86-718: The Great Australian Bight is a large oceanic bight , or open bay, off the central and western portions of the southern coastline of mainland Australia . There are two definitions for its extent—one by the International Hydrographic Organization (IHO) and another by the Australian Hydrographic Service (AHS). The bight is generally considered part of the Indian Ocean , although the AHS classifies it as part of
172-410: A halocline . If a zone undergoes a strong, vertical chemistry gradient with depth, it contains a chemocline . Temperature and salinity control ocean water density. Colder and saltier water is denser, and this density plays a crucial role in regulating the global water circulation within the ocean. The halocline often coincides with the thermocline, and the combination produces a pronounced pycnocline ,
258-493: A mid-ocean ridge , which creates a long mountain range beneath the ocean. Together they form the global mid-oceanic ridge system that features the longest mountain range in the world. The longest continuous mountain range is 65,000 km (40,000 mi). This underwater mountain range is several times longer than the longest continental mountain range – the Andes . Oceanographers state that less than 20% of
344-479: A boundary between less dense surface water and dense deep water. Baxter Cliffs The Baxter Cliffs is a long stretch of coastal cliff on the south coast of Western Australia . The Baxter Cliffs are up to 80 metres high and extend for almost 200 kilometres along the coast, from Point Culver in the west, which marks the northern end of the Israelite Plain , northeastwards to Twilight Cove in
430-595: A gentle breeze on a pond causes ripples to form. A stronger gust blowing over the ocean causes larger waves as the moving air pushes against the raised ridges of water. The waves reach their maximum height when the rate at which they are travelling nearly matches the speed of the wind. In open water, when the wind blows continuously as happens in the Southern Hemisphere in the Roaring Forties , long, organized masses of water called swell roll across
516-455: A result, the photic zone is the most biodiverse and the source of the food supply which sustains most of the ocean ecosystem . Ocean photosynthesis also produces half of the oxygen in the Earth's atmosphere. Light can only penetrate a few hundred more meters; the rest of the deeper ocean is cold and dark (these zones are called mesopelagic and aphotic zones). The continental shelf is where
602-496: A shallow area and this, coupled with a low pressure system, can raise the surface of the ocean dramatically above a typical high tide. The average depth of the oceans is about 4 km. More precisely the average depth is 3,688 meters (12,100 ft). Nearly half of the world's marine waters are over 3,000 meters (9,800 ft) deep. "Deep ocean," which is anything below 200 meters (660 ft), covers about 66% of Earth's surface. This figure does not include seas not connected to
688-403: A wave-cut platform develops at the foot of the cliff and this has a protective effect, reducing further wave-erosion. Material worn from the margins of the land eventually ends up in the sea. Here it is subject to attrition as currents flowing parallel to the coast scour out channels and transport sand and pebbles away from their place of origin. Sediment carried to the sea by rivers settles on
774-576: A worst-case scenario leak of oil could have a catastrophic effect on the southern coastline of Australia. The Australian Senate commenced an inquiry into oil or gas production in the Great Australian Bight on 22 February 2016. The committee was reestablished on 13 September 2016 following the Australian Federal Election. In October 2017, Chevron withdrew from the project, but it returned alongside BP in 2019. Though
860-406: A zone undergoes dramatic changes in temperature with depth, it contains a thermocline , a distinct boundary between warmer surface water and colder deep water. In tropical regions, the thermocline is typically deeper compared to higher latitudes. Unlike polar waters , where solar energy input is limited, temperature stratification is less pronounced, and a distinct thermocline is often absent. This
946-439: Is a bay , a small bay with a narrow inlet is a cove and a large bay may be referred to as a gulf . Coastlines are influenced by several factors including the strength of the waves arriving on the shore, the gradient of the land margin, the composition and hardness of the coastal rock, the inclination of the off-shore slope and the changes of the level of the land due to local uplift or submergence. Normally, waves roll towards
SECTION 10
