Oceans - Bottom Relief

Oceans – Bottom Relief

Four major divisions can easily be identified on the ocean floor:

The continental shelf,
the continental slope,
the continental rise,
the abyssal plain.

Besides these, there are many associated features—ridges, hills, seamounts, guyots, trenches, canyons, sleeps, fracture zones, island arcs, atolls, coral reefs, submerged Volcanoes-2/”>Volcanoes and sea-scarps.

This great variety of relief is largely due to interaction of tectonic, volcanic, erosional and depositional processes. At greater depths, the tectonic and volcanic phenomena are more significant processes.

Continental Shelf: This is a gentle seaward sloping surface extending from the coasts toward s the open sea. In all, about 7.5% of the total area of the oceans is covered by the continental shelves. The shelf is formed by the drowning of a part of a continent with a relative rise in sea level or marine deposition beneath the water.

The Average width of the continental shelf is about 70 km and mean slope is less than one degree, but the width shows great variety from location to location. For instance, it is almost absent in the eastern Pacific, especially off South America and is upto 120 km wide along the eastern coast of USA. The seaward edge of the shelf is usually 150-200 metres deep.

The continental shelves are mostly covered by sediments of terrestrial origin. There are various types of shelves—glaciated shelf, coral reef shelf, shelf of a large river, shelf with dendritic valleys and the shelf along young mountain ranges.

Continental Slope

As the continental shelf nears its seaward edge, the gradient becomes steeper—two to five degrees. This is the site of the continental slope which descends to a depth of 3,500 metres and joins the shelf to the deep ocean floor. The site of the slope also indicates the end of the continental block. The slopes may be furrowed by canyons and trenches. Continental Rise

The continental slope gradually loses its steepness with depth. When the slope reaches a level of between 0.5° and 1°, it is referred to as the continental rise. With increasing depth the rise becomes virtually flat and merges with the abyssal plain.

Abyssal plains

Beyond the continental rise, at depths from 3,000 m to 6,000 m, lie the deep sea plains, called abyssal plains or abyssal floors. Covering nearly 40% of the ocean floor, the abyssal plains are present in all major oceans and several seas of the world. They are uniquely flat with a gradient of less than 10,000. The large supply of terrigenous and shallow water sediments buries the irregular topography to form a generally flat relief.

Submarine Ridges

Submarine ridges are mountain ranges, a few hundred kilometres wide and hundreds and often thousands of kilometres in length on the floors of oceans. Running for a total length of 75,000 km, these ridges form the largest mountain systems on earth.

These ridges are either broad, like a plateau, gently sloping or in the form of steep-sided narrow Mountains. These oceanic ridge systems are of tectonic origin and provide evidence in support of the theory of Plate tectonics.

Abyssal Hills

These are elevated features of volcanic origin. A submarine mountain or peak rising more than 1,000 metres above the ocean floor is known as a seamount. The flat topped mountains are known as guyots.

Seamounts and guyots are very common in the Pacific Ocean where they are estimated to number around 10,000.

Submarine Trenches or Deeps: These are the deepest parts of the oceans with their bottoms far below the average level of the ocean floors. A trench is a long, narrow and steep-sided depression on the ocean bottom, which is usually 5,500 metres in depth. The trenches lie along the fringes of the deep-sea plain and run parallel to the bordering Fold Mountains or the island chains.

They are believed to have resulted from down faulting or down folding of the earth’s crust and are, therefore, of tectonic origin. The trenches are very common in the Pacific Ocean and form an almost continuous ring along the western and eastern margins of the Pacific. The Mariana Trench off the Guam Islands in the Pacific Ocean is the deepest trench with a depth of more than 11 kilometres.

Submarine Canyons

These are steep valleys, forming deep gorges on the ocean floor. They are mainly restricted to the continental shelf, slope and rise. Broadly, there are three types of submarine canyons:

Small gorges which begin at the edge of the continental shelf and extend down the slope to very great depths, e.g., Oceanographer Canyons near New England.
Those which begin at the mouth of a river and extend over the shelf, such as the Zaire, the Mississippi and the Indus canyons.
Those which have a dendritic appearance and are deeply cut into the edge of the shelf and the slope, like the canyons off the coast of southern California. The Hudson Canyon is the best known canyon in the world. The largest canyons in the world occur in the Bering Sea off Alaska. They are the Bering, Pribilof and Zhemchung canyons.

Bank, Shoal and Reef

These marine features are formed as a result of erosional, depositional and biological activity. Also, these are produced upon features of diastrophic origin. Therefore, they are located on upper parts of elevations.

A bank is a flat topped elevation located in the continental margins. The depth of water here is shallow but enough for navigational purposes. The Dogger Bank in the North Sea and Grand Bank in the north-western Atlantic off Newfoundland are famous examples. The banks are sites of some of the most productive Fisheries-2/”>Fisheries of the world.

A shoal is a detached elevation with shallow depths, since they project out of water with moderate heights, they are dangerous for navigation.

