Oceans

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– 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 is a vast and mysterious place, covering over 70% of the Earth’s surface. It is home to a wide variety of life, from tiny plankton to giant whales. The ocean also plays a vital role in regulating the Earth’s Climate.

Ocean currents are large-scale movements of water in the ocean. They are caused by the Earth’s rotation, the sun’s heat, and the wind. Ocean currents transport heat and nutrients around the globe, and they play a major role in shaping the Earth’s climate.

The ocean floor is the surface of the ocean below the water. It is made up of a variety of features, including mountains, valleys, and trenches. The ocean floor is home to a wide variety of life, including fish, coral, and sponges.

Ocean life is the variety of Plants and animals that live in the ocean. It includes everything from tiny plankton to giant whales. Ocean life is essential to the Health of the ocean, and it provides us with food, medicine, and other Resources.

Ocean pollution is the contamination of the ocean by human activity. It can be caused by oil spills, sewage, and other pollutants. Ocean pollution can harm marine life, and it can also make the ocean unsafe for swimming and fishing.

Ocean resources are the Natural Resources that are found in the ocean. They include oil, gas, Minerals, and fish. Ocean resources are important to the global economy, and they are also essential to the health of the ocean.

Ocean waves are the rise and fall of the ocean surface. They are caused by the wind, and they can be very powerful. Ocean waves can cause damage to coastal Infrastructure-2/”>INFRASTRUCTURE, and they can also be dangerous to swimmers and surfers.

Oceanography is the study of the ocean. It is a multidisciplinary field that includes physics, chemistry, biology, and geology. Oceanography is important for understanding the ocean, and it is also important for managing the ocean’s resources.

Tides are the rise and fall of the ocean’s surface caused by the gravitational pull of the moon and the sun. Tides are important for navigation, and they can also be used to generate electricity.

The water cycle is the continuous movement of water on, above, and below the Earth’s surface. It is powered by the sun’s energy, and it is essential for life on Earth. The water cycle is a complex system, and it is important to understand how it works in order to protect our planet.

The ocean is a vital part of our planet, and it is important to protect it. We can do this by reducing pollution, conserving resources, and managing the ocean sustainably.

Here are some frequently asked questions and short answers about the topic of “Oceans” without mentioning the topic:

What is the largest ocean?
The Pacific Ocean is the largest ocean in the world, covering an area of 165,250,000 square kilometers (63,800,000 square miles).
What is the deepest ocean?
The Pacific Ocean is the deepest ocean in the world, with an average depth of 4,000 meters (13,100 feet).
What is the coldest ocean?
The Arctic Ocean is the coldest ocean in the world, with an average surface temperature of -1.8 degrees Celsius (28.8 degrees Fahrenheit).
What is the saltiest ocean?
The Atlantic Ocean is the saltiest ocean in the world, with an average salinity of 35 parts per thousand.
What is the most polluted ocean?
The Pacific Ocean is the most polluted ocean in the world, with an estimated 8 million tons of plastic waste entering the ocean each year.
What is the most biodiverse ocean?
The Pacific Ocean is the most biodiverse ocean in the world, with an estimated 230,000 species of marine life.
What is the most important ocean?
All of the oceans are important, but the Pacific Ocean is particularly important because it is the largest ocean and it contains the largest amount of marine life.
What are the threats to the oceans?
The oceans are facing a number of threats, including Climate Change, pollution, and overfishing.
What can we do to protect the oceans?
We can protect the oceans by reducing our carbon emissions, reducing pollution, and sustainably managing fisheries.

The Earth’s Atmosphere is made up of:
(A) Nitrogen and Oxygen
(B) Nitrogen, oxygen, and argon
(C) Nitrogen, oxygen, argon, and carbon dioxide
(D) Nitrogen, oxygen, argon, carbon dioxide, and water vapor
The Earth’s atmosphere is divided into four layers:
(A) Troposphere, Stratosphere, Mesosphere, and Thermosphere
(B) Troposphere, stratosphere, mesosphere, and exosphere
(C) Troposphere, stratosphere, mesosphere, thermosphere, and ionosphere
(D) Troposphere, stratosphere, mesosphere, thermosphere, ionosphere, and exosphere
The Earth’s atmosphere is important for life because it:
(A) Provides oxygen for Respiration
(B) Protects us from harmful radiation
(C) Regulates the Earth’s temperature
(D) All of the above
The Earth’s climate is changing because of:
(A) Human activity
(B) Natural causes
(C) Both human activity and natural causes
(D) None of the above
The Greenhouse Effect is caused by:
(A) Greenhouse gases
(B) Clouds
(C) Both greenhouse gases and clouds
(D) None of the above
The main greenhouse gases are:
(A) Water vapor, carbon dioxide, methane, and nitrous oxide
(B) Carbon dioxide, methane, nitrous oxide, and ozone
(C) Water vapor, carbon dioxide, methane, nitrous oxide, and ozone, and chlorofluorocarbons
(D) Water vapor, carbon dioxide, methane, nitrous oxide, ozone, chlorofluorocarbons, and Hydrofluorocarbons
The effects of climate change include:
(A) Rising sea levels
(B) More extreme weather events
(C) Changes in plant and animal life
(D) All of the above
We can reduce our impact on climate change by:
(A) Reducing our emissions of greenhouse gases
(B) Conserving energy
(C) Using RENEWABLE ENERGY sources
(D) All of the above
The ozone layer is a region of Earth’s stratosphere that absorbs most of the Sun’s ultraviolet radiation.
(A) True
(B) False
The ozone layer is important because it protects life on Earth from harmful ultraviolet radiation.
(A) True
(B) False