#17327655599101032-719: Is a former seabed, uplifted during the Miocene . Consisting of limestone, it is very flat, and has an arid or semi-arid climate with very little rainfall, and high summer temperatures and high evaporation rates. It has no surface drainage, but has a karst drainage system through cave formation in the underlying limestone. North of the Nullarbor lies the Great Victoria Desert , which has an internal drainage system terminating in numerous small salt lakes . The lack of surface runoff and terrestrial nutrients results in
1118-743: Is about −2 °C (28 °F). In all parts of the ocean, deep ocean temperatures range between −2 °C (28 °F) and 5 °C (41 °F). Constant circulation of water in the ocean creates ocean currents . Those currents are caused by forces operating on the water, such as temperature and salinity differences, atmospheric circulation (wind), and the Coriolis effect . Tides create tidal currents, while wind and waves cause surface currents. The Gulf Stream , Kuroshio Current , Agulhas Current and Antarctic Circumpolar Current are all major ocean currents. Such currents transport massive amounts of water, gases, pollutants and heat to different parts of
1204-444: Is an important reference point for oceanography and geography, particularly as mean sea level . The ocean surface has globally little, but measurable topography , depending on the ocean's volumes. The ocean surface is a crucial interface for oceanic and atmospheric processes. Allowing interchange of particles, enriching the air and water, as well as grounds by some particles becoming sediments . This interchange has fertilized life in
1290-520: Is an outcrop of the granitic Gawler Craton . The Great Australian Bight was first encountered by European explorers in 1627 when Dutch navigator François Thijssen sailed along its western margins. The coast was later first accurately charted by the English navigator Matthew Flinders in 1802, during his circumnavigation of the Australian continent . A later land-based survey was accomplished by
1376-411: Is customarily divided into five principal oceans – listed below in descending order of area and volume: The ocean fills Earth's oceanic basins . Earth's oceanic basins cover different geologic provinces of Earth's oceanic crust as well as continental crust . As such it covers mainly Earth's structural basins , but also continental shelfs . In mid-ocean, magma is constantly being thrust through
1462-399: Is due to the fact that surface waters in polar latitudes are nearly as cold as deeper waters. Below the thermocline, water everywhere in the ocean is very cold, ranging from −1 °C to 3 °C. Because this deep and cold layer contains the bulk of ocean water, the average temperature of the world ocean is 3.9 °C. If a zone undergoes dramatic changes in salinity with depth, it contains
1548-463: Is further divided into zones based on depth and the amount of light present. The photic zone starts at the surface and is defined to be "the depth at which light intensity is only 1% of the surface value" (approximately 200 m in the open ocean). This is the zone where photosynthesis can occur. In this process plants and microscopic algae (free floating phytoplankton ) use light, water, carbon dioxide, and nutrients to produce organic matter. As
1634-456: Is irregular, unevenly dominating the Earth's surface . This leads to the distinction of the Earth's surface into a water and land hemisphere , as well as the division of the ocean into different oceans. Seawater covers about 361,000,000 km (139,000,000 sq mi) and the ocean's furthest pole of inaccessibility , known as " Point Nemo ", in a region known as spacecraft cemetery of
1720-655: Is listed as ‘endangered’ under the Commonwealth Environment Protection and Biodiversity Conservation Act 1999, breeds at the Head of Bight during winter. The Australian sea lion ( Neophoca cinerea ), which is endemic to Australia and is currently listed as “near threatened”, breeds in small colonies along the cliffs of the GAB." These marine mammals require this habitat to remain in existence, which has been recognised by Australian law. One location on
1806-462: Is needed to fully understand the region's complex ecosystems and the potential impacts of human activities, such as resource extraction. Southern bluefin tuna are a popular fishing target in the Bight, and there have been attempts to explore the area for oil and gas since the 1960s. However, these proposals have faced significant opposition due to the potential environmental impacts. Two definitions of
SECTION 20
#17327655599101892-454: Is produced and magma is forced up creating underwater mountains, some of which may form chains of volcanic islands near to deep trenches. Near some of the boundaries between the land and sea, the slightly denser oceanic plates slide beneath the continental plates and more subduction trenches are formed. As they grate together, the continental plates are deformed and buckle causing mountain building and seismic activity. Every ocean basin has
