99 Fun Facts About Oceans

Which is the smallest and shallowest of Earth's five oceans?

The Arctic Ocean is the smallest and shallowest of the five oceans; it is nearly landlocked by Eurasia and North America and covered by sea ice for much of the year.

Which ocean contains the Mariana Trench, the deepest known point on Earth?

The Mariana Trench, home to the Challenger Deep, is located in the western Pacific Ocean and is the deepest oceanic trench on Earth.

By what process do ocean plants and phytoplankton turn sunlight into energy?

Photosynthesis in phytoplankton and marine plants converts sunlight, carbon dioxide and water into energy and oxygen, forming the base of most marine food webs.

Approximately what percentage of Earth's surface is covered by oceans?

Oceans cover about 71% of the Earth's surface and contain more than 97% of the Earth's water.

Which marine mammal makes the longest migration of any mammal?

The gray whale's round trip from Arctic feeding grounds to breeding lagoons in Mexico runs 10,000 to 12,000 miles, the longest migration of any mammal.

The Ring of Fire, a horseshoe-shaped belt of volcanoes and earthquakes, runs around the rim of which ocean?

The Pacific Ocean basin is ringed by subduction zones, which give the horseshoe-shaped Ring of Fire its frequent earthquakes and volcanic eruptions.

What is it called when cold, nutrient-rich deep water rises to the ocean surface, creating rich fishing grounds?

Upwelling brings nutrients up from the deep to feed the food chain, which is why upwelling zones make some of the best fishing grounds.

Which marine ecosystem is nicknamed the 'rainforests of the sea' for its biodiversity?

Shallow coral reefs, built by tiny polyps, form some of Earth's most diverse ecosystems, hence the rainforest nickname.

Who reached the Challenger Deep with Jacques Piccard in 1960?

Don Walsh, then a US Navy lieutenant, and Swiss oceanographer Jacques Piccard were the first two people to reach the Challenger Deep, in the bathyscaphe Trieste in 1960.

Which hypersaline 'sea' is a landlocked lake between Jordan and Israel and the West Bank?

The Dead Sea, a landlocked lake bordered by Jordan, Israel and the West Bank, is about 304 metres deep and roughly ten times saltier than the ocean, so swimmers float effortlessly.

Which effect deflects ocean currents to the right in the Northern Hemisphere?

The Coriolis effect, a product of Earth's rotation, deflects moving water to the right in the Northern Hemisphere and to the left in the Southern, shaping the great circular gyres.

Which undersea mountain range surfaces at Iceland, where two tectonic plates pull apart?

The Mid-Atlantic Ridge, where the North American and Eurasian plates spread apart, rises above sea level in Iceland and runs roughly 16,000 km along the Atlantic floor.

What share of Earth's water surface does the Pacific cover?

The Pacific covers about 46% of Earth's water surface; its 165 million square kilometres make it the largest division of the World Ocean.

Which explorer coined the name 'Pacific' in 1520 after meeting favourable winds?

Ferdinand Magellan named it Mar Pacífico in November 1520 after finding calm seas beyond the strait; Balboa had sighted it from Panama in 1513 and called it the South Sea.

The Horizon Deep, the deepest point in the Southern Hemisphere, lies in which deep-sea feature?

The Horizon Deep in the Tonga Trench reaches about 10,820 metres, second only to the Challenger Deep in the Mariana Trench.

The Atlantic is named after which figure of Greek mythology?

Herodotus called it Atlantis thalassa, the Sea of Atlas, around 450 BC.

The Atlantic's deepest point, the Milwaukee Deep, lies where?

The Milwaukee Deep lies in the Puerto Rico Trench; at about 8,376 metres it is more than two kilometres shallower than the Challenger Deep.

Which is the warmest of the world's oceans?

The Indian Ocean is the warmest of the oceans; it covers about 20% of the planet's water area and its heat drives the Asian monsoons.

Ancient Greek geographers knew the ocean south of Asia by what name?

Greek writers called it the Erythraean Sea, as in the first-century Periplus of the Erythraean Sea, a sailing guide to its ports and trade routes.

Some oceanographers refuse to call Earth's smallest ocean an ocean, preferring which name?

Because it is almost enclosed by land, some oceanographers class it as the Arctic Mediterranean Sea; the IHO lists it as an ocean of about 14 million square kilometres.

In which year did the International Hydrographic Organization define the Southern Ocean as south of 60°S?

