The ocean covers 70 percent of itEarth's surface. It contains about 1.35 billion cubic kilometers (324 million cubic miles) of water, or about 97 percent of all water on Earth. The ocean supports all life on earth and makes the planet appear blue when viewed from space. Earth is the only planet in ourssolar systemthat's definitely known to containfluidWater.
Although the ocean is a continuous body of water,Oceanographenhave divided it into five main areas: Pacific, Atlantic, Indian, Arctic and Southern Oceans. The Atlantic, Indian and Pacific Oceans merge into icy waters around Antarctica.
The ocean plays an important role in climate andWetter. The sun's heat causes waterevaporate, adding moisture to the air. The oceans provide most of this evaporated water. The watersteam condensedform clouds that give off their moisture as rain or other types of moistureprecipitation. All life on earth depends on this process, known aswater cycle.
Diethe atmospheregets much of its heat from the ocean. As the sun warms the water, the ocean transfers heat to the atmosphere. The atmosphere againdistributedthe heat around the world.
Because waterabsorbedand loses heat more slowly than land masses, the ocean contributes to the global balancetemperaturesby absorbing heat in summer and releasing it again in winter. Without the sea to helpregulateglobal temperatures, the earth's climate would be bitterly cold.
After the earth began to form about 4.6 billion years ago, it gradually separated into layers of lighter and heavier rock. The lighter rock rose and formed the earthcrust. The heavier rock sank and formed the earthAderandMantel.
The waters of the ocean came out of rocks within the newly forming earth. As themeltedRocks cooled, releasing water vapor and other gases. Eventually the water vapor condensed and covered the crust with aPrimitiveOcean. Even today, hot gases from the earth's interior produce new water at the bottom of the sea.
Scientists began mapping the ocean floor in the 1920s. They used instruments calledEcholote, who measure water depths withsound waves. Use sonarSonarTechnology. Sonar is an acronym for SOund Navigation And Ranging. The sonar showed the seabed has dramatic physical features, including huge mountains, deepcanyons, steepcliffs, and widelevels.
The ocean's crust is a thin layer of volcanic rockBasalt. The seabed is divided into different areas. The first is theContinental plate, the near-flat underwater extension of a continent. Continental shelves vary in width. They are usually wide along low-lying land and narrow along mountainous coasts.
A shelf is coveredSedimentfrom the nearby continent. Some of the sediment is deposited by rivers and contained by features such as natural levees. Most of the sediment comes from the lastice age, or ice age when the oceansdeclinedand exposed the continental shelf. This sediment is calledRelict Sediment.
At the outer edge of the continental shelf, the land drops steeply into the so-called shelfContinental slope. The slope drops almost to the bottom of the ocean. It then tapers into a gentler slope known as the Continental Rise. The continental rise descends to the deep-sea floor referred to as thedeep sea plain.
Abyssal plains are vast, flat areas that lie at depths of about 4,000 to 6,000 meters (13,123 to 19,680 ft). Deep sea plains cover 30 percent of the ocean floor and are the shallowest feature on Earth. They are covered by fine-grained sediments such as clay and silt.pelagicSediments, the remains of small marine organisms, also drift down from the upper layers of the ocean. Scattered across the Abyssal Plains are abyssal mounds and underwater volcanic pinnacles called seamounts.
From the abyssal plains in every great ocean rises a vast chain of mostly submarine mountains. called themid-ocean ridge, the chain orbits the earth and stretches more than 64,000 kilometers (40,000 miles). Much of the mid-ocean ridge is split by a deep central rift or fissure. Mid-ocean ridges mark the boundaries between themtectonic plates. Molten rock from the Earth's interior swells out of the crack and forms in a process known asspreading of the seafloor. A main compartmentPortionof the ridge runs down the middle of the Atlantic Ocean and is known as the Mid-Atlantic Ridge. It was not directly seen or explored until 1973.
Some areas of the sea floor have deep, narrow depressions called the oceanditches. They are the deepest parts of the ocean. The lowest point of all is thischallenger deep, which lies in theMarianengrabenin the Pacific Ocean near the island of Guam. Its true depth is unknown, but the most accurate measurements show that the Challenger Deep lies 11,000 meters (36,198 feet) below the sea surface — that's more than 2,000 meters (6,000 feet) higher than Mount Everest, the highest point on earth. thePrintat the Challenger Deep is about eight tons per square inch.
marine life zones
From the coast to the deepest seabed, the oceanteemingwith life. The hundreds of thousands ofMarineTypes range frommicroscopic algaeto the largest creature that has ever walked the earth, the blue whale.
