Saline water (more commonly known as salt water ) is water that contains a high concentration of dissolved salts (mainly sodium chloride ). On the United States Geological Survey (USGS) salinity scale, saline water is saltier than brackish water , but less salty than brine . The salt concentration is usually expressed in parts per thousand (permille, ‰) and parts per million (ppm). The USGS salinity scale defines three levels of saline water. The salt concentration in slightly saline water is 1,000 to 3,000 ppm (0.1–0.3%); in moderately saline water is 3,000 to 10,000 ppm (0.3–1%); and in highly saline water is 10,000 to 35,000 ppm (1–3.5%). Seawater has a salinity of roughly 35,000 ppm, equivalent to 35 grams of salt per one liter (or kilogram) of water. The saturation level is only nominally dependent on the temperature of the water. At 20 °C (68 °F) one liter of water can dissolve about 357 grams of salt, a concentration of 26.3 percent by weight (% w/w). At 100 °C (212 °F) (the boiling temperature of pure water), the amount of salt that can be dissolved in one liter of water increases to about 391 grams, a concentration of 28.1% w/w.
84-398: The ocean 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
168-492: 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
252-430: A salinometer . Density ρ of brine at various concentrations and temperatures from 200 to 575 °C (392 to 1,067 °F) can be approximated with a linear equation: ρ [ l b / f t 3 ] = a 3 − ( a 2 ⋅ T [ F ] ) {\displaystyle \rho [lb/ft^{3}]=a_{3}-(a_{2}\cdot T[F])} where
336-595: 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
420-709: A moon of Saturn, and Triton , a moon of Neptune, have atmospheres mainly of nitrogen . When in the part of its orbit closest to the Sun, Pluto has an atmosphere of nitrogen and methane similar to Triton's, but these gases are frozen when it is farther from the Sun. Other bodies within the Solar System have extremely thin atmospheres not in equilibrium. These include the Moon ( sodium gas), Mercury (sodium gas), Europa (oxygen), Io ( sulfur ), and Enceladus ( water vapor ). The first exoplanet whose atmospheric composition
504-508: A planet from atmospheric escape and that for some magnetizations the presence of a magnetic field works to increase the escape rate. Other mechanisms that can cause atmosphere depletion are solar wind -induced sputtering, impact erosion, weathering , and sequestration—sometimes referred to as "freezing out"—into the regolith and polar caps . Atmospheres have dramatic effects on the surfaces of rocky bodies. Objects that have no atmosphere, or that have only an exosphere, have terrain that
588-454: 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
672-493: 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
756-451: A variable amount of water vapor is also present, on average about 1% at sea level. The low temperatures and higher gravity of the Solar System's giant planets — Jupiter , Saturn , Uranus and Neptune —allow them more readily to retain gases with low molecular masses . These planets have hydrogen–helium atmospheres, with trace amounts of more complex compounds. Two satellites of the outer planets possess significant atmospheres. Titan ,
840-402: 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
924-464: A wide range of velocities, there will always be some fast enough to produce a slow leakage of gas into space. Lighter molecules move faster than heavier ones with the same thermal kinetic energy , and so gases of low molecular weight are lost more rapidly than those of high molecular weight. It is thought that Venus and Mars may have lost much of their water when, after being photodissociated into hydrogen and oxygen by solar ultraviolet radiation,
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#17327646462131008-556: 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 , a boundary between less dense surface water and dense deep water. Saline water At 100 °C (212 °F; 373 K), saturated sodium chloride brine
1092-406: 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
1176-437: 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
1260-439: Is a layer of gases that envelop an astronomical object , held in place by the gravity of the object. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A stellar atmosphere is the outer region of a star, which includes the layers above the opaque photosphere ; stars of low temperature might have outer atmospheres containing compound molecules . The atmosphere of Earth
1344-463: Is about 28% salt by weight. At 0 °C (32 °F; 273 K), brine can only hold about 26% salt. At 20 °C one liter of water can dissolve about 357 grams of salt, a concentration of 26.3%. The thermal conductivity of seawater (3.5% dissolved salt by weight) is 0.6 W/mK at 25 °C (77 °F). The thermal conductivity decreases with increasing salinity and increases with increasing temperature. The salt content can be determined with
1428-741: 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
1512-444: 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
1596-414: Is composed of nitrogen (78%), oxygen (21%), argon (0.9%), carbon dioxide (0.04%) and trace gases. Most organisms use oxygen for respiration ; lightning and bacteria perform nitrogen fixation which produces ammonia that is used to make nucleotides and amino acids ; plants , algae , and cyanobacteria use carbon dioxide for photosynthesis . The layered composition of the atmosphere minimises
