Ocean Facts





Oceans cover about 70% of the Earth's surface. The oceans contain roughly 97% of the Earth's water supply.

The oceans of Earth are unique in our Solar System. No other planet in our Solar System has liquid water (although recent finds on Mars indicate that Mars may have had some liquid water in the recent past). Life on Earth originated in the seas, and the oceans continue to be home to an incredibly diverse web of life.

The oceans of Earth serve many functions, especially affecting the weather and temperature. They moderate the Earth's temperature by absorbing incoming solar radiation (stored as heat energy). The always-moving ocean currents distribute this heat energy around the globe. This heats the land and air during winter and cools it during summer.

The Earth's oceans are all connected to one another. Until the year 2000, there were four recognized oceans: the Pacific, Atlantic, Indian, and Arctic. In the Spring of 2000, the International Hydrographic Organization delimited a new ocean, the Southern Ocean (it surrounds Antarctica and extends to 60 degrees latitude).

There are also many seas (smaller branches of an ocean); seas are often partly enclosed by land. The largest seas are the South China Sea, the Caribbean Sea, and the Mediterranean Sea.


Ocean Area (square miles) Average Depth (ft) Deepest depth (ft)
Pacific Ocean 64,186,000 15,215 Mariana Trench, 36,200 ft deep
Atlantic Ocean 33,420,000 12,881 Puerto Rico Trench, 28,231 ft deep
Indian Ocean 28,350,000 13,002 Java Trench, 25,344 ft deep
Southern Ocean 7,848,300 sq. miles (20.327 million sq km ) 13,100 - 16,400 ft deep (4,000 to 5,000 meters) the southern end of the South Sandwich Trench, 23,736 ft (7,235 m) deep
Arctic Ocean 5,106,000 3,953 Eurasia Basin, 17,881 ft deep

Why are the Oceans Salty?

As water flows in rivers, it picks up small amounts of mineral salts from the rocks and soil of the river beds. This very-slightly salty water flows into the oceans and seas. The water in the oceans only leaves by evaporating (and the freezing of polar ice), but the salt remains dissolved in the ocean - it does not evaporate. So the remaining water gets saltier and saltier as time passes.

Sea salts Parts per Thousand
chloride 19.3 o/oo
sodium 10.7 o/oo
sulfate 2.7 o/oo
magnesium 1.3 o/oo
calcium 0.4 o/oo
potassium 0.4 o/oo
bicarbonate 0.15 o/oo
bromide 0.07 o/oo
other 0.06 o/oo
Total Salinity 35.08 o/oo
The salinity (salt content) of ocean water varies. The oceans and seas contain roughly 5 x 10 16 tons of salts. One cubic foot of average sea water contains 2.2 pounds of salt.

The oceans are about 3.5% salt (by weight). Salinity is generally reported in terms of parts per thousand (abbreviated o/oo), the number of pounds of salt per 1,000 pounds of water; the average ocean salinity is 35 o/oo.

The saltiest water is in the Red Sea and in the Persian Gulf, which have a salinity of about 40 o/oo (due to very high evaporation rates and low fresh water influx). The least salty seas are in the polar regions, where both melting polar ice and a lot of rain dilute the salinity.

Sunlight is made up of all the colors of the rainbow: red, orange, yellow, green, blue, and violet. Some of the sunlight is reflected off the surface of the water, reflecting the color of the sky. Some of the sunlight penetrates the water and is scattered by ripples and particles in the water (this tinges the appearance of the ocean with the color of the particles). In deep water, much of the sunlight is scattered by the oxygen in the water, and this scatters more of the blue light.

Water absorbs more of the red light in sunlight; the water also enhances the scattering of blue light. Sir Chandrasekhar Venkata Raman (an Indian physicist) won the Nobel prize in 1930 for his work on light.

Some Oddly-Colored Seas:
The Red Sea often looks red because of red algae that live in this sea.
The Black Sea looks almost black because it has a high concentration of hydrogen sulfide (which appears black).


Did you know...?

Sharks attack some 50-75 people each year worldwide, with perhaps 8-12 fatalities, according to data compiled in the International Shark Attack File (ISAF). Although shark attacks get a lot of attention, this is far less than the number of people killed each year by elephants, bees, crocodiles, lightning or many other natural dangers. On the other side of the ledger, we kill somewhere between 20-100 million sharks every year through fishing activities.

Of the 350 or so shark species, about 80% grow to less than 1.6 m and are unable to hurt people or rarely encounter people. Only 32 species have been documented in attacks on humans, and an additional 36 species are considered potentially dangerous.