1978-407: Is pushed across the surface of the ocean by the wind, but this represents a transfer of energy and not horizontal movement of water. As waves approach land and move into shallow water , they change their behavior. If approaching at an angle, waves may bend ( refraction ) or wrap around rocks and headlands ( diffraction ). When the wave reaches a point where its deepest oscillations of the water contact
2064-423: Is reflected back out of the water. Red light is most easily absorbed and thus does not reach great depths, usually to less than 50 meters (164 ft). Blue light, in comparison, can penetrate up to 200 meters (656 ft). Second, water molecules and very tiny particles in ocean water preferentially scatter blue light more than light of other colors. Blue light scattering by water and tiny particles happens even in
2150-480: Is sometimes referred to as the World Ocean, global ocean or the great ocean . The concept of a continuous body of water with relatively unrestricted exchange between its components is critical in oceanography . The word ocean comes from the figure in classical antiquity , Oceanus ( / oʊ ˈ s iː ə n ə s / ; ‹See Tfd› Greek : Ὠκεανός Ōkeanós , pronounced [ɔːkeanós] ),
2236-442: Is the body of salt water that covers approximately 70.8% of Earth . In English , the term ocean also refers to any of the large bodies of water into which the world ocean is conventionally divided. The following names describe five different areas of the ocean: Pacific , Atlantic , Indian , Antarctic/Southern , and Arctic . The ocean contains 97% of Earth's water and is the primary component of Earth's hydrosphere and
2322-400: Is thereby essential to life on Earth. The ocean influences climate and weather patterns, the carbon cycle , and the water cycle by acting as a huge heat reservoir . Ocean scientists split the ocean into vertical and horizontal zones based on physical and biological conditions. The pelagic zone is the open ocean's water column from the surface to the ocean floor. The water column
2408-673: The National Offshore Petroleum Safety and Environmental Management Authority approved exploration plans in late 2019, Equinor withdrew from the project in February 2020, citing profitability reasons. The settlements existing along the coastline of the bight, such as Ceduna and Eucla have facilities to access the bight. Some other locations on the Eyre Highway or located on the Nullarbor do not have facilities or easy access. Ocean The ocean
2494-691: The North Sea or the Red Sea . There is no sharp distinction between seas and oceans, though generally seas are smaller, and are often partly (as marginal seas ) or wholly (as inland seas ) bordered by land. The contemporary concept of the World Ocean was coined in the early 20th century by the Russian oceanographer Yuly Shokalsky to refer to the continuous ocean that covers and encircles most of Earth. The global, interconnected body of salt water
2580-481: The South Pacific Ocean , at 48°52.6′S 123°23.6′W / 48.8767°S 123.3933°W / -48.8767; -123.3933 ( Point Nemo ) . This point is roughly 2,688 km (1,670 mi) from the nearest land. There are different customs to subdivide the ocean and are adjourned by smaller bodies of water such as, seas , gulfs , bays , bights , and straits . The ocean
2666-643: The Southern Ocean . Its coastline is characterized by cliff faces and rocky capes, making it an ideal location for whale-watching. This oceanic feature was first encountered by European explorers in 1627, and was accurately charted by English navigator Matthew Flinders in 1802. The Great Australian Bight came into existence about 50 million years ago when the supercontinent Gondwana broke apart, separating Antarctica from Australia . The Bight's waters are highly biodiverse , especially in zooplankton , due to specific ocean currents. However, more research
Great Australian Bight - Misplaced Pages Continue
2752-592: The Thames Barrier is designed to protect London from a storm surge, while the failure of the dykes and levees around New Orleans during Hurricane Katrina created a humanitarian crisis in the United States. Most of the ocean is blue in color, but in some places the ocean is blue-green, green, or even yellow to brown. Blue ocean color is a result of several factors. First, water preferentially absorbs red light, which means that blue light remains and