1680-423: Is covered in craters . Without an atmosphere, the planet has no protection from meteoroids , and all of them collide with the surface as meteorites and create craters. For planets with a significant atmosphere, most meteoroids burn up as meteors before hitting a planet's surface. When meteoroids do impact, the effects are often erased by the action of wind. Wind erosion is a significant factor in shaping
1764-411: 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
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#17327646462131848-416: 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 a halocline . If
1932-455: 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
2016-452: 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
2100-407: 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
2184-422: 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
2268-475: 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] ),
2352-401: Is the lowest layer of the atmosphere. This extends from the planetary surface to the bottom of the stratosphere . The troposphere contains 75–80% of the mass of the atmosphere, and is the atmospheric layer wherein the weather occurs; the height of the troposphere varies between 17 km at the equator and 7.0 km at the poles. The stratosphere extends from the top of the troposphere to
2436-688: 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
2520-480: 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
2604-590: 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
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2688-405: 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
2772-587: 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
2856-439: 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
2940-456: 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
3024-403: 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
3108-421: 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
3192-400: 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
3276-646: 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
3360-740: 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
3444-421: 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
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3528-477: 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)
3612-438: The atmosphere can transport thermal energy from the higher temperature interior up to the surface. From the perspective of a planetary geologist , the atmosphere acts to shape a planetary surface. Wind picks up dust and other particles which, when they collide with the terrain, erode the relief and leave deposits ( eolian processes). Frost and precipitations , which depend on the atmospheric composition, also influence
3696-411: The base of the exosphere at 690 km and contains the ionosphere , where solar radiation ionizes the atmosphere. The density of the ionosphere is greater at short distances from the planetary surface in the daytime and decreases as the ionosphere rises at night-time, thereby allowing a greater range of radio frequencies to travel greater distances. The exosphere begins at 690 to 1,000 km from
3780-428: The bottom of the mesosphere , and contains the ozone layer , at an altitude between 15 km and 35 km. It is the atmospheric layer that absorbs most of the ultraviolet radiation that Earth receives from the Sun. The mesosphere ranges from 50 km to 85 km and is the layer wherein most meteors are incinerated before reaching the surface. The thermosphere extends from an altitude of 85 km to
3864-407: 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):
3948-426: The diminishing mass of the gas above the point of barometric measurement. The units of air pressure are based upon the standard atmosphere (atm), which is 101,325 Pa (equivalent to 760 Torr or 14.696 psi ). The height at which the atmospheric pressure declines by a factor of e (an irrational number equal to 2.71828) is called the scale height ( H ). For an atmosphere of uniform temperature,
4032-431: The distance from the Sun determines the energy available to heat atmospheric gas to the point where some fraction of its molecules' thermal motion exceed the planet's escape velocity , allowing those to escape a planet's gravitational grasp. Thus, distant and cold Titan , Triton , and Pluto are able to retain their atmospheres despite their relatively low gravities. Since a collection of gas molecules may be moving at
4116-509: 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,
4200-407: 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
4284-508: The harmful effects of sunlight , ultraviolet radiation, solar wind , and cosmic rays and thus protects the organisms from genetic damage. The current composition of the atmosphere of the Earth is the product of billions of years of biochemical modification of the paleoatmosphere by living organisms. Atmospheres are clouds of gas bound to and engulfing an astronomical focal point of sufficiently dominating mass , adding to its mass, possibly escaping from it or collapsing into it. Because of
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#17327646462134368-442: The hydrogen escaped. Earth's magnetic field helps to prevent this, as, normally, the solar wind would greatly enhance the escape of hydrogen. However, over the past 3 billion years Earth may have lost gases through the magnetic polar regions due to auroral activity, including a net 2% of its atmospheric oxygen. The net effect, taking the most important escape processes into account, is that an intrinsic magnetic field does not protect
