[Geography Notes] on Ocean Basin Pdf for Exam

Ocean basins can be defined as saucer-like depressions in the seabed of the earth’s surface. They differ in size from comparatively minor features of the continental margin to huge structural divisions of the deep sea basin. The largest ocean basins are about 3 to 5 kilometers deep and extend from the outer margins of the continents to the mid-ocean ridges.

Ocean basins cover about 71% of Earth’s surface or approximately 361 million square kilometers (140 million square miles). Their average depth is 16,000 feet, and the total volume is approximately 1.35 billion cubic kilometers (322 million cubic miles).

Divisions of the World Ocean

There are 5 major subdivisions of the world ocean. The five ocean basins are as follows:

1. The Pacific Ocean

2. Atlantic Ocean

3. Indian Ocean

4. Arctic Ocean

5. Southern Ocean

Pacific Ocean Basin

The Pacific Ocean contains more than half of its free water. In the area, this demonstrates about 155 million square kilometers. Comparatively, the area of Alaska, Hawaii, and the continental United States is about 4 million square miles, sixteen times less in surface area. All the continents could be accommodated into the Pacific basin.

The key characteristics of the oldest existing ocean basin have been shaped by the phenomena linked with plate tectonics. The coastal shelf that stretches to depths of about 600 feet, is narrow along North and South America, but is comparatively wide along Asia and Australia.

 

Under extreme pressure, the continental plates fold into mountain ranges and the oceanic plates are imposed downward, developing deep trenches known as subduction zones. The stresses at these regions of subduction are accountable for the volcanoes and earthquakes which give the Pacific basin the name “Ring of Fire.” 

Atlantic Ocean Basin

The second largest of Earth’s 5 oceans, the Atlantic Ocean is most massively travelled, and the most rigorously studied, primarily due to its significance in ship traffic between Europe and North America. This ocean’s name is extracted from Atlas, one of the Titans of Greek mythologies.

The Atlantic Ocean holds about 20% of Earth’s surface, demonstrating about 75 million square kilometers. This takes into account the marginal seas: the Black Sea, Baltic Sea, Caribbean Sea, Denmark Strait, and Davis Strait, part of the Drake Passage, Mediterranean Sea, North Sea, Norwegian Sea, Gulf of Mexico and almost all of the Scotia Sea.

The Atlantic Ocean basin formation happened during the Jurassic period, about 150 million years ago, when a rift opened up in the supercontinent of Gondwana, causing the separation of South America and Africa.

Indian Ocean Basin

The third largest of Earth’s five oceans, the Indian Ocean is bounded on the west by Africa, on the east by Australia, on the north by Asia and Australasian islands. It occupies a total area of 68 million square kilometers. No natural boundary separates the Indian Ocean from the Atlantic Ocean, but a line around 4,020 kilometers long, linking Cape Agulhas at the southern end of Africa with Antarctica, is usually considered to be the boundary.

Southern Ocean

Though not a true ocean basin, it stretches on the north from the coast of Antarctica to 60° South latitude that coincides with the Antarctic Treaty Limit. The Southern Ocean is now the fourth largest of the earth’s five oceans. The Southern Ocean consists of a special distinction of being a huge circumpolar body of water completely circumscribing the continent of Antarctica. It has an area of 20 million square kilometers and includes the Amundsen Sea, Bellingshausen Sea, Ross Sea, Weddell Sea a small part of the Scotia Sea, and part of the Drake Passage.

Arctic Ocean Basin

The smallest of Earth’s five ocean basins has a total surface area including major subdivisions— the Norwegian Sea, the North Sea, the North Polar Sea and the Barents Sea—is approximately 14 million square kilometers.

The average depth of the Arctic Ocean is about 4,900 feet while the deepest point in the Arctic Ocean is about 17,880 feet.

Fun Facts

• The ocean basins cover the largest area of the surface of the earth

• Due to plate tectonics, but most oceanic lithosphere finally is subducted. Hence, the only existing oceanic lithosphere is younger than Jurassic in age and happens at locations farthest from the oceanic spreading centers.

• Apart from areas where magmatism is strong enough to build volcanic structures above sea level, most of the oceanic magmatism are tough to access.