Almost any shark 1.8 m or longer is a potential danger, but three species have been identified repeatedly in attacks: the Great white, Tiger, and Bull sharks. All three are found worldwide, reach large sizes and eat large prey such as marine mammals or sea turtles. More attacks on swimmers, free divers, scuba divers, surfers and boats have been reported for the great white shark than for any other species. However, some 80% of all shark attacks probably occur in the tropics and subtropics, where other shark species dominate and Great white sharks are relatively rare.

An estimated 80% of all life on earth is found under the ocean surface and the oceans contain 99% of the living space on the planet. Less than 10% of that space has been explored by humans. 85% of the area and 90% of the volume constitute the dark, cold environment we call the deep sea. The average depth of the ocean is 3,795 m. The average height of the land is 840 m.

The oceans cover 71% of the Earth's surface and contain 97% of the Earth's water. Less than 1% is fresh water, and 2-3% is contained in glaciers and ice caps.

90% of all volcanic activity occurs in the oceans.

The speed of sound in water is 1,435 m/sec - nearly five times faster than the speed of sound in air.

The highest tides in the world are at the
Bay of Fundy, which separates New Brunswick from Nova Scotia. At some times of the year the difference between high and low tide is 16.3 m, taller than a three-story building.

Earth's longest mountain range is the Mid-Ocean Ridge more than 50,000 km in length, which winds around the globe from the Arctic Ocean to the Atlantic, skirting Africa, Asia and Australia, and crossing the Pacific to the west coast of North America. It is four times longer than the Andes, Rockies, and Himalayas combined.

The pressure at the deepest point in the ocean is more than 11,318 tons/sq m, or the equivalent of one person trying to support 50 jumbo jets.

The top ten feet of the ocean hold as much heat as the entire atmosphere.

The lowest known point on Earth, called the Challenger Deep, is 11,034 m deep, in the
Marianas Trench in the western Pacific. To get an idea of how deep that is, if you could take Mt. Everest and place it at the bottom of the trench there would still be over a mile of ocean above it. The Dead Sea is the Earth's lowest land point with an elevation of 396 m below sea level.

Undersea earthquakes, volcanoes and landslides can cause tsunamis (Japanese word meaning "harbor wave"), or seismic sea waves. The largest recorded tsunami measured 60 m above sea level caused by an 8.9 magnitude earthquake in the gulf of Alaska in 1899 traveling at hundreds of km/hr.

The average depth of the
Atlantic Ocean, with its adjacent seas, is 3,332 m; without them it is 3,926 m. The greatest depth, 8,381 m, is in the Puerto Rico Trench.

Pacific Ocean, the world's largest water body, occupies a third of the Earth's surface. The Pacific contains about 25,000 islands (more than the total number in the rest of the world's oceans combined), almost all of which are found south of the equator. The Pacific covers an area of 179.7 million sq km.

The Kuroshio Current, off the shores of
Japan, is the largest current. It can travel between 40-121 km/day at 1.6-4.8 kph, and extends some 1,006 m deep. The Gulf Stream is close to this current's speed. The Gulf Stream is a well known current of warm water in the Atlantic Ocean. At a speed of 97 km/day, the Gulf Stream moves a 100 times as much water as all the rivers on earth and flows at a rate 300 times faster than the Amazon, which is the world's largest river.

A given area in an ocean upwelling zone or deep estuary is as productive as the same area in rain forests, most crops and intensive agriculture. They all produce between 150-500 grams of Carbon per square meter per year.

The sea level has risen with an average of 10-25 cm over the past 100 years and scientists expect this rate to increase. Sea levels will continue rising even if the climate has stabilized, because the ocean reacts slowly to changes. 10,000 years ago the ocean level was about 110 m lower than it is now. If all the world's ice melted, the oceans would rise 66 m.

The density of sea water becomes more dense as it becomes colder, right down to its freezing point of -1.9C unlike fresh water which is most dense at 4C, well above its freezing point of 0C. The average temperature of all ocean water is about 3.5C.

Antarctica has as much ice as the Atlantic Ocean has water.

Arctic produces 10,000-50,000 icebergs annually. The amount produced in the Antarctic regions is inestimable. Icebergs normally have a four-year life-span; they begin entering shipping lanes after about three years.

Air pollution is responsible for 33% of the toxic contaminants that end up in oceans and coastal waters. About 44% of the toxic contaminants come from runoff via rivers and streams.

Each year, three times as much rubbish is dumped into the world's oceans as the weight of fish caught.

Oil is one of the ocean's greatest resources. Nearly one-third of the world's oil comes from offshore fields in our oceans. Areas most popular for oil drilling are the Arabian Gulf, the North Sea and the Gulf of Mexico.