2838-406: The coastline and structure of the world ocean. A global ocean has existed in one form or another on Earth for eons. Since its formation the ocean has taken many conditions and shapes with many past ocean divisions and potentially at times covering the whole globe. During colder climatic periods, more ice caps and glaciers form, and enough of the global water supply accumulates as ice to lessen
2924-591: The ocean floor , they begin to slow down. This pulls the crests closer together and increases the waves' height , which is called wave shoaling . When the ratio of the wave's height to the water depth increases above a certain limit, it " breaks ", toppling over in a mass of foaming water. This rushes in a sheet up the beach before retreating into the ocean under the influence of gravity. Earthquakes , volcanic eruptions or other major geological disturbances can set off waves that can lead to tsunamis in coastal areas which can be very dangerous. The ocean's surface
3010-644: The 600 fish species that occur in southern Australia have been recorded in SA. Several species, including the coastal stingaree ( Urolophus orarius ) and crested threefin ( Trinorfolkia cristata ), are restricted to South Australia and occur in the GAB. The patterns of distribution and abundance of fishes in the GAB are poorly understood." There are some clear findings from the review, "The GAB provides critical habitat for two species of marine mammals that are recognised internationally as being priorities for conservation. The southern right whale ( Eubalaena australis ), which
3096-486: The Bight . At Head of the Bight the escarpment turns inland to the northeast. The coastline of the western Eyre Peninsula is characterised by rocky capes, bays, and islands, including Fowlers Bay , Smoky Bay , Streaky Bay , and the Nuyts Archipelago . The coastline is formed from aeolianite limestone. Waves and currents have formed beaches and dunes from eroded aeolianite sand. The southern Eyre peninsula
3182-442: The Earth's biosphere . Oceanic evaporation , as a phase of the water cycle, is the source of most rainfall (about 90%), causing a global cloud cover of 67% and a consistent oceanic cloud cover of 72%. Ocean temperatures affect climate and wind patterns that affect life on land. One of the most dramatic forms of weather occurs over the oceans: tropical cyclones (also called "typhoons" and "hurricanes" depending upon where
3268-512: The East. A line from Cape Otway , Victoria to King Island and thence to Cape Grim , the northwest extreme of Tasmania. The AHS defines the bight with a smaller area, from Cape Pasley , Western Australia , to Cape Carnot , South Australia - a distance of 1,160 kilometres (720 mi). Much of the bight lies due south of the expansive Nullarbor Plain , which straddles South Australia and Western Australia. The Eyre Highway passes close to
3354-485: The English explorer Edward John Eyre . The bight came into existence when Gondwana broke apart and separated Antarctica from Australia around 50 million years ago. The coastline of the Great Australian Bight is characterised by cliff faces (up to 60 metres or 200 feet high), surfing beaches and rock platforms, ideal for whale-watching . This is a popular activity during the southern hemisphere winter, when increasing numbers of southern right whales migrate to
3440-487: The GAB annually to feed on these rich pelagic resources." As the nutrients are swept up from the deep water ocean floor and pushed in towards the coast, the food chain is injected with a massive influx of the bottom rung. There is not enough known about the full scope of species that dwell in or migrate to the Great Australian Bight, so more studies are required. "The Interim Marine and Coastal Regionalisation of Australia (IMCRA) classification suggests that high biodiversity in
3526-432: The GAB may be explained by the presence of temperate species with eastern and western affinities, as well as “tropical stragglers” from northern regions. However, patterns of diversity vary between taxa. Mangroves are poorly represented due to the lack of estuaries. Seagrasses are confined mainly to sheltered bays and the lees of reefs and islands due to the frequent disturbance of inshore habitats by large swells. In contrast,
Great Australian Bight - Misplaced Pages Continue
3612-575: The Great Australian Bight are highly biodiverse, particularly in zooplankton, due to a particular series of ocean currents. A literature review undertaken by SARDI (South Australian Research and Development Institute) on the Benthic Protection Zone of the Great Australian Bight Marine Park in 2003 states: "Upwelling events during summer and autumn produce cool patches of surface water along the coast of
3698-456: The Moon are 20x stronger than the Moon's tidal forces on the Earth.) The primary effect of lunar tidal forces is to bulge Earth matter towards the near and far sides of the Earth, relative to the moon. The "perpendicular" sides, from which the Moon appears in line with the local horizon, experience "tidal troughs". Since it takes nearly 25 hours for the Earth to rotate under the Moon (accounting for