In 2000 the IHO's draft fourth edition of Limits of Oceans and Seas defined the Southern Ocean as the waters south of 60°S; a naming dispute elsewhere in the publication stalled its formal adoption.

Which explorer's 1770s voyages proved that water encircled the globe's southern latitudes?

James Cook's second voyage of 1772–75 crossed the Antarctic Circle and circled the globe at high southern latitudes, showing open water ringed the south rather than a great southern continent.

How long is the crescent-shaped Mariana Trench?

The Mariana Trench is about 2,550 km long but only about 69 km wide, and its floor sits more than 2 km deeper than Everest is tall.

Water pressure at the bottom of the Mariana Trench is roughly how many times that at sea level?

Pressure at the Challenger Deep is about 1,086 bar, roughly 1,072 times sea-level pressure, or about eight tons per square inch.

The Challenger Deep lies inside the exclusive economic zone of which country?

The Challenger Deep sits inside the exclusive economic zone of the Federated States of Micronesia, which is why the 2009 US Marianas Trench Marine National Monument does not include it.

The Great Barrier Reef is composed of over how many individual reefs?

The Great Barrier Reef comprises over 2,900 individual reefs and some 900 islands, stretching more than 2,300 km along Queensland's coast.

A 2012 study found the Great Barrier Reef had lost roughly how much of its coral cover since 1985?

The October 2012 PNAS study by De'ath and colleagues found the reef had lost 50.7% of its coral cover since 1985, more than half, blamed on storms, crown-of-thorns starfish and bleaching.

The Sargasso Sea is unusual among seas because it is bounded by what rather than land?

The Gulf Stream, North Atlantic, Canary and North Atlantic Equatorial currents form its clockwise gyre.

Johannes Schmidt's 1920–22 Dana expeditions found that which animal breeds in the Sargasso Sea?

Danish biologist Johannes Schmidt traced ever-smaller eel larvae across the Atlantic and concluded that the European eel spawns in the Sargasso Sea, publishing his findings in 1923.

Which American polymath had a chart of the Gulf Stream printed in London in 1769?

Benjamin Franklin drew on his cousin Timothy Folger, a Nantucket whaling captain, for the Franklin–Folger Gulf Stream chart, first printed in London in 1769; British packet captains largely ignored it.

Which explorer's 1513 expedition gave Europeans their first record of the Gulf Stream?

Juan Ponce de León's April 1513 log off Florida records a current so strong that his ships were pushed backwards despite a fair wind.

Which climate scientist coined the term 'global conveyor belt' for the thermohaline circulation?

Wallace Smith Broecker of Columbia's Lamont-Doherty Earth Observatory coined the 'global conveyor belt' image; its two limbs are the Atlantic meridional overturning circulation and the Southern Ocean overturning circulation.

What is the average salinity of seawater?

That is 35 grams of dissolved salt per litre, mostly sodium and chloride.

Which is the most saline open sea in the world?

The Red Sea's salinity reaches about 40 parts per thousand because high evaporation, scant rainfall, no permanent rivers and a narrow outlet at Bab-el-Mandeb pile up the salt.

At typical salinity, seawater freezes at about what temperature?

Seawater at 35 parts per thousand salinity freezes at about −2 °C (−1.9 °C), because dissolved salt lowers the freezing point below that of fresh water.

Which enzyme catalyses the light-producing reaction behind most bioluminescence?

Luciferase catalyses the oxidation of luciferin, releasing light; Robert Boyle showed in 1667 that the glow of rotting wood needs air.

The 'deep sea' is broadly defined as beginning at what depth, where light begins to fade?

The deep sea is usually taken to begin at about 200 metres, the base of the sunlit epipelagic zone; below lie the bathyal, abyssal and hadal zones, the last reaching 11 km.

What is the falling organic debris that feeds many deep-sea creatures called?

It is made of algal particles, detritus and other biological waste sinking from the sunlit layers.

What temperature did vent fluid reach at 5°S on the Mid-Atlantic Ridge in 2008?

Vent fluid at 5°S on the Mid-Atlantic Ridge was measured at 464 °C in 2008; at that depth and pressure the fluid is supercritical, neither gas nor liquid.

The Beebe vent field, a hydrothermal site about 5,000 m deep found in 2010, lies where?

The Beebe vent field lies on the Mid-Cayman Rise in the Cayman Trough; its black smokers vent fluid at about 401 °C nearly 5,000 m below the surface.