The ocean has five major life zones, each with organismsuniquecustomized to their specific navyecosystem.
Dieepipelagische Zone(1) is the sunlit upper layer of the ocean. It extends from the surface to a depth of about 200 meters. Also known as the photic or euphotic zone, the epipelagic zone can exist in both lakes and the ocean.
The sunlight in the epipelagic zone allows itphotosynthesishappen. Photosynthesis is the process by which some organisms convert sunlight andcarbon dioxidein Energy uoxygen. In the ocean, photosynthesis takes place in plants and algae. Plants like seagrass are similar to land plants—they have roots, stems, and leaves. Algae are a type of aquatic organisms that can photosynthesize sunlight. Large algae such as seaweed are mentionedSeetang.
Phytoplanktonalso live in the epipelagic zone. Phytoplankton are microscopic organisms that include plants, algae and bacteria. They only become visible when billions of them formAlgenblüte, and appear as green or blue spots in the ocean.
Phytoplankton is a foundation of the oceanfood web. Through photosynthesis, phytoplankton are responsible for nearly half of the oxygen released into the Earth's atmosphere. animals such askrill(a type of shrimp), fish and microscopic organismsZooplanktonAll eat phytoplankton. These animals, in turn, are eaten by whales, larger fish, seabirds, and humans.
The next zone down, which extends to a depth of approximately 1,000 meters, is themesopelagische Zone(2). This zone is also calledtwilight zonebecause the light is very weak there. Due to the lack of sunlight, there are no plants in the mesopelagic zone, but large fish and whales dive there to huntprey. Fish in this zone are small andbright. One of the most common is the lanternfish, which has organs on its side that produce light.
Sometimes animals from the mesopelagic zone (such as sperm whales (Physeter macrocephalus) and squid) dive into thebathypelagic Zone(3), which is about 4,000 meters (13,100 feet) deep. The bathypelagic zone is also referred to as themidnight zonebecause no light reaches him.
Animals that live in the bathypelagic zone are small, but they often have huge mouths, sharp teeth, andexpandableStomach's that let them eat all the food that comes by. Most of this food comes from the remains of plants and animals brought down from the upper pelagic zones. Many bathypelagic animals do not have eyes because they are not needed in the dark. Because the pressure is so great and it's so hard to findnutrientFish in the bathypelagic zone move slowly and have strong gills to extract oxygen from the water.
The water at the bottom of the ocean, theabessopelagische Zone(4), is very salty and cold (2 degrees Celsius or 35 degrees Fahrenheit). At depths down to 6,000 meters (19,700 feet), the pressure is very strong - 11,000 pounds per square inch. This makes it impossible for most animals to live. Animals in this zone are bizarreadjustmentscope with their ecosystem. Many fish have jaws that look out of joint. The jaws allow them to drag their open mouth across the sea floor to find food such as clams, shrimp, and microscopic organisms.
Many of the animals in this zone, including squid and fish, are bioluminescent. Bioluminescent organisms generate light through chemical reactions in their bodies. One species of anglerfish, for example, has a luminous growth stretching out in front of its huge, toothy maw. When smaller fish are attracted to the light, the anglerfish simply snaps its jaws to eat its prey.
The deepest sea zone found in ditches and canyons is referred to as TheHadalpelagische Zone(5). Few organisms live here. This includes tinyisopods, Kind ofcrustaceanrelated to crabs and shrimp.
invertebratessuch as sponges and sea cucumbers thrive in the Abessopelagic and Hadalpelagic zones. Like many starfish and jellyfish, these animals rely almost entirely on falling dead or dead partsexpiredcalled plants and animalssea debris.
However, not all bottom dwellers depend on marine debris. In 1977, oceanographers discovered a community of creatures on the sea floor feeding on bacteria around what are known as ventshydrothermalair vents. These vents drain superheated waterenrichedwithmineralsfrom the interior of the earth. The minerals feed unique bacteria, which in turn feed critters like crabs, clams, and tubeworms.
Currents are streams of water flowing through a larger body of water. Oceans, rivers and streams have currents. the oceanssalinityand temperature as well as the geographical conditions of the coast determine the behavior of an ocean current. Earthrotationand wind also affect ocean currents. Currents flowing near the surface transport heat from the surfacetropicsto theThe rodand moving back toward cooler waterequator. This keeps the ocean from getting extremely hot or cold.
Deep, cold currents carry oxygen to organisms throughout the ocean. They also carry rich stores of nutrients that all living things need. The nutrients come from plankton and the remains of other organisms that drift down and decay on the sea floor.