3784-403: The Moon's 28 day orbit around Earth), tides thus cycle over a course of 12.5 hours. However, the rocky continents pose obstacles for the tidal bulges, so the timing of tidal maxima may not actually align with the Moon in most localities on Earth, as the oceans are forced to "dodge" the continents. Timing and magnitude of tides vary widely across the Earth as a result of the continents. Thus, knowing
3870-471: The Moon's gravity, oceanic tides are also substantially modulated by the Sun's tidal forces, by the rotation of the Earth, and by the shape of the rocky continents blocking oceanic water flow. (Tidal forces vary more with distance than the "base" force of gravity: the Moon's tidal forces on Earth are more than double the Sun's, despite the latter's much stronger gravitational force on Earth. Earth's tidal forces upon
3956-400: The Moon's position does not allow a local to predict tide timings, instead requiring precomputed tide tables which account for the continents and the Sun, among others. During each tidal cycle, at any given place the tidal waters rise to maximum height, high tide, before ebbing away again to the minimum level, low tide. As the water recedes, it gradually reveals the foreshore , also known as
4042-648: The Okeanos is represented with a dragon-tail on some early Greek vases. Scientists believe that a sizable quantity of water would have been in the material that formed Earth. Water molecules would have escaped Earth's gravity more easily when it was less massive during its formation. This is called atmospheric escape . During planetary formation , Earth possibly had magma oceans . Subsequently, outgassing , volcanic activity and meteorite impacts , produced an early atmosphere of carbon dioxide , nitrogen and water vapor , according to current theories. The gases and
4128-741: The World Ocean, such as the Caspian Sea . The deepest region of the ocean is at the Mariana Trench , located in the Pacific Ocean near the Northern Mariana Islands . The maximum depth has been estimated to be 10,971 meters (35,994 ft). The British naval vessel Challenger II surveyed the trench in 1951 and named the deepest part of the trench the " Challenger Deep ". In 1960, the Trieste successfully reached
4214-421: The amounts in other parts of the water cycle. The reverse is true during warm periods. During the last ice age, glaciers covered almost one-third of Earth's land mass with the result being that the oceans were about 122 m (400 ft) lower than today. During the last global "warm spell," about 125,000 years ago, the seas were about 5.5 m (18 ft) higher than they are now. About three million years ago
4300-479: The atmosphere are thought to have accumulated over millions of years. After Earth's surface had significantly cooled, the water vapor over time would have condensed, forming Earth's first oceans. The early oceans might have been significantly hotter than today and appeared green due to high iron content. Geological evidence helps constrain the time frame for liquid water existing on Earth. A sample of pillow basalt (a type of rock formed during an underwater eruption)
4386-480: The bight that is specifically oriented towards the understanding of the natural history on its coastline is the Eyre Bird Observatory . Economically, the Bight has been exploited over many years as part of the fishing, whaling and shellfish industries. Southern bluefin tuna have been a favoured target of fishing in the Bight. Exploration for oil and gas in the Great Australian Bight first began in
SECTION 50
#17327655599104472-655: The bight with the Indian Ocean, while Bass Strait and the Tasman Sea are included by IHO with the South Pacific Ocean in the 2002 draft. In the 1953 edition, IHO includes Bass Strait as part of the Indian Ocean. The area around Cape Pasley is an eastern outcrop of the ancient crystalline rocks of the Yilgarn Craton . From there the coast curves north-eastwards, with an escarpment parallel to
4558-407: The bottom of the trench, manned by a crew of two men. Oceanographers classify the ocean into vertical and horizontal zones based on physical and biological conditions. The pelagic zone consists of the water column of the open ocean, and can be divided into further regions categorized by light abundance and by depth. The ocean zones can be grouped by light penetration into (from top to bottom):
