terrigenous), marine life (biogenous) and salts and mineral (inorganic). Abyssal plains of Southern Indian Ocean and Eastern Pacific Ocean are rich sources of Poly Metallic Nodules.
Mid-Oceanic ridge – These are the youngest portions of the ocean basins where new ocean crust is generated through mantle upwelling and plate divergence. Similarity of constituents, age and magnetic properties of rocks on either side of the ridge helped in understanding sea-floor spreading. Water from hydrothermal vents (along the mid-ocean ridges) is rich in dissolved minerals and supports organisms like chemoautotrophic bacteria.
Oceanic deeps – These are the deepest parts of ocean basins formed due to subduction of oceanic crust under continental crust. These play significant role in the study of plate movements.
Seamounts/Guyots – these are submarine volcanic cones. Seamounts and the water column above them serve as important habitats, feeding grounds and sites of reproduction for many open-ocean and deep-sea species.
Comments
19 responses to “The mapping of ocean floor reveals complex and varied features, which rival the relief features on land. Discuss the reasons for the formation of main relief features of ocean along with their significance. (150 words)”
Until early 20th century, the ocean was thought to be a PLAIN Sea floor with no Relief structures. It was only during World War 2 when we got to know that, like land, ocean floor too has amazing relief features which are complex & varied and rival the land reliefs.
The geographers started mapping ocean floor to know about the hidden wonder underneath & the following things were found..
1. Canyons: like canyons on land, canyons in ocean are present which are formed due to breakage of sea floor.
2. Ocean ridges: when two ocean floors diverge, non dense lava erupts & forms mountains. These are different from land mountains as they do not grow very high.
3. Island: when two ocean floors converge, the thick lava forms initial islands which may emerge later as islands on the top of ocean (not all do so)
4. Sea mounts & guyots: these are ocean mountains. If it has flat top, it is a guyot & if it has tipped top, it is a sea mount.
5. Hot spots on ocean sea floor causes islands. These may submerge once the ocean plate above the hot spot drifts away.
6. Abyssal plain: deep empty plain just like plains on land.
According to scientists, only 5% of the total ocean floor was actually mapped. We do not know what other features we encounter in the future but the present relief on ocean are as complex & varied as on land.
Significance:
1. Study of earth: the different formations on ocean can be very useful for geographers, Oceanogeaphers, geologists to understand how earth works & it’s formation
2. Minerals: the underground mountains, ocean beds are significant in their mineral wealth, especially poly metallic modukes.
3. Research: the rich features on ocean floor can be used for scientific research & technology which may open a Pandora box of secrets unknown to us.
Conclusion:
Oceans, which cover around 70% of earth is not yet fully mapped. Mapping of entire ocean floor will not only reveal it’s complex features but also reveal it’s unknown features which can not only rival the land but might triumph land with it’s relief resources.
Hi Ruthvik
Please try to write on paper. That will give you better understanding of how to use space properly.
Points are in right direction.
You failed to discuss one aspect of the question in detail: “Discuss the reasons for the formation of main relief features of ocean”
Apart from that answer is fine.
Oh…. I did miss that point in question (i.e. Formation of relief).. & I’m not finding upload button of files on my comment… So, directly typed in comment..
Answer is in this link
https://photos.app.goo.gl/RgATvwHLLMVkGXS7A
Not checked
Please upload the answer on the platform and not on the third party websites
MOJO9615J00A46183569
Hi Mohsin
You have covered all the major aspects of the topic.
Good use of diagram
Structure is well placed.
q1
MOJO9708E00A65259027
Good use of diagram.
The first part of the answer is good and explanation is OK.
But the second part, where you discussed the significance of these features need more content and depth.
Apart from that, good discussion.
Q1
Hi Avani
Good intro but structure can be made better there. Do not break the flow of intro.
Very detailed diagram. Keep it up.
Answer has decent approach of discussing each features with details.
But the main body, towards the end looks as if it ended abruptly.
In some parts, you failed to discuss the reasons for the formation of those features.
Good conclusion
Q1. MOJO9710800D30462641
Hi Shivangi
Good diagram. But try to bring it in after your intro. That will make it more relevant.
The discussion for significance of these features should have proper sub heading.
Rest of the answer is fine.
Good presentation and explanation.
Q1
Hi Mud Borne.
Answer is uni dimensional.
It doesn’t cover 2nd part of the question where you had to discuss the significance.
Also you have to mention various features after your intro. Give details about them.
Answer lacks depth.
Good diagram.
Take your space and do not let it go waste. You have 3 pages to attempt these questions so utilise each and every bit.
MOJO9616700A12539386
Sir please review
please review .