FACTOID # 6: Michigan is ranked 22nd in land area, but since 41.27% of the state is composed of water, it jumps to 11th place in total area.
 
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Encyclopedia > Underwater
An underwater scene just beneath the surface.
An underwater scene just beneath the surface.

Underwater is a term describing the realm below the surface of water where the water exists in a natural feature (called a body of water) such as an ocean, sea, lake, pond, or river. Three quarters of the planet Earth is covered by water. A majority of the planet's solid surface is abyssal plain, at depths between 4000 and 5500 m (13,000 to 18,000 ft) below the surface of the oceans. The solid surface location on the planet closest to the center of the orb is the Challenger Deep, located in the Mariana Trench at a depth of 10,924 m (35,838 ft) under the sea. The term underwater may refer to: Underwater – the realm below the surface of water. ... Image File history File links LightningVolt_Deep_Blue_Sea. ... Image File history File links LightningVolt_Deep_Blue_Sea. ... Impact from a water drop causes an upward rebound jet surrounded by circular capillary waves. ... Impact from a water drop causes an upward rebound jet surrounded by circular capillary waves. ... Animated map exhibiting the worlds oceanic waters. ... This article is about the body of water. ... For other uses, see Lake (disambiguation). ... Two people reflected in a fish pond A pond is typically a man made body of water smaller than a lake. ... For other uses, see River (disambiguation). ... This article is about Earth as a planet. ... Abyssal plains are flat or very gently sloping areas of the deep ocean basin floor. ... This article needs additional references or sources for verification. ... This article is about the geographical feature. ... To help compare different orders of magnitude this page lists lengths between 10 and 100 km (104 to 105 m). ...


Although a number of human activities are conducted underwater—such as scuba diving for work or recreation, or even underwater warfare with submarines—this very extensive environment on planet earth is hostile to humans in many ways and therefore little explored. This article is about modern humans. ... Scuba diving is swimming underwater while using self-contained breathing equipment. ... Professional diving is diving for payment. ... Recreational diving is a type of diving that uses SCUBA equipment for the purpose of leisure and enjoyment. ... Underwater warfare refers to combat conducted underwater such as: submarines actions and anti-submarine warfare, i. ... USS Los Angeles A submarine is a specialized watercraft that can operate underwater. ... This article is about Earth as a planet. ...


An immediate obstacle to human activity under water is the fact that human lungs cannot naturally function in this environment. Unlike the gills of fish, human lungs are adapted to the exchange of gases at atmospheric pressure, not liquids. Aside from simply having insufficient musculature to rapidly move water in and out of the lungs, a more significant problem for all air breathing animals, such as mammals and birds, is that water contains so little dissolved oxygen compared with atmospheric air. Air is around 21% O2; water typically is less than 0.001% dissolved oxygen. Human respiratory system The lungs flank the heart and great vessels in the chest cavity. ... For other uses, see Gill (disambiguation). ... For other uses, see Fish (disambiguation). ... Human respiratory system The lungs flank the heart and great vessels in the chest cavity. ... Gas can also refer to gasoline and natural gas and also hydrogen. ... This article is about pressure in the physical sciences. ... For other uses, see Liquid (disambiguation). ... Subclasses & Infraclasses Subclass †Allotheria* Subclass Prototheria Subclass Theria Infraclass †Trituberculata Infraclass Metatheria Infraclass Eutheria Mammals (class Mammalia) are warm-blooded, vertebrate animals characterized by the presence of sweat glands, including those that produce milk, and by the presence of: hair, three middle ear bones used in hearing, and a neocortex... For other uses, see Bird (disambiguation). ... General Name, symbol, number oxygen, O, 8 Chemical series nonmetals, chalcogens Group, period, block 16, 2, p Appearance colorless (gas) pale blue (liquid) Standard atomic weight 15. ... Look up air in Wiktionary, the free dictionary. ...