4452-420: 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
4536-478: 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
4620-737: 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
4704-431: The latter, such planetary nucleus can develop from interstellar molecular clouds or protoplanetary disks into rocky astronomical objects with varyingly thick atmospheres, gas giants or fusors . Composition and thickness is originally determined by the stellar nebula's chemistry and temperature, but can also by a product processes within the astronomical body outgasing a different atmosphere. The atmospheres of
4788-466: 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
4872-408: 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
4956-423: 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
5040-508: 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
5124-464: 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
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#17327646462135208-417: 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,
5292-416: 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
5376-431: 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,
5460-533: 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
5544-406: The past. The circulation of the atmosphere occurs due to thermal differences when convection becomes a more efficient transporter of heat than thermal radiation . On planets where the primary heat source is solar radiation, excess heat in the tropics is transported to higher latitudes. When a planet generates a significant amount of heat internally, such as is the case for Jupiter , convection in
5628-450: 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
5712-429: The planets Venus and Mars are principally composed of carbon dioxide and nitrogen , argon and oxygen . The composition of Earth's atmosphere is determined by the by-products of the life that it sustains. Dry air (mixture of gases) from Earth's atmosphere contains 78.08% nitrogen, 20.95% oxygen, 0.93% argon, 0.04% carbon dioxide, and traces of hydrogen, helium, and other "noble" gases (by volume), but generally
5796-418: 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,
5880-402: The primary component of Earth's hydrosphere and 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
5964-416: The relief. Climate changes can influence a planet's geological history. Conversely, studying the surface of the Earth leads to an understanding of the atmosphere and climate of other planets. For a meteorologist , the composition of the Earth's atmosphere is a factor affecting the climate and its variations. For a biologist or paleontologist , the Earth's atmospheric composition is closely dependent on
6048-468: The scale height is proportional to the atmospheric temperature and is inversely proportional to the product of the mean molecular mass of dry air, and the local acceleration of gravity at the point of barometric measurement. Surface gravity differs significantly among the planets. For example, the large gravitational force of the giant planet Jupiter retains light gases such as hydrogen and helium that escape from objects with lower gravity. Secondly,
6132-455: 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
6216-406: 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,
6300-401: 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,
6384-510: The surface to the ocean floor. The water column 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
6468-413: The surface, and extends to roughly 10,000 km, where it interacts with the magnetosphere of Earth. Atmospheric pressure is the force (per unit-area) perpendicular to a unit-area of planetary surface, as determined by the weight of the vertical column of atmospheric gases. In said atmospheric model, the atmospheric pressure , the weight of the mass of the gas, decreases at high altitude because of
6552-456: 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
6636-417: The terrain of rocky planets with atmospheres, and over time can erase the effects of both craters and volcanoes . In addition, since liquids cannot exist without pressure, an atmosphere allows liquid to be present at the surface, resulting in lakes , rivers and oceans . Earth and Titan are known to have liquids at their surface and terrain on the planet suggests that Mars had liquid on its surface in
6720-469: The values of a n are: About four percent of hydrogen gas produced worldwide is created by electrolysis . The majority of this hydrogen produced through electrolysis is a side product in the production of chlorine . [REDACTED] Media related to Saline water at Wikimedia Commons Atmosphere An atmosphere (from Ancient Greek ἀτμός ( atmós ) 'vapour, steam' and σφαῖρα ( sphaîra ) 'sphere')
6804-432: 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
6888-475: 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
6972-461: Was determined is HD 209458b , a gas giant with a close orbit around a star in the constellation Pegasus . Its atmosphere is heated to temperatures over 1,000 K, and is steadily escaping into space. Hydrogen, oxygen, carbon and sulfur have been detected in the planet's inflated atmosphere. The atmosphere of Earth is composed of layers with different properties, such as specific gaseous composition, temperature, and pressure. The troposphere
7056-771: 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
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