Along some coasts, winds and currents create a phenomenon calledboost. When the wind pushes the surface water away from the shore, deep streams of cold water rise to take its place. This buoyancy of deep water brings nutrients to the top, which feed new plankton and provide food for fish. oceanfood chainconstantrecyclefood and energy in this way.
Some ocean currents areenormousand extremely powerful. One of the strongest is thatgulf stream, a warm surface current that originates in the tropical Caribbean Sea and flows northeast along the east coast of the United States. The Gulf Stream is up to 80 kilometers wide and more than a kilometer deep.
Like other ocean currents, the Gulf Stream plays a major role in climate. As the current travels north, it transfers moisture from its warm tropical waters into the air above. Westerly or prevailing winds carry the warm, humid air to the British Isles and toScandinavia, resulting in them having milder winters than they would otherwise experience in their northlatitudes. The northern parts of Norway are close to the Arctic Circle but remain ice-free for most of the year due to the Gulf Stream.
The weather pattern known as El Niño involves a change in the Humboldt Current (also known as the Peru Current) off the west coast of South America. InThe childconditions, a current of warm surface water flows eastward along the equator, preventing the normal upwelling of the cold, nutrient-rich Humboldt Current. El Niño, which can devastate the fisheries of Peru and Ecuador, occurs every two to seven years, usually in December.
The paths of ocean currents are determined in part by the Earth's rotation. This is known as theCoriolis force. It causes large systems such as winds and ocean currents that would normally move in a straight line to drift to the rightnorthern hemisphereand left insouthern hemisphere.
people and the sea
For thousands of years, humans have depended on the ocean for both food and waterRouteProactandexploration. Even today, people still travel the seas and rely on the resources it contains.
Nations continue to negotiate how to determine the extent of their violenceAreabeyond the shore. United Nations Law of the Seacontractestablished Exclusive Economic Zones (EEZs) expanding 200nautical miles(230 miles) beyond the shore of a nation. Although some countries have not signed or ratified the treaty (including the US), it is considered the standard.
Russia has proposed extending its EEZ beyond 200 nautical miles because two mid-ocean ridges, the Lomonosov and Medeleev Ridges, are extensions of Russia's continental shelf. This area includes the North Pole. Russian explorers in asubmersibleIn 2007, a vehicle hoisted a metal Russian flag in the disputed area.
Over the centuries, people have sailed across the oceantrade routes. Today, ships still carry most of the worldfreight, particularly bulky goods such as machines, grain, etcoil.
Ocean ports are areas ofHandeland culture. Water and land transport meet there and people from different professions: business people whoimportandExportGoods and services; Dockers loading and unloadingcharge; and ship crews. Ports also have high concentrations of migrants and immigrants with a variety of ethnicities, nationalities, languages and religions.
Important ports in the USA are New York/New Jersey and New Orleans. The busiest ports in the world include the port of Shanghai in China and the port of Rotterdam in the Netherlands. Seaports are also important to a nation's armed forces. Some ports are used exclusively forMilitary-purposes, although most share space withcommercialCompany. "The sun never sets on the British Empire" is a phrase used to explain the extent of the EmpireGreat Britain, mostly in the 19th century. Although based on the small European island nation of Great Britain, British military naval power expanded its empire from Africa to America, Asia and Australia.
Scientists and other experts hope that the ocean will be used as a source on a larger scalerenewable energy. Some countries have already done soclampedthe energy of ocean waves, temperatures, currents, or tides to drive turbines and generate electricity.
One source of renewable energy is generators powered by electricitytidal streamsor ocean currents. They convert the movement of currents into energy. Sea current generators have not been developed on a large scale but are working in some places in Ireland and Norway. Someconservationistcriticize the effects of large-scale construction on the marine environment.
Another source of renewable energy isConversion of sea thermal energy(OTEC). It uses the temperature difference between warm surface water and cold deep water to power a motor. OTEC plants are located in places with significant differences in sea depth: for example in Japan, India and the US state of Hawaii.
An emerging source of renewable energy issalt gradient performance, also known as osmotic power. It is a source of energy that harnesses the power of fresh water merging into salt water. This technology is still under development but has potential inDeltaAreas where fresh river water constantly interacts with the ocean.
Fishermen catch more than 90 million tons of seafood every year, including more than 100 species of fish andshellfish. Millions of people, from commercial fishermen to business owners such as restaurant owners and boat builders, depend on fishinglivelihood. Fishing can be classified in two ways. In subsistence fishing, fishermen use their catch to meet the nutritional needs of their families or communities. Incommercial fishingFishermen sell their catch for money, goods or services. Popular subsistence and commercial fish include tuna, cod and shrimp.