A reef is a predominantly organic deposit made by living or dead organisms that forms a mound or rocky elevation like a ridge. Coral reefs are a characteristic feature of the Pacific Ocean where they are associated with seamounts and guyots. The largest reef in the world is found off the Queensland coast of Australia . Since the reefs may extend above the surface, they are generality dangerous for navigation.,

The ocean floor is a vast and varied landscape, with features ranging from towering mountains to deep trenches. The following are some of the most common features of the ocean floor:

Abyssal plains: Abyssal plains are the flattest and most extensive features on the ocean floor. They cover about 50% of the Earth’s surface and are typically found at depths of 3,000 to 6,000 meters. Abyssal plains are formed by the accumulation of sediment from the continents and from the remains of Marine Organisms.
Continental shelf: The continental shelf is the gently sloping edge of a continent that extends out into the ocean. It is typically found at depths of less than 200 meters. The continental shelf is important for a variety of reasons, including its role in fisheries, oil and gas exploration, and coastal protection.
Continental slope: The continental slope is the steeply sloping edge of the continental shelf that descends into the deep ocean. It is typically found at depths of 200 to 2,000 meters. The continental slope is important for a variety of reasons, including its role in submarine canyons, deep-sea currents, and the formation of oil and gas deposits.
Deep-sea fan: A deep-sea fan is a fan-shaped deposit of sediment that forms at the mouth of a submarine canyon. Deep-sea fans are typically found at depths of 2,000 to 6,000 meters. They are formed by the deposition of sediment from rivers, Glaciers, and other sources.
Guyot: A guyot is a flat-topped seamount that rises abruptly from the deep ocean floor. Guyots are typically found at depths of 1,000 to 4,000 meters. They are formed when volcanoes erupt on the ocean floor and then subside.
Mid-ocean ridge: A mid-ocean ridge is a long, continuous mountain range that forms the boundary between two tectonic plates. Mid-ocean ridges are typically found at depths of 2,000 to 4,000 meters. They are formed by the upwelling of magma from the Earth’s mantle.
Oceanic plateau: An oceanic plateau is a large, flat-topped area of the ocean floor that rises sharply from the surrounding abyssal plain. Oceanic plateaus are typically found at depths of 1,000 to 4,000 meters. They are formed by the upwelling of magma from the Earth’s mantle.
Trench: A trench is a long, narrow, deep depression in the ocean floor. Trenches are typically found at depths of 6,000 to 11,000 meters. They are formed by the subduction of one tectonic plate beneath another.
Seamount: A seamount is a submarine mountain that rises at least 1,000 meters above the surrounding seafloor. Seamounts are typically found at depths of 1,000 to 4,000 meters. They are formed by the upwelling of magma from the Earth’s mantle.

The ocean floor is a dynamic and ever-changing Environment. The features of the ocean floor are constantly being shaped by the forces of plate tectonics, erosion, and sedimentation. The ocean floor is also home to a wide variety of marine life, including fish, coral reefs, and whales.

What is the bottom relief of the ocean?

The bottom relief of the ocean is the shape of the ocean floor. It is made up of a variety of features, including mountains, valleys, and plains.

What are the different types of bottom relief in the ocean?

The different types of bottom relief in the ocean include:

Abyssal plains: These are flat, featureless areas that cover about 50% of the ocean floor.
Continental shelves: These are the shallow areas of the ocean that extend from the continents.
Continental slopes: These are the steep slopes that lead from the continental shelves to the abyssal plains.
Mid-ocean ridges: These are long, mountain ranges that run through the middle of the ocean.
Trenches: These are deep, narrow valleys that are found in some parts of the ocean.

What are the causes of the different types of bottom relief in the ocean?

The causes of the different types of bottom relief in the ocean include:

Plate tectonics: This is the theory that the Earth’s surface is made up of a number of plates that are constantly moving. The movement of these plates causes the formation of mountains, valleys, and other features on the ocean floor.
Sedimentation: This is the process by which material is deposited on the ocean floor. Sediment can be carried to the ocean by rivers, glaciers, and wind. It can also be formed by the remains of marine organisms.
Volcanic activity: This is the process by which volcanoes erupt on the ocean floor. Volcanic activity can cause the formation of mountains, islands, and other features on the ocean floor.

What are the effects of the different types of bottom relief in the ocean?

The effects of the different types of bottom relief in the ocean include:

The distribution of marine life: The type of bottom relief in an area can affect the distribution of marine life. For example, abyssal plains are home to a different type of marine life than continental shelves.
The formation of currents: The bottom relief of the ocean can affect the formation of currents. For example, mid-ocean ridges can cause the formation of upwelling currents.
The formation of waves: The bottom relief of the ocean can affect the Formation of Waves. For example, continental shelves can cause waves to break.

What are the challenges of studying the bottom relief of the ocean?

The challenges of studying the bottom relief of the ocean include:

The vastness of the ocean: The ocean is a very large area, and it is difficult to study all of it.
The depth of the ocean: The ocean is very deep, and it is difficult to study the bottom of the ocean.
The remoteness of the ocean: The ocean is a very remote place, and it is difficult to access many parts of it.
The harsh conditions of the ocean: The ocean is a very harsh environment, and it is difficult to study the bottom of the ocean in these conditions.

The deepest part of the ocean is called the:
(A) Mariana Trench
(B) Challenger Deep
(C) Pacific Ocean
(D) Atlantic Ocean
The ocean covers about:
(A) 71% of the Earth’s surface
(B) 60% of the Earth’s surface
(C) 50% of the Earth’s surface
(D) 40% of the Earth’s surface
The ocean is home to about:
(A) 2 million species of Plants and animals
(B) 1 million species of plants and animals
(C) 500,000 species of plants and animals
(D) 100,000 species of plants and animals
The ocean is a major source of:
(A) food
(B) Oxygen
(C) water
(D) all of the above
The ocean is a major factor in the Earth’s Climate.
(A) True
(B) False
The ocean is a major Source Of Energy.
(A) True
(B) False
The ocean is a major source of recreation.
(A) True
(B) False
The ocean is a major source of pollution.
(A) True
(B) False
The ocean is a major source of Biodiversity-2/”>Biodiversity.
(A) True
(B) False
The ocean is a major source of mystery.
(A) True
(B) False