Refined oil is also responsible for polluting the ocean. More oil reaches the oceans each year as a result of leaking automobiles and other non-point sources than the oil spilled in
Prince William Sound by the Exxon Valdez.

The record for the deepest free dive is held by Jacques Mayol. He dove to an astounding depth of 86 m without any breathing equipment.

A mouthful of seawater may contain millions of bacterial cells, hundreds of thousands of phytoplankton and tens of thousands of zooplankton.

The Great Barrier Reef, measuring 2,300 km in length covering an area more extensive than
Britain, is the largest living structure on Earth and can be seen from space. Its reefs are made up of 400 species of coral, supporting well over 2,000 different fish, 4,000 species of mollusc and countless other invertebrates. It should really be named 'Great Barrier of Reefs', as it is not one long solid structure but made up of nearly 3,000 individual reefs and 1,000 islands. Other huge barrier reefs include the barrier reefs of New Caledonia, the Mesoamerican (Belize) barrier reef, and the large barrier reefs of Fiji. The largest coral atoll complexes occur in the Maldive-Lakshadweep ecoregion of the central Indian Ocean and in Micronesia.

Fish supply the greatest percentage of the world's protein consumed by humans and most of the world's major fisheries are being fished at levels above their maximum sustainable yield; some regions are severely overfished.

More than 90% of the trade between countries is carried by ships and about half the communications between nations use underwater cables.

The swordfish and marlin are the fastest fish in the ocean reaching speeds up to 121 kph in quick bursts; the Bluefin Tuna (Thunnus thynnus) may reach sustained speeds up to 90 kph.

The Blue whale is the largest animal on our planet ever (exceeding the size of the greatest known dinosaurs) and has a heart is the size of a Volkswagen.

The Oarfish (Regalecus glesne), is the longest bony fish in the world. It has a snakelike body sporting a magnificent red fin along its 15.25 m length, a horselike face and blue gills, and accounts for many sea-serpent sightings.

Many fish can change sex during the course of their lives. Others, especially rare deep-sea fish, have both male and female sex organs.

One study of a deep-sea community revealed 898 species from more than 100 families and a dozen phyla in an area about half the size of a tennis court. More than half of these were new to science.

Life began in the seas 3.1 billion to 3.4 billion years ago. Land dwellers appeared 400 million years ago, relatively recently in geologic time.

Because the architecture and chemistry of coral is so similar to human bone, coral has been used to replace bone grafts in helping human bone to heal quickly and cleanly.

Deep Waters

The record for the deepest free dive is held by Jacques Mayol. He dove to an astounding depth of 282 feet without any breathing equipment.

The deepest spot on Earth, Challenger Deep, is 35,802 feet (11,034 m) deep. It is found in the Mariana Trench, one of the many deep valleys of the Pacific Ocean. The pressure here is over 8 tons per square inch.

Movie director James Cameron ventured to 12,378 feet below the surface of the Atlantic, in a submersible with a nine-inch-thick porthole, to film the movie "Titanic."


The highest tides on Earth are found in the Bay of Fundy east of New Brunswick, Canada. The channeling effect of the bay is responsible for the amazing difference between high tide and low tide, which, during spring tides, can reach 53.5 feet. This is almost as tall as a four-story building. Fishermen in Alma, New Brunswick have to adjust to the frequent changes.

Amazing Features of the Ocean Floor

The longest mountain range on Earth is really the Mid-Ocean Ridge. It extends from the Arctic Ocean, down the middle of the Atlantic, winding into the Pacific Ocean.

The largest waterfall on Earth is actually underwater. It is found in the Denmark Strait, and slowly cascades downward for 2.2 miles. This is over three times as tall as Angel Falls, in Venezuela, which is the tallest land waterfall.

The tallest mountain on Earth is also (you guessed it!) partly underwater. Mauna Kea, an inactive volcanic island in Hawaii, stands 33,465 feet tall when measured from ocean floor to summit.

Ocean Water

The elements oxygen and hydrogen are 96.5% of ocean water. The other 3.5% is dissolved elements, such as chlorine, sodium, and other salts.

About 97% of all of the Earth's water is saltwater.

The oceans cover about 71% of Earth's surface.

The thermocline is an ocean zone in which the temperature drops very rapidly. It is usually found at around 300 to 800 meters deep, between the relatively warm surface zone and the cold deep zone. The thermocline blocks sonar, so it is a favorite hiding place of submarines.

The temperature of most ocean water is about 39 degrees Farenheit (4 degrees Celsius), which is just above freezing!








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