The density of water also causes problems that increase dramatically with depth. The air pressure at the planet surface is 101 kilopascals (14.7 lb. per sq. inch). A comparable water pressure occurs at a depth of only 10 m (34 ft.) (9.8 m (33 ft) for sea water) Thus, at about 10 m below the surface the water exerts twice the pressure (2 atmospheres or 200 kPa) on the body as air at surface level. For other uses, see Density (disambiguation). ... Diurnal (daily) rhythm of air pressure in northern Germany (black curve is air pressure) Atmospheric pressure is the pressure at any point in the Earths atmosphere. ... The pascal (symbol Pa) is the SI unit of pressure. ...


For solid objects like our bones and muscles, this added pressure is not much of a problem; but it is a problem for any air-filled spaces like the mouth, ears, paranasal sinuses and lungs. This is because the air in those spaces reduces in volume when under pressure and so does not provide those spaces with support from the higher outside pressure. Even at a depth of 8 feet (2.5 m) underwater, an inability to equalize air pressure in the middle ear with outside water pressure can cause pain, and the tympanic membrane can rupture at depths under 10 ft (3 m). The danger of pressure damage is greatest in shallow water because the rate of pressure change is greatest at the surface of the water. For example the pressure increase between the surface and 10 m (33 ft) is 100% (100 kPa to 200 kPa), but the pressure increase from 30 m (100 ft) to 40 m (130 ft) is only 25% (400 kPa to 500 kPa). For other uses, see Mouth (disambiguation). ... For other uses, see Ear (disambiguation). ... This article does not cite any references or sources. ... The middle ear is the portion of the ear internal to the eardrum, and external to the oval window of the cochlea. ... The tympanum or tympanic membrane, colloquially known as eardrum, is a thin membrane that separates the outer ear from the middle ear. ...


Any object immersed in water is provided with a buoyant force that counters the force of gravity, appearing to make the object less heavy. If the overall density of the object exceeds the density of water, the object sinks. If the overall density is less than the density of water, the object rises until it floats on the surface. In physics, buoyancy is the upward force on an object produced by the surrounding fluid (i. ... Gravity is a force of attraction that acts between bodies that have mass. ...

Note the bluish cast given to objects in this underwater photo of pillow lava. (NOAA)
Note the bluish cast given to objects in this underwater photo of pillow lava. (NOAA)

With increasing depth underwater, sunlight is absorbed, and the amount of visible light diminishes. Because absorption is greater for long wavelengths (red end of the visible spectrum) than for short wavelengths (blue end of the visible spectrum), the colour spectrum is rapidly altered with increasing depth. White objects at the surface appear bluish underwater, and red objects appear dark, even black. Although light penetration will be less if water is turbid, in the very clear water of the open ocean less than 25% of the surface light reaches a depth of 10 m (33 feet). At 100 m (330 ft) the light present from the sun is about 0.5% of that at the surface. Image ID: nur05018, National Undersearch Research Program (NURP) Collection Location: Hawaii Photo Date: 1988 July Credit: OAR/National Undersea Research Program (NURP) This NOAA image was previously uploaded as Image:Pillow lava small. ... Image ID: nur05018, National Undersearch Research Program (NURP) Collection Location: Hawaii Photo Date: 1988 July Credit: OAR/National Undersea Research Program (NURP) This NOAA image was previously uploaded as Image:Pillow lava small. ... Look up lava, Aa, pahoehoe in Wiktionary, the free dictionary. ... The National Oceanic and Atmospheric Administration (NOAA) is a scientific agency of the United States Department of Commerce focused on the conditions of the oceans and the atmosphere. ... Prism splitting light High Resolution Solar Spectrum Sunlight in the broad sense is the total spectrum of the electromagnetic radiation given off by the Sun. ... This article does not cite any references or sources. ... For other uses, see Wavelength (disambiguation). ... “Visible light” redirects here. ... The visible spectrum is the portion of the optical spectrum (light or electromagnetic spectrum) that is visible to the human eye. ... Turbidity standards of 5, 50, and 500 NTU Turbidity is a cloudiness or haziness of a fluid caused by individual particles (suspended solids) that are generally invisible to the naked eye, similar to smoke in air. ...


