The Ocean
You may know that the oceans cover about 70 percent of the Earth's surface, and that about 97 percent
of all water on and in the Earth is saline—there's a lot of salty water on our planet. By some estimates, if
the salt in the ocean could be removed and spread evenly over the Earth's land surface it would form a
layer more than 500 feet (166 meters) thick, about the height of a 40-story office building.
Where did all this salt come from?
Salt in the ocean comes from rocks on land.
The rain that falls on the land contains some dissolved carbon dioxide from the surrounding air. This
causes the rainwater to be slightly acidic due to carbonic acid. The rain physically erodes the rock and the
acids chemically break down the rocks and carries salts and minerals along in a dissolved state as ions.
The ions in the runoff are carried to the streams and rivers and then to the ocean. Many of the dissolved
ions are used by organisms in the ocean and are removed from the water. Others are not used up and
are left for long periods of time where their concentrations increase over time.
The two ions that are present most often in seawater are chloride and sodium. These two make up over
90% of all dissolved ions in seawater. The concentration of salt in seawater (salinity) is about 35 parts per
thousand. In other words, about 35 of 1,000 (3.5%) of the weight of seawater comes from the dissolved
salts; in a cubic mile of seawater the weight of the salt, as sodium chloride, would be about 120 million
tons. And, just so you don't think seawater is worthless, a cubic mile of it also can contain up to 25
pounds of gold (at a concentration of 0.000005 parts per million). Before you go out and try alchemy on
seawater, though, just think about how big a cubic mile is (1 cubic mile contains 1,101,117,147,000
gallons!).
Hydrothermal vents are recently-discovered features on the crest of oceanic ridges that contribute
dissolved minerals to the oceans. These vents are the exit point on the ocean floor from which sea water
that has seeped into the rocks of the oceanic crust has become hotter, has dissolved some of the
minerals from the crust, and then flows back into the ocean. With the hot water comes large amounts of
dissolved minerals. Estimates of the amount of hydrothermal fluids now flowing from these vents indicate
that the entire volume of the world's oceans could circulate through hydrothermal vent systems every
10-20 million years. Thus, this process has a very important effect on salinity. The reactions between
seawater and oceanic basalt, the rock of ocean crust, are not one-way, however; some of the dissolved
salts react with the rock and are removed from seawater.
A final process that provides salts to the oceans is submarine volcanism, the eruption of volcanoes
underwater. This is similar to the previous process in that seawater is reacting with hot rock and
dissolving some of the mineral constituents.
Salinity is the amount of salt in the ocean.
The salinity of an ocean depends on two factors.
1. How fast the water evaporates
2. The amount of water run off from the land around the ocean
How does salinity affect marine organisms?
An ocean’s salinity affects marine organisms and plants. Animals that live in salt water have developed
adaptations to survive in salty environments. Without salt water and dissolved gasses, these organisms
and plants would eventually die.
Humans cannot drink saline water. But, saline water can be made into freshwater. The process is called
desalination, and it is being used more and more around the world to provide people with needed
freshwater.
The huge body of salt water on the earth's surface is divided into five major oceans:
1.
2.
3.
4.
5.
Pacific Ocean
Atlantic Ocean
Arctic Ocean
Indian Ocean
Southern Ocean
The Pacific Ocean
The Pacific Ocean is the largest of the oceans covering around one third of the earth's surface. It is
around 15 times the size of the United States.
It separates Asia and Australia from North and South America.
With 25,000 islands in the region, the ocean also contains the most biodiverse waters in the world –
thanks to the Coral Triangle.
Deepest Point: Mariana Trench, 10,911 meters
Covers: 30.5% of Earth’s total surface area
Salt content is around 3.5%
Interesting facts:
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60% of the world’s fish come from The Pacific Ocean
The Pacific Ocean shrinks in size by just over two centimeters each year
The Pacific Ocean Basin is home to 75% of the world’s volcanoes
There are more than 25,000 islands in the Pacific
Pacific Ocean was declared “Mar Pacifico” in 1521 which is Portuguese for “Peaceful Sea”
The Atlantic Ocean
The Atlantic Ocean is the world's second largest ocean.
It is located between the continents of North and South America, and Europe and Africa.
Deepest Point: Puerto Rico Trench, 8,605 meters
Covers: 20.8% of Earth’s total surface area
It is the saltiest of the five oceans with a salt content around 3.7%.
Interesting facts:
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The name Atlantic comes from the Greek word Atlantikos which was known in the English
language at the time, as the Sea of Atlas.
It’s the world’s youngest ocean, formed long after the Pacific, Indian and Arctic Oceans of the
Triassic Period.