Deep sea fishing is also a popular recreational sport.sport fishingcan be competitive or non-competitive. In sport fishing tournaments, individuals or teams compete for prizes based on the size of a specific species caught over a specific period of time. Both competitive and non-competitive sport fishermen require licenses to fish and may or may not keep the fish they catch. Sport fishermen are increasingly practicingcatch and releaseFishing, in which a fish is caught, measured, weighed and often captured on film before being released back into the sea. Popularwild fish(fish caught for sport) are tuna and marlin.
whalingis a style of fishing that theharvestof whales and dolphins. It has declined in popularity since the 19th century but is still a way of life for many cultures such as Scandinavia, Japan, Canada and the Caribbean.
The ocean offers an abundance of fishing and whaling resources, but these resources are under threat. Humans have harvested so much fish and marine life for food and other products that some species have disappeared.
In the 1800s and early 1900s, whalers killed thousands of whales for whale oil (wax made from boiled walnut oil).Speck) andivory(whale teeth). Some species, including the blue whale (Balaenoptera Musculus) and the right whale, were almost too hunteddie out. Many species are still extantendangeredtoday.
In the 1960s and 1970s, catches of important food fish such as herring in the North Sea and anchovies in the Pacific began to plummet. Governments took note of thisoverfishing– Harvesting more fish than the ecosystem can handlefill up. Fishermen were forced to go further out to sea to find fish, putting them at risk. (Deep-sea fishing is one of the most dangerous professions in the world.) Now they use advanced gadgets like electronic fish finders and largegillnetsortrawlingNets to catch more fish. This means there are far fewer fish to breed and replenish the stock.
In 1992, the collapse or disappearance of cod in the Grand Banks of Newfoundland, Canada put 40,000 fishermen out of work. Cod fishing was banned, and to this day, neither the cod nor the fishery has recovered.
To catch the dwindling fish stocks, most fishermen use trawl nets. They pull the nets across the seabed and across acres of ocean. These nets accidentally catch many small, juvenile fish and mammals. Animals caught in fishing nets intended for other species are namedBeifang. The fishing industry and fisheries authorities are at odds over how to tackle the problem of bycatch and overfishing. Those involved in the fishing industry do not want to lose their jobs, while conservationists want to maintain healthy fish stocks in the sea.
A number ofconsumerdecide to buysustainable seafood. Sustainable seafood is harvested from sources (either wild or farmed) that do not deplete the natural ecosystem.
mining and drilling
Many minerals come from the sea.sea-saltis a mineral that has been used as a flavoring and preservative since ancient times. Sea salt contains many additional minerals, such as B. Calcium, which ordinary table salt lacks.
Hydrothermal vents often formMassive sulphide deposits (SMS) on the sea floorthat contain precious metals. These SMS deposits are found on the seafloor, sometimes in the deep sea and sometimes closer to the surface. New techniques are being developed to mine the seabed for valuable minerals such as copper, lead, nickel, gold and silver. Mining companies employ thousands of people and provide goods and services for millions more.
Critics of underwater mining claim it disturbs the localecology. Organisms—corals, shrimp, clams—that live on the ocean floor have theirshabitatdisturbed, disrupting the food chain. In addition, habitat destruction threatens the viability of species that have a narrow habitatniche. Maui-Delfin (Cephalorhynchus hectori maui) for example is an endangered species native to the waters of the North Island of New Zealand. The number of Maui dolphins is already reduced due to bycatch. Seabed mining threatens its habitat and puts it at further risk of extinction.
Oil is one of the most valuable resources extracted from the sea today.Off-Shore oil rigsPumpPetroleumfrom wells drilled into the continental shelf. About a quarter of all oil and natural gas supplies today come from offshore oil fields around the world.
Offshore drilling is expensiveengineering. An oil platform can be erected directly on the seabed or it can “float” over an anchor. Depending on how far out on the continental shelf an oil rig is located, workers may need to be flown in. Subsea or underwater installations are complicated groups of interconnected drilling rigs and a single drilling rig. Underwater production often requires remotely operated underwater vehicles (ROVs).
Some countries are investing in offshore drilling for profit and to avoid dependence on oil from other regions. The Gulf of Mexico near the US states of Texas and Louisiana is heavily drilled. Several European countries, including the UK, Denmark and the Netherlands, drill in the North Sea. However, offshore drilling is a complicated and expensive program. There are a limited number of companies that have the knowledge and resources to work with local governments to construct offshore oil platforms. Most of these companies are based in Europe and North America, although they operate worldwide.
