34. Indian-World Geography[Oceanology][Major and Minor Ocean Relief Features-2][Part-34][16-12-2024]

Content :
Minor Ocean Relief Features :
1.Oceanic Deep or Trenches :
-Steep Sided, Narrow Depressions
-Found in the deepest parts of the oceans
-Formed along convergence zones : Ocean-Continent or Continent-Continent
-Depth : 3-5 kms surrounding ocean floor
-Lie along fringes of the deep-sea plains at the base of the continental slopes and along island arcs
-Run parallel to the bordering fold mountains or the island chains
-Common in the Pacific Ocean
-Associated with active volcanoes and strong earthquakes
-Eg. Mariana Trench off the Guam Island [Depth-Around 11 Kms or above]
-Total : 57 trenches discovered so far [32 in the Pacific Ocean, 19 in the Atlantic Ocean and 6 in the Indian Ocean]
2.Mid-Oceanic or Sub-Marine Ridges :
-Composed of two chains of mountains separated by a large depression
-Peaks as high as 2,500 m and some even reach above the ocean’s surface
-Total Length : 75,000 km
-Formed along divergence zones : Ocean-Continent
-Forms the largest Mountain Systems on Earth.
-Ridges are either broad, like a plateau, gently sloping or in the form of steep-sided narrow mountains.
-Tectonic origin and provide evidence in support of the theory of Plate Tectonics.
-Eg. Iceland, a part of the mid-Atlantic Ridge
3.Abyssal Hills : Types-
Sea Mounts :
-Origin : Volcanic
-Height : 3000-4000 m
-Features : Pointed summits, rising from the sea floor, but doesnot reach the surface of the oceans
Guyots :
-Origin : Volcanic
-Height : Greater than 4000 m
-Features : Flat topped mountains and most of these features reach the surface of the oceans
4. Submarine Canyons
5. Atolls
-Low islands found in the tropical oceans
-May be a part of the sea (lagoon), or sometimes form enclosing a body of fresh, brackish, or highly saline water.
6. Reefs
-Predominantly organic deposit made by living or dead organisms that forms a mound or rocky elevation like a ridge.
-Characteristic feature of the Pacific Ocean
-Largest reef in the world is found off the Queensland coast of Australia.
-Reefs may extend above the surface, they are generally dangerous for navigation.