4644-417: The cliffs of the bight between the Head of the Bight and Eucla . Outside of Australia, the Great Australian Bight is generally considered part of the Indian Ocean . The AHS considers it to be part of the Southern Ocean , using the expanded Australian definition used for this ocean. The IHO in its Limits of Oceans and Seas (both the currently in-force 1953 edition and the 2002 never-approved draft) includes
4730-565: The coast, reaching about 35 km (22 mi) inland at their widest point. There are extensive dunefields near the shore, some bare of vegetation, and others stabilized by coastal strand vegetation, shrubland, and mallee woodland. Near Eucla and the Western Australia–South Australia border the escarpment reaches the coast again, and the Bunda Cliffs or Nullarbor Cliffs extend for 220 km (140 mi) to Head of
4816-600: The coast. The Israelite Plain lies between the escarpment, here called the Wylie Scarp, and the shore, with a chain of coastal lagoons behind coastal dunes. As the coast turns eastwards the escarpment meets the shore, creating the Baxter Cliffs which extend for 200 km (120 mi). Near Cocklebiddy the escarpment curves inland again. Here the Roe Plains extends for about 300 km (190 mi) along
4902-670: The east, which is the transition from the cliffs to the coastal Roe Plains . Toolinna Cove is the only place along the Baxter Cliffs where a boat can be landed. The Baxter Cliffs are part of a long erosional escarpment which extends east and west across the Eucla Basin sedimentary formation. Other portions of the escarpment include the Hampton Tableland north of the Roe Plains, and the Bunda Cliffs east of
4988-509: The elder of the Titans in classical Greek mythology . Oceanus was believed by the ancient Greeks and Romans to be the divine personification of an enormous river encircling the world. The concept of Ōkeanós has an Indo-European connection. Greek Ōkeanós has been compared to the Vedic epithet ā-śáyāna-, predicated of the dragon Vṛtra-, who captured the cows/rivers. Related to this notion,
5074-661: The extent are in use – one used by the International Hydrographic Organization (IHO) and the other used by the Australian Hydrographic Service (AHS). The IHO defines the Great Australian Bight as having the following limits: On the North. The south coast of the Australian mainland. On the South. A line joining West Cape Howe ( 35°08′S 117°37′E / 35.133°S 117.617°E / -35.133; 117.617 ) Australia to South West Cape , Tasmania . On
5160-412: The formation of unusually high rogue waves . Most waves are less than 3 m (10 ft) high and it is not unusual for strong storms to double or triple that height. Rogue waves, however, have been documented at heights above 25 meters (82 ft). The top of a wave is known as the crest, the lowest point between waves is the trough and the distance between the crests is the wavelength. The wave
5246-421: The interface between water and air is called swell – a term used in sailing , surfing and navigation . These motions profoundly affect ships on the surface of the ocean and the well-being of people on those ships who might suffer from sea sickness . Wind blowing over the surface of a body of water forms waves that are perpendicular to the direction of the wind. The friction between air and water caused by
SECTION 60
#17327655599105332-482: The intertidal zone. The difference in height between the high tide and low tide is known as the tidal range or tidal amplitude. When the sun and moon are aligned (full moon or new moon), the combined effect results in the higher "spring tides", while the sun and moon misaligning (half moons) result in lesser tidal ranges. In the open ocean tidal ranges are less than 1 meter, but in coastal areas these tidal ranges increase to more than 10 meters in some areas. Some of
5418-739: The largest tidal ranges in the world occur in the Bay of Fundy and Ungava Bay in Canada, reaching up to 16 meters. Other locations with record high tidal ranges include the Bristol Channel between England and Wales, Cook Inlet in Alaska, and the Río Gallegos in Argentina. Tides are not to be confused with storm surges , which can occur when high winds pile water up against the coast in
5504-428: The late 1960s. Several oil majors — BP , Statoil/Equinor , and Chevron — proposed plans to drill exploration wells in the southern part of the area from 2017 onwards. On 11 October 2016, BP withdrew its plans to explore the area stating that it was not competitive and did not align with BP's strategic goals. The proposal to explore in the bight was the focus of community opposition. The Wilderness Society showed that
5590-486: The macroalgal assemblage of the GAB is one of the world's most diverse and includes >1200 species. Over 90% of species in most invertebrate groups are endemic to southern Australia, but the proportion that is confined to the GAB is unknown." There is still much research needed to fully understand the complex ecosystems of the Great Australian Bight and how any resource extraction or other human activity may affect them. The Literature review also states: "Approximately 370 of