Some governments have banned offshore oil drilling. They cite safety and environmental concerns. There have been several accidents where the platform itself exploded, costing many lives. Offshore drilling also poses a threat to the ocean ecosystem. Spills and leaks from oil rigs and oil tankers that transport the material seriously harm marine mammals and birds. Oil coats feathers and affects the birds' ability to maintain and maintain their body temperaturelivelyin the water. The fur of otters and seals also becomes coated and oil penetratesdigestive tractfrom animals can damage their organs.
Offshore rigs also release metal shavings, tiny amounts of oil, and moredrilling fluidinto the sea every day. Drilling fluid is the fluid used with machines to drill holes deep into the planet. This liquid may containpollutantssuch aspoisonouschemicalsheavy metals.
However, most oil spills are not from oil spills. It comes from theflow awayof pollutants into streams and rivers that flow into the sea. Most of the runoff comes from individual consumers. Cars, buses, motorcycles and even lawn mowers spill oil and grease on roads, streets and highways. (Runoff makes busy roads shiny and sometimes slippery.)Gullysor creeks wash the runoff into local waterways that eventually empty into the ocean.
The largest US ocean oil spill happened in 1989 in Alaska by the tankerExxon Valdez. DieExxon Valdezat least 10 million gallons of oil ran into Prince William Sound. By comparison, American and Canadian consumers spill approximately 16 million gallons of oil runoff into the Atlantic and Pacific Oceans each year.
For centuries, humans have used the ocean as a dumping ground for wastesewageand other waste.
In the 21st century, waste includes not only oil but also chemical runoff from factories andAgriculture. These chemicals includeNitrateandPhosphate, which are often used asfertilizer. These chemicals encourage algal blooms. An algal bloom is an increase in algae and bacteria that threatens plants and other marine life. Algal blooms limit the amount of oxygen in a marine environment, resulting in so-called algal bloomstote Zonen, where little life exists beneath the sea surface. Algal blooms can spread hundreds or even thousands of kilometers.
Another source of pollution isplastics. Most of the marine litter, or garbage, is plastic discarded by consumers. Plastics such as water bottles, bags, six-pack rings and packaging material are hazardous to marine life. Marine animals are harmed by the plastic, either by becoming entangled in it or by eating it.
An example of marine pollution, which consists mainly of plastics, is theGreat Pacific Garbage Patch. The Great Pacific Garbage Patch is a floating garbage dump in the North Pacific. It's about twice the size of Texas and likely contains about 100 million tons of debris. Most of this debris originates from the west coast of North America (USA and Canada) and the east coast of Asia (Japan, China, Russia, North Korea and South Korea). Due to ocean currents and weather patterns, the patch is a relatively stable formation and contains new and dissipating debris. The smaller plastic debris is eaten by jellyfish or other organisms and then consumed by larger onespredatorsin the food web. These plastic chemicals can then enter a person's diet via fish or shellfish.
Another source of pollution is carbon dioxide. The ocean absorbs most of the carbon dioxide from the atmosphere. Carbon dioxide, which is necessary for life, is denoted as agreenhouse gasesand trapsradiationin the earth's atmosphere. Carbon dioxide forms many acids, calledcarbonic acids, in the ocean. Ocean ecosystems have adapted to the presence of certain levels of carbonic acid, but increases in carbon dioxide have led to increases in ocean acids. Thisocean acidificationerodes the shells of animals such as clams, crabs and corals.
Global warming contributes to rising sea temperatures andSea level.
Warmer oceans are radically changing the ecosystem. Global warming is causing cold-water habitats to shrink, meaning there is less room for animals like penguins, seals or whales. Plankton, the base of the ocean's food chain, thrive in cold water. As the water warms, marine life has less plankton to eat.
Meltglacierandice sheetscontribute tosea level rises. Rising sea levels threaten coastal ecosystems and property. River deltas and estuaries are at risk from flooding. The coasts are more likely to sufferErosion. Seawater is more likely to contaminate freshwater sources. All of these consequences – flooding, erosion, water pollution – put low-lying island nations like the Maldives in the Indian Ocean at high risk of disaster.
To find ways to protect the ocean from pollution and the effects of climate change, scientists from around the world are collaborating on studies of marine waters and marine life. They also work together to control pollution and limit global warming. Many countries are working to reach agreements on the management and use of marine resources.
Although the ocean is vast, it is more easily polluted and damaged than people once thought. It requires care and protection as well as expert management. Only then can it continue to provide the many resources that living beings—including humans—need.