The euphotic depth is the depth at which light intensity falls to 1% of the value at the surface. This depth is dependent upon water clarity, being only a few meters underwater in a turbid estuary, but may reach 200 meters in the open ocean. At the euphotic depth, plants (such as phytoplankton) have no net energy gain from photosynthesis and thus cannot grow. The euphotic zone is the surface layer of the ocean where sufficient light is available for photosynthesis. ... Diagrams of some typical phytoplankton Phytoplankton are the autotrophic component of plankton. ...


At depths greater than a few hundred meters, the sun has little effect on water temperature, because the sun's energy has been absorbed by water at the surface. In the great depths of the ocean the water temperature is very cold. In fact, 75% of the water in the world ocean (the great depths) has a temperature between 0 °C and 2 °C.


Water conducts heat around twenty five times more efficiently than air. Hypothermia, a potentially fatal condition, occurs when the human body's core temperature falls below 35 °C. Insulating the body's warmth from water is the main purpose of diving suits and exposure suits when used in water temperatures below 25 °C. K value redirects here. ... Hypothermia is a condition in which an organisms temperature drops below that Required fOr normal metabolism and Bodily functionS. In warm-blooded animals, core [[body Temperature]] is maintained nEar a constant leVel through biologic [[homEostasis]]. But wheN the body iS exposed to cold Its internal mechanismS may be unable... Two divers, one wearing a 1 atmosphere diving suit and the other standard diving dress, preparing to explore the wreck of the RMS Lusitania, 1935 A diving suit is a garment or device designed to protect a diver from the underwater environment. ...


Sound is transmitted about 4.5 times faster in water (about 1435 m/s in fresh water) as it is in air (330 m/s). The human brain can determine the direction of sound in air by detecting small differences in the time it takes for sound waves in air to reach each of the two ears. For these reasons divers find it difficult to determine the direction of sound underwater. It is also impossible to shout underwater without drowning. Sound is a disturbance of mechanical energy that propagates through matter as a wave. ...


See also

Timeline of underwater technology // Pre-industrial Several centuries BC: (Relief carvings made at this time show Assyrian soldiers crossing rivers using inflated goatskin floats. ... Pink Anemonefish hiding in tentacles Underwater photography is the process of taking photographs while underwater. ... Underwater acoustics is the study of the propagation of sound in water and the interaction of the mechanical waves that constitute sound with the water and its boundaries. ...

References

  • Dueker, C. W. 1970, Medical aspects of sport diving. A.S. Barnes and Co., New York. 232 pp.
  • The Briny Deep – Oceanography notes at San Jose State University.

  Results from FactBites:
 
Underwater - Wikipedia, the free encyclopedia (930 words)
Underwater, sometimes shortened as U/W, is a term describing the realm below the surface of water where the water exists in a natural feature (called a body of water) such as an ocean, sea, lake, pond, or river.
The solid surface location on the planet closest to the center of the orb is the Challenger Deep, located in the Mariana Trench at a depth of 10,924 m (35,838 ft) under the sea.
With increasing depth underwater, sunlight is absorbed, and the amount of visible light diminishes.
underwater - definition of underwater in Encyclopedia (967 words)
The fact that human lungs cannot naturally function underwater is but one reason we cannot easily visit the underwater realm.
Because absorption is greater for long wavelengths (red end of the visible spectrum) than for short wavelengths (blue end of the visible spectrum), the color spectrum is rapidly altered with increasing depth.
Underwater (band) – a band formed in the late 1990s with Jeremy Wilkins and Melissa Mileski.
  More results at FactBites »

 
 

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