Home to the earth’s largest mountain range, The Mid Atlantic Ridge, which is 40,000 kilometers
long by 1,601 kilometers wide – dividing the ocean into two distinct east and west regions.
The Atlantic is famous for being the home of the legendary area known as the Bermuda Triangle,
an area renowned for the mysterious disappearance of several aircraft and ships.
Titanic is one of the most famous ships in the history of mankind. It was the state-of-the-art
passenger voyage ship of its time. Titanic is mostly known for its deadly disaster that happened
on 15 April 1912. On that day, the ship got an accident with an iceberg which resulted in the
death of 1,500 human lives. The accident occurred in the Atlantic Ocean during the Titanic’s
voyage from Southampton to New York City. The wreckage of the Titanic was first discovered in
1985 at a depth of 4 kilometers.
The Indian Ocean
The Indian Ocean is the third largest ocean in the world. It is the warmest ocean in the world.
It lies south of Asia and India, and separates East Africa from Australia. The southern border is wide open
and exchanges with the much colder Southern Ocean.
With relatively few islands, the continental shelf areas tend to be quite narrow and not many shallow seas
exist. Some of the major rivers flowing into the Indian Ocean include the Zambezi, Indus, and the
Ganges.
Deepest Point: Sunda Deep, 7,450 meters
Covers: 14.4% of Earth’s total surface area
Interesting facts:
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It is estimated that approximately 40% of the world’s oil comes from the Indian Ocean.
There was a discovery of a submerged continent in the Indian Ocean named the Kerguelen
Plateau, it is believed to be of volcanic origins.
The Ocean’s water evaporates at an abnormally high rate due to its temperature.
Every year it is estimated that the Indian Ocean becomes approximately 20 centimeters wider.
The Southern Ocean
The Southern Ocean is the fourth largest, or second smallest of the oceans.
It is located around the South Pole across the Antarctic circle in the Southern Hemisphere.
Compared to the other five oceans, the floor of the Southern Ocean is quite deep – ranging from 4,000 to
5,000 meters below sea level over most of the area that it occupies.
In September of each year, a mobile ice pack situated around the Antarctic reaches its greatest seasonal
extent covering around 19 million square kilometers– later in March the ice pack shrinks by almost 85%.
Deepest Point: South Sandwich Trench, 7,235 meters
Covers: 4.0% Earth’s total surface area
The salinity level of the Southern Ocean changes as you go away from Antarctica. It has been found that
salinity near the Antarctica land is decreasing due to the increased melting of glaciers over the past few
decades.
Interesting facts:
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The world’s largest penguin species, the emperor penguin, lives on the ice of the Southern Ocean
and on the Antarctica continent. Along with the world’s largest animal, the blue whale, who often
calls these waters home.
Antarctica is home to 90% of the world’s ice. This continent contained within the Southern
Ocean’s boundaries is the windiest, driest and coldest continent in the world.
The ocean is the youngest of the five oceans at only 30 million years of age and formed when the
continents of South America and Antarctica completely split apart.
Clouds are brighter in the Southern Ocean due to large plankton blooms, which release gasses
that allow water droplets to spread out more thus creating more reflective clouds.
The largest invertebrate, known as the colossal squid, lives in the Southern Ocean. They can
grow to a length of 14 meters. Also, the colossal squids have the largest eyes of any creature
which can grow to 27 centimeters in diameter.
Arctic Ocean
The Arctic Ocean is in the northern part of the earth, primarily around the North Pole. It is the
smallest and shallowest of the world's oceans.
The Arctic Ocean is the least saline ocean due to several reasons and its salinity also varies
significantly according to the season. The main cause of lower salinity is lower evaporation and a
high inflow of freshwater rivers from glaciers. The salinity becomes even lower in summer due to the
heavy melting of glaciers.
Deepest Point: Litke Deep in the Eurasian Basin, 5,450 meters
Covers: 2.8% of Earth’s total surface area
Interesting facts:
● There are four whale species in the Arctic Ocean including the bowhead whale, gray whale,
narwhal, and beluga whale.
● When the ice of the Arctic Ocean melts it releases nutrients and organisms into the water
which promotes the growth of algae. The algae feed zooplankton which serves as food for
sea life.
● Icebergs often form or break away from glaciers posing a threat to ships, the most famous
being the Titanic. Ships also often get trapped or crushed by the ice.
● Ice cover of the ocean is shrinking due to global warming, and it has been observed that the
rate of disappearance of ice cover is 3% per decade.
● B-15 Iceberg is the largest iceberg in the Arctic Ocean whose area is 11,000 sq. Km.
● The Arctic Ocean is governed by international law “The Law of the Sea Treaty” and is not
controlled by any one nation.
● Researchers believe that 25% of Earth’s crude oil reserves are buried under the Arctic
Ocean’s crust.