Point Nemo, the oceanic pole of inaccessibility, is roughly how far from the nearest land?

Point Nemo in the South Pacific lies about 2,688 km from the nearest land (Ducie Island, Motu Nui and Maher Island); astronauts on the ISS overhead are sometimes the closest humans.

The Japanese word tsunami literally means what?

Tsunami combines the Japanese tsu (harbour) and nami (wave), 'harbour wave'; Thucydides in 426 BC was the first to link such waves to undersea earthquakes.

The bathyscaphe Trieste, first crewed vessel to reach the Challenger Deep, used tanks of what for buoyancy?

Trieste's float held about 85,000 litres of gasoline, lighter than water and nearly incompressible, for buoyancy; designed by Auguste Piccard, it was bought by the US Navy in 1958.

Between 1950 and 2020, the average pH of the ocean surface fell from about 8.15 to what?

Surface pH fell from about 8.15 in 1950 to 8.05 by 2020; that 0.1 drop means about 26% more hydrogen ions, bad news for shell-building organisms.

Which yachtsman publicised the Great Pacific Garbage Patch after sailing through it in 1997?

Charles Moore, a racing yachtsman, crossed the North Pacific Gyre in 1997 on his way home from the Transpac race and found plastic debris everywhere, bringing the Great Pacific Garbage Patch to public attention.

What is the average depth of the world's oceans?

The oceans average about 3,700 metres deep; nearly half of all marine waters lie below 3,000 metres, and the deep ocean below 200 metres covers about 66% of the planet's surface.

By 2024, what share of the ocean floor had been mapped at better-than-satellite resolution?

Seabed 2030 reported in June 2024 that just over 26% of the seafloor had been directly mapped by ship-borne sonar; the rest is known only from coarse satellite altimetry.

What is the deepest pelagic zone, covering the ocean trenches from 6,000 to 11,000 metres, called?

The hadalpelagic zone, named for Hades, fills the trenches from about 6,000 to 11,000 metres; the abyssopelagic above it bottoms out at around 6,000 metres on the abyssal plain.

What is the combined volume of water in all the oceans?

The oceans hold about 1.3 billion cubic kilometres of water (1.335 billion km³, or 1.335 sextillion litres), about 97% of all water on Earth.

Pillow basalt from which Greenland rock formation shows water existed on Earth 3.8 billion years ago?

Pillow basalts in the Isua supracrustal belt of southwest Greenland, about 3.8 billion years old, formed when lava erupted underwater; Quebec's Nuvvuagittuq rocks may push the evidence back further.

Which is the second largest of the world's five oceans?

The Atlantic covers about 85 million square kilometres, roughly half the area of the Pacific.

The Bay of Fundy's tidal range, among the largest on Earth, reaches roughly how many metres?

Tidal resonance in the funnel-shaped bay amplifies tides to about 16 metres, against a worldwide average of roughly one metre.

The 1995 Draupner wave, the first rogue wave measured by instrument, hit a platform in which sea?

A laser on the Draupner gas platform off Norway caught the wave on New Year's Day 1995, proving rogue waves were real.

The 1872–76 voyage that laid the foundations of oceanography was made aboard which Royal Navy ship?

HMS Challenger, a converted corvette, was refitted at Sheerness with natural history and chemistry laboratories before sailing from Portsmouth in December 1872 on a voyage of nearly 69,000 nautical miles.

Which film director made a solo dive to the Mariana Trench's deepest point on 26 March 2012?

James Cameron's Deepsea Challenger was only the second crewed craft to reach the Challenger Deep, 52 years after Trieste in 1960.

Victor Vescovo's 2018–19 dives to the bottom of all five oceans used which submersible?

DSV Limiting Factor, a two-person Triton 36000/2 with a titanium pressure sphere, made the Five Deeps dives from the support ship DSSV Pressure Drop.

William Beebe and Otis Barton reached a record 923 m off Bermuda in 1934 in which vessel?

The Bathysphere, an unpowered steel ball lowered on a cable, took Beebe and Barton to 923 m on 15 August 1934; Barton broke the record in 1949 in the Benthoscope.

Which submersible, commissioned in 1964, carried Robert Ballard to the Titanic wreck in 1986?

Alvin, named for oceanographer Allyn Vine and operated by Woods Hole, also helped find a lost hydrogen bomb off Palomares, Spain, in 1966.

In which year did scientists first find hydrothermal vents teeming with life?