5676-471: The majority of Earth's surface. It includes the Pacific , Atlantic , Indian , Southern/Antarctic , and Arctic oceans. As a general term, "the ocean" and "the sea" are often interchangeable. Strictly speaking, a "sea" is a body of water (generally a division of the world ocean) partly or fully enclosed by land. The word "sea" can also be used for many specific, much smaller bodies of seawater, such as
5762-408: The ocean faces many environmental threats, such as marine pollution , overfishing , and the effects of climate change . Those effects include ocean warming , ocean acidification and sea level rise . The continental shelf and coastal waters are most affected by human activity. The terms "the ocean" or "the sea" used without specification refer to the interconnected body of salt water covering
5848-423: The ocean meets dry land. It is more shallow, with a depth of a few hundred meters or less. Human activity often has negative impacts on marine life within the continental shelf. Ocean temperatures depend on the amount of solar radiation reaching the ocean surface. In the tropics, surface temperatures can rise to over 30 °C (86 °F). Near the poles where sea ice forms, the temperature in equilibrium
5934-508: The ocean, on land and air. All these processes and components together make up ocean surface ecosystems . Tides are the regular rise and fall in water level experienced by oceans, primarily driven by the Moon 's gravitational tidal forces upon the Earth. Tidal forces affect all matter on Earth, but only fluids like the ocean demonstrate the effects on human timescales. (For example, tidal forces acting on rock may produce tidal locking between two planetary bodies.) Though primarily driven by
6020-469: The ocean. If the wind dies down, the wave formation is reduced, but already-formed waves continue to travel in their original direction until they meet land. The size of the waves depends on the fetch , the distance that the wind has blown over the water and the strength and duration of that wind. When waves meet others coming from different directions, interference between the two can produce broken, irregular seas. Constructive interference can lead to
6106-419: The oceans absorb CO 2 from the atmosphere , a higher concentration leads to ocean acidification (a drop in pH value ). The ocean provides many benefits to humans such as ecosystem services , access to seafood and other marine resources , and a means of transport . The ocean is known to be the habitat of over 230,000 species , but may hold considerably more – perhaps over two million species. Yet,
6192-425: The oceans could have been up to 50 m (165 ft) higher. The entire ocean, containing 97% of Earth's water, spans 70.8% of Earth 's surface, making it Earth's global ocean or world ocean . This makes Earth, along with its vibrant hydrosphere a "water world" or " ocean world ", particularly in Earth's early history when the ocean is thought to have possibly covered Earth completely. The ocean's shape
6278-434: The oceans have been mapped. The zone where land meets sea is known as the coast , and the part between the lowest spring tides and the upper limit reached by splashing waves is the shore . A beach is the accumulation of sand or shingle on the shore. A headland is a point of land jutting out into the sea and a larger promontory is known as a cape . The indentation of a coastline, especially between two headlands,
6364-537: The oceans may have always been on the Earth since the beginning of the planet's formation. In this model, atmospheric greenhouse gases kept the oceans from freezing when the newly forming Sun had only 70% of its current luminosity . The origin of Earth's oceans is unknown. Oceans are thought to have formed in the Hadean eon and may have been the cause for the emergence of life . Plate tectonics , post-glacial rebound , and sea level rise continually change
6450-451: The photic zone, the mesopelagic zone and the aphotic deep ocean zone: The pelagic part of the aphotic zone can be further divided into vertical regions according to depth and temperature: Distinct boundaries between ocean surface waters and deep waters can be drawn based on the properties of the water. These boundaries are called thermoclines (temperature), haloclines (salinity), chemoclines (chemistry), and pycnoclines (density). If
6536-418: The power of a storm wave impacting on the foot of a cliff has a shattering effect as air in cracks and crevices is compressed and then expands rapidly with release of pressure. At the same time, sand and pebbles have an erosive effect as they are thrown against the rocks. This tends to undercut the cliff, and normal weathering processes such as the action of frost follows, causing further destruction. Gradually,
