Unit - 4 (Oceanology)
- Distribution of Earth's Water
- Ocean bottom topography
- Temperature of the Oceans
- Salinity of the Oceans
- Oceanic deposits
- Coral reefs
- Ocean Currents & Circulations
- El Nino, La Nina, Madden Julian Oscillation (MJO) & Indian Ocean dipole
- Tides
Previous Unit - Climatology
Next Unit - Biogeology
Oceanography - It is the study of the various aspects related to Ocean and its water.
Distribution of Earth's Water
- Earth's Water -
- 97% - Saline (present in Oceans and Seas)
- 3% - Fresh Water
- Fresh Water -
- 68.7% - present in ice-caps and glaciers
- 30.1% - present as ground water
- 0.3% - present as surface water
- 0.9% - present in other forms (like moisture)
- Fresh Surface Water -
- 87% - Present in lakes
- 11% - Present in swamps
- 2% - Present in rivers
Ocean Bottom Topography
Ocean bottom topography includes -
- From continental side (Continental Crust which is submerged in the Ocean)
- Continental Self (major topography)
- Continental Slope (major topography)
- Continental Rise (minor topography)
- Oceanic Crust
- Abyssal Plain (minor topography)
- Sea Mount and Guyots (minor topography)
- Volcanic Islands (minor topography)
- Mid-Oceanic Ridges (major topography)
- Trenches (major topography)
Continental Shelf
- These are the submerged shallow portions of the continental crust.
- The depth is between 150 to 200 m.
- It is rich in Sun light and Oxygen which favours the growth of life (marine life).
- Continental shelfs are the regions of rich fishing grounds. Wider the continental shelf, better it was for fishing growth. For example - Grand bank of Newfoundland.
- Width of the shelf is dependent on the slope of adjacent land. It is wider along the coastal plains and narrower along the mountain coast.
- For example - The continental shelf along the West Coast of USA has less width because of the presence of Rockies than the width of continental shelf along the East Coast of USA where there is a plain land.
- Exception - In India, the western coast has wider continental shelf inspite of having Western Ghats. It is because the major portion of Western Ghats which was once above the sea level is now submerged.
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Continental Slope
- It is along the outer edge of the continent where it forms the boundary between the continents and oceans.
- It is much steeper in slope than the continental shelf.
Continental Rise
- It is located at the base of the continental slope which is less steeper than the continental slope.
- It continues into the Abyssal Plain.
- It is absent along the convergent plain boundary (Ocean-Continent Convergent) where we can find trenches.
Submarine Canyons (minor topography)
- These are the canyons formed along the continental slope and shelf because of the turbidity currents of rivers entering the oceans.
- These are formed due to the erosional effect of river water entering the oceans.
Abyssal Plain
- These are tectonically inactive ocean floor extending for a larger area with relatively smooth surface.
- It is made up of different oceanic sediments.
- It is also known as Ocean basin.
Sea Mount
- These are the isolated volcanic features along the oceanic floor and are formed due to volcanic activity along the hotspots.
Guyots
- Guyots are the flat topped Sea Mounts whereas Sea Mounts are sharply pointed.
- Guyots are flat topped hills with their summit below the water level.
- Guyots are the locations with good fishing bands and coral reefs.
Volcanic island
- Volcanic islands are the Sea Mounts which are having their peaks above the surface of water.
Island Arc
- It is a chain of volcanic islands generally convex towards the open ocean along the Ocean-Ocean Convergent boundary.
Mid-Oceanic Ridges
- They are formed due to the divergence of oceanic plates (Ocean-Ocean divergent plate boundary).
Trenches
- These are the deepest part of the oceanic basin.
- They are formed along the boundary of oceanic crust due to convergence.
Previous Article - Climatic Regions of the World
Next Article - Temperature of the Oceans
Notes on other subjects
Optional Notes
Note - This is my Vision IAS Notes (Vision IAS Class Notes) and Ashutosh Pandey Sir's Public Administration Class notes. I've also added some of the information on my own.
Hope! It will help you to achieve your dream of getting selected in Civil Services Examination 👍
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