In 1977 researchers aboard Alvin found vents on the Galápagos Rift crowded with tube worms and clams; until then deep life was thought to depend on sunlight, but vent communities run on chemosynthesis.

What is the largest living species of fish?

The whale shark, a slow filter-feeder that can exceed 12 metres, is the largest living fish; the basking shark is a distant second.

What is the largest animal known to have ever existed?

The blue whale outweighs any dinosaur, reaching up to 30 metres and around 200 tonnes.

Researchers from which country took the first photos of a live giant squid in its habitat, in 2004?

Tsunemi Kubodera and Kyoichi Mori shot the images off the Ogasawara Islands and released them a year later.

Which 'living fossil' fish turned up in a fisherman's catch off South Africa in December 1938?

The coelacanth, thought extinct for 66 million years, was spotted by museum curator Marjorie Courtenay-Latimer in an East London trawler's catch; the genus Latimeria carries her name.

The Argo programme tracks ocean temperature and salinity with a global fleet of thousands of what?

Argo's profiling floats drift at depth, sink to 2,000 metres, rise to the surface about every ten days and report by satellite, giving a near-real-time picture of the upper ocean.

Which oceanographer is nicknamed 'Her Deepness'?

Sylvia Earle has also been dubbed 'The Sturgeon General', and her 1979 JIM-suit dive to the seafloor off Oahu was untethered.

What was the name of Jacques Cousteau's famous research ship?

Calypso, a former Royal Navy minesweeper, was bought by Thomas Loel Guinness in 1950 and leased to Cousteau for a symbolic one franc a year.

World Oceans Day is celebrated each year on which date?

World Oceans Day falls on June 8, proposed at the 1992 Rio Earth Summit and recognised by the UN in 2008; Earth Day is April 22 and World Water Day March 22.

The Drake Passage separates Antarctica's South Shetland Islands from which headland of Chile?

The Drake Passage runs between Cape Horn and the South Shetland Islands; Spanish speakers call it the Mar de Hoces after Francisco de Hoces, who may have sighted it in 1525.

Which Dutch navigator was first to sail through the Drake Passage, in 1616?

Francis Drake gave the passage its English name but did not sail through it; Schouten did, 38 years later.

Roughly how wide is the Bering Strait at its narrowest point?

The Bering Strait is about 82 km wide at its narrowest, between Cape Dezhnev in Russia and Cape Prince of Wales in Alaska, the continents' closest mainland points.

At its narrowest, roughly how far apart are Europe and Africa across the Strait of Gibraltar?

The Strait of Gibraltar narrows to about 14 km (7.7 nautical miles) between Point Marroquí in Spain and Point Cires in Morocco, close enough that swimmers cross between the continents.

What is the largest sea in the world by surface area?

The Philippine Sea spans about 5 million square kilometres of the western Pacific east of the Philippine archipelago, ahead of the Coral and Arabian seas.

In the Messinian salinity crisis about 5.96 million years ago, which sea nearly dried up?

The precursor of the Strait of Gibraltar closed, and the basin dried out almost completely within about a thousand years.

Ancient shipwrecks survive intact in which sea thanks to a permanent, oxygen-free deep layer?

Below about 150 metres the Black Sea is permanently anoxic, so wood-boring organisms cannot live there; a survey in 2018 found a Greek wreck about 2,400 years old intact.

Which sea is the world's largest basin of brackish water?

The Baltic Sea, fed by many rivers and linked to the North Sea only through narrow Danish straits, has surface salinity under 1%, making it the world's largest brackish basin.

Which supercontinent was ringed by a single superocean about 250 million years ago?

Pangaea, assembled about 300 million years ago, was surrounded by the superocean Panthalassa, Greek for 'all sea'; the modern Pacific is its shrunken remnant.

The world's widest continental shelf, stretching 1,500 km, lies off which coast?

The Siberian Shelf under the Barents, Kara, Laptev and East Siberian seas extends up to 1,500 km from shore, the widest continental shelf on Earth.

Peruvian fishermen named the El Niño climate pattern after whom?

The warm current peaked around Christmas, so fishermen called it El Niño de Navidad, the Christ Child; its cold counterpart was later named La Niña.

The Great Blue Hole, a giant marine sinkhole, lies off the coast of which country?

The Great Blue Hole lies in Lighthouse Reef about 70 km off the coast of Belize; it is roughly 300 metres across and 125 metres deep, and Cousteau ranked it among his top dive sites.

