33. Indian-World Geography[Oceanology][Major and Minor Ocean Relief Features-1][Part-33][09-12-2024]

Contents :
-Ocean Relief : Relief features formed in the ocean, due to tectonic, volcanic, erosional and depositional processes and their interactions.
-There are classified into two categories :
1. Major Oceanic Features
-The Continental Shelf
-The Continental Slope
-The Continental Rise
-The Deep Sea Plain or the Abyssal Plain
2. Minor Oceanic Features
-Ridges, Hills, Seamounts, Guyots, Trenches, Canyons, Sleeps, Fracture Zones, Island Arcs, Atolls, Coral Reefs, Submerged Volcanoes, and Sea-Scraps
1.Major Oceanic Features :
-The Continental Shelf :
-Gentle Sloping Sea Ward Extension of the Continental Plates
-Occupied by relatively shallow seas and gulfs
-Covers 7.5% of the total area of the oceans
-Gradient or Slope : Less than or equal to 1°
-Width : Can be wide around 1500 kms -Siberian Shelf (Arctic Ocean) and can be narrow around 120 kms-Coasts of Chile and Western Sumatra
-Depth : Can vary between 30m to 600m
-Breaks at a very steep slope called "Shelf Break"
-Shelves are covered with sediments brought by glaciers and rivers
-Serves as "sources of fossil fuels"
-Eg : Continental Shelf of South-East Asia, Great Banks around New Foundland, Submerged region between Australia and New Guinea
-Reasons for formation of shelves :
1.Submergence of part of a continent
2. Relative Rise in the Sea Level
3. Sedimentary deposits brought by rivers
-Types of Continental Shelves :
1.Glaciated Shelf : Greenland
2. Coral Reef Shelf : Queensland, Australia
3. Large River Shelf : Around-Nile Delta
4. Dendritic Valley Shelf : Mouth of the Hudson River, the USA
5. Young Mountain Ranges-Shelf : Shelves around the Hawaiian Islands
-Importance of Continental Shelves :
-Source of Marine Food
-Richest Fishing Grounds
-Potential Sites for Mineral : 20% petroleum and natural gas comes from the shelves, source of polymetallic nodules (Manganese nodules-Concentric layers of Iron and Manganese Oxides) and mineral ores like manganese, iron copper, gold etc.
-The Continental Slope :
-Connects the continental shelf and ocean basins
-Begins at a very steep slope called "Shelf Break"
-Gradient or Slope : Between 2° to 5°
-Depth : Can vary between 200m to 3000m
-The seaward edge of the continental slope loses gradient at this depth and gives rise to continental rise.
-The continental slope boundary indicates the end of the continents.
-Canyons and trenches are observed in this region.
-The Continental Rise :
-Gradually loses its steepness with depth
-Gradient or Slope : Between 0.5° to 1°
-With increasing depth the rise becomes virtually flat and merges with the abyssal plain
-Deep Sea Plain or Abyssal Plain :
-Gently sloping areas of the ocean basins
-Flattest and smoothest regions of the world because of terrigenous [denoting marine sediment eroded from the land] and shallow water sediments that buries the irregular topography.
-Covers : 40% of the Ocean Floor
-Depth : Can vary between 3000m to 6000m
-Covered with fine-grained sediments like clay and silt.