6622-475: The region from their summer feeding grounds in the Antarctic. The whales come to the Bight region, especially to the Head of Bight , to calve and breed, and do not feed until they return to the Antarctic. Their numbers were severely depleted by whaling, particularly during the 19th century, but have since recovered to some extent. The Nullarbor Plain , which borders much of the length of the Bight's coastline,
6708-501: The relatively shallow waters of the Great Australian Bight being generally low in nutrients, and therefore oligotrophic , compared with many other continental shelves which support major fisheries . Seasonal upwelling of deep ocean water along the coast of the Eyre Peninsula in the eastern part of the Bight brings nutrients to the surface waters, with the resulting fertility creating an important marine hotspot. The waters of
6794-455: The seabed between adjoining plates to form mid-oceanic ridges and here convection currents within the mantle tend to drive the two plates apart. Parallel to these ridges and nearer the coasts, one oceanic plate may slide beneath another oceanic plate in a process known as subduction . Deep trenches are formed here and the process is accompanied by friction as the plates grind together. The movement proceeds in jerks which cause earthquakes, heat
6880-407: The seabed causing deltas to form in estuaries. All these materials move back and forth under the influence of waves, tides and currents. Dredging removes material and deepens channels but may have unexpected effects elsewhere on the coastline. Governments make efforts to prevent flooding of the land by the building of breakwaters , seawalls , dykes and levees and other sea defences. For instance,
6966-401: The shore at the rate of six to eight per minute and these are known as constructive waves as they tend to move material up the beach and have little erosive effect. Storm waves arrive on shore in rapid succession and are known as destructive waves as the swash moves beach material seawards. Under their influence, the sand and shingle on the beach is ground together and abraded. Around high tide,
7052-522: The southern Eyre Peninsula. These patches contain elevated nutrient concentrations and support enhanced levels of primary productivity. High densities of zooplankton to the northwest of the patches indicate that the prevailing southeasterly winds transport the products of this enhanced biological production into the central GAB. These plankton communities support the highest densities of small planktivorous fishes, including sardine and anchovy, in Australian waters. Juvenile southern bluefin tuna (SBT) migrate into
7138-456: The system forms). As the world's ocean is the principal component of Earth's hydrosphere , it is integral to life on Earth, forms part of the carbon cycle and water cycle , and – as a huge heat reservoir – influences climate and weather patterns. The motions of the ocean surface, known as undulations or wind waves , are the partial and alternate rising and falling of the ocean surface. The series of mechanical waves that propagate along
7224-434: The very clearest ocean water, and is similar to blue light scattering in the sky . Ocean water represents the largest body of water within the global water cycle (oceans contain 97% of Earth's water ). Evaporation from the ocean moves water into the atmosphere to later rain back down onto land and the ocean. Oceans have a significant effect on the biosphere . The ocean as a whole is thought to cover approximately 90% of
7310-476: The world, and from the surface into the deep ocean. All this has impacts on the global climate system . Ocean water contains dissolved gases, including oxygen , carbon dioxide and nitrogen . An exchange of these gases occurs at the ocean's surface. The solubility of these gases depends on the temperature and salinity of the water. The carbon dioxide concentration in the atmosphere is rising due to CO 2 emissions , mainly from fossil fuel combustion. As
7396-775: Was recovered from the Isua Greenstone Belt and provides evidence that water existed on Earth 3.8 billion years ago. In the Nuvvuagittuq Greenstone Belt , Quebec , Canada, rocks dated at 3.8 billion years old by one study and 4.28 billion years old by another show evidence of the presence of water at these ages. If oceans existed earlier than this, any geological evidence either has yet to be discovered, or has since been destroyed by geological processes like crustal recycling . However, in August 2020, researchers reported that sufficient water to fill
#909090