A tiny male deep-sea anglerfish fusing permanently to a female is an example of what?

Sexual parasitism: the fused male's tissues and blood vessels join the female's and he becomes little more than a sperm supply, a natural case of parabiosis.

Which cephalopod curls its webbed arms back over its body when threatened?

The vampire squid, Vampyroteuthis infernalis, responds to threats by curling its webbed arms back over its mantle into a spiny 'pineapple posture' rather than fleeing or inking.

Vincent Gaddis coined 'The Deadly Bermuda Triangle' in a 1964 article for which magazine?

Gaddis's article ran in the February 1964 issue of the pulp magazine Argosy; he expanded it into the book Invisible Horizons in 1965.

Greenland sharks, the longest-lived vertebrates, have a lifespan of at least how many years?

A 2016 radiocarbon study of eye lenses put one Greenland shark at 392 years, give or take 120, so at least 272 years, possibly older than the United States.

Which seabird makes the longest migration in the animal kingdom?

An Arctic tern tagged on England's Farne Islands in 2015 covered 96,000 km in ten months, flying from the North Sea to Antarctica and back.

The Molloy Deep, about 5,550 m down, is the deepest point of which ocean?

The Molloy Deep in the Fram Strait is the Arctic Ocean's deepest point; the Five Deeps Expedition measured it at 5,550 m in 2019, the shallowest of the five ocean bottoms.

What share of Zealandia, the submerged continent, lies underwater?

About 94% of Zealandia's 4.9 million square kilometres lies underwater; it broke from Gondwana 83–79 million years ago and subsided, leaving New Zealand and New Caledonia as its high points.

Scientists have judged which Antarctic sea to have the clearest water of any sea?

In the Weddell Sea in October 1986 a Secchi disc remained visible at 80 metres, a clarity matching distilled water.

Soviet expeditions in 1948 discovered which undersea feature running near the North Pole?

It is named after the 18th-century polymath Mikhail Lomonosov and is central to rival polar seabed claims.

The Java Trench holds the deepest point of which ocean?

The Java (Sunda) Trench holds the Indian Ocean's deepest point; Victor Vescovo measured 7,192 m there in 2019, about 500 km south of Bali.

Cold seeps were first discovered in 1983 on the Florida Escarpment in which body of water?

Alvin's crew found tubeworms and mussels living on brine seeping from the base of the Florida Escarpment in the Gulf of Mexico, about 3,200 m down, in 1983.

Which flow, moving about 137 million cubic metres of water a second, is the ocean's largest?

The Antarctic Circumpolar Current circles Antarctica unbroken by land, so it can grow to about 137 million cubic metres a second, more than 100 times the flow of all rivers combined.

The Kuroshio, the warm current flowing past Japan, has a name meaning what?

Kuroshio means 'Black Stream' or 'Black Tide' in Japanese, a reference to the deep blue of its water; it is also called the Japan Current.

The cold Humboldt Current off South America is also named after which country?

The Humboldt Current is also called the Peru Current; its nutrient-rich upwelling supports one of the world's richest anchovy fisheries off Peru.

A sunken whale carcass can sustain a deep-sea ecosystem for roughly how long?

A whale fall can feed a deep-sea community for decades, passing through scavenger, enrichment and sulphur-loving stages, each with its own animals.

Which Russian microbiologist proposed chemosynthesis in 1890, long before vents were found?

Sergei Winogradsky showed in 1887–90 that Beggiatoa bacteria gain energy by oxidising hydrogen sulphide, the basis of chemosynthesis, confirmed in the deep sea when vent life was found in 1977.

The 10,047 m Kermadec Trench lies north-east of which country?

The Kermadec Trench runs about 1,000 km north-east of New Zealand, from the Hikurangi Plateau to the Louisville Seamount Chain, reaching 10,047 m.

Which French physicist worked on active sound devices to detect submarines in 1915?

Paul Langevin, working with Russian émigré engineer Constantin Chilowsky from 1915, built piezoelectric quartz transducers that laid the groundwork for sonar.

Which author's 1896 book 'The Seven Seas' tied that phrase to the world's oceans?

Rudyard Kipling's 1896 verse collection The Seven Seas fixed the phrase in modern English; medieval Arabs, Greeks and Romans each had their own different lists of seven seas.

How many major subtropical gyres circulate in the world's oceans?

There are five major subtropical gyres: North and South Atlantic, North and South Pacific, and the Indian Ocean gyre; each collects drifting plastic.