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Phreatic is a term used in hydrology to refer to aquifers, in speleology to refer to cave passages, and in volcanology to refer to a type of volcanic eruption.
The term phreatic (the word originates from the Greekphrear, phreat- meaning "well" or "spring") is used in hydrology and the earth sciences to refer to matters relating to ground water (an aquifer) below the water table. The term 'phreatic surface' indicates the location where the pore water pressure is under atmospheric conditions (i.e. the pressure head is zero). This surface normally coincides with the water table. The slope of the phreatic surface is assumed to indicate the direction of ground water movement in an unconfined aquifer.
The phreatic zone, below the phreatic surface where rock and soil is saturated with water, is the counterpart of the vadose zone, or unsaturated zone, above. Unconfined aquifers are also referred to as phreatic aquifers because their upper boundary is provided by the phreatic surface.
Speleologyedit
In speleogenesis, a division of speleology, 'phreatic action' forms cave passages by dissolving the limestone in all directions,[1] as opposed to 'vadose action', whereby a stream running in a cave passage erodes a trench in the floor.[2] It occurs when the passage is full of water, and therefore normally only when it is below the water table, and only if the water is not saturated with calcium carbonate or calcium magnesium carbonate. A cave passage formed in this way is characteristically circular or oval in cross-section as limestone is dissolved on all surfaces.[3]
Many cave passages are formed by a combination of phreatic followed by vadose action. Such passages form a keyhole cross section: a round-shaped section at the top and a rectangular trench at the bottom.
A phreatic eruption or steam-blast eruption occurs when magma heats ground or surface water.
Biologyedit
Animals living within the phreatic zone of groundwater aquifers can be referred to as phreatobites.[4] They are usually isopod or amphipod crustaceans such as species of Stygobromus, though there is also a genus of snails (Phreatodrobia) and Phreatobius are a genus of catfish living within flooded leaf litter. Alternative descriptions for such animals include stygobite,[5]troglobite or Interstitial animals, as they live in water between the particles of the flooded substrate. They usually exhibit troglomorphism, with a loss of colour and eyesight, like the familiar blind cavefish which may also be referred to as 'phreatic fish'.
Such animals can often be found in wells, where human pursuit of water has dug down into their habitat.
See alsoedit
Phreatic zone – Zone in an aquifer below the water table
Vadose zone – Unsaturated aquifer above the water table
Water content – Quantity of water contained in a material
^New Mexico: Bureau of Mines & Mining Bulletin 117 (Part I: Discussion of Deposits and Events)
^"Glossary of Cave-Related Terms". Upper Cumberland Grotto Home Cave. Retrieved 13 November 2010.
^John A. Webb & Stanley Lithco (September 2001). Use of water chemistry to identify flow conduits in the porous Gambier Limestone, southeast Australia(PDF). 7th Conference on Limestone Hydrology and Fissured Media. France: Universite de Franche-Comte, Sciences & Techniques de l'Environnement. pp. 333–336. ISBN2-905226-14-5. Retrieved 13 November 2010. Passages are usually narrow vertical fissures, but phreatic tubes, circular or oval in cross-section, are present in some caves...[permanent dead link]
^"Glossary : Phreatobite". Speleogenesis. UIS Commission on Karst Hydrogeology and Speleogenesis.
^"Glossary : Stygobite". Speleogenesis. UIS Commission on Karst Hydrogeology and Speleogenesis.
External linksedit
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phreatic, look, phreatic, wiktionary, free, dictionary, term, used, hydrology, refer, aquifers, speleology, refer, cave, passages, volcanology, refer, type, volcanic, eruption, contents, hydrology, speleology, volcanology, biology, also, references, external, . Look up phreatic in Wiktionary the free dictionary Phreatic is a term used in hydrology to refer to aquifers in speleology to refer to cave passages and in volcanology to refer to a type of volcanic eruption Contents 1 Hydrology 2 Speleology 3 Volcanology 4 Biology 5 See also 6 References 7 External linksHydrology editThe term phreatic the word originates from the Greek phrear phreat meaning well or spring is used in hydrology and the earth sciences to refer to matters relating to ground water an aquifer below the water table The term phreatic surface indicates the location where the pore water pressure is under atmospheric conditions i e the pressure head is zero This surface normally coincides with the water table The slope of the phreatic surface is assumed to indicate the direction of ground water movement in an unconfined aquifer The phreatic zone below the phreatic surface where rock and soil is saturated with water is the counterpart of the vadose zone or unsaturated zone above Unconfined aquifers are also referred to as phreatic aquifers because their upper boundary is provided by the phreatic surface Speleology editIn speleogenesis a division of speleology phreatic action forms cave passages by dissolving the limestone in all directions 1 as opposed to vadose action whereby a stream running in a cave passage erodes a trench in the floor 2 It occurs when the passage is full of water and therefore normally only when it is below the water table and only if the water is not saturated with calcium carbonate or calcium magnesium carbonate A cave passage formed in this way is characteristically circular or oval in cross section as limestone is dissolved on all surfaces 3 Many cave passages are formed by a combination of phreatic followed by vadose action Such passages form a keyhole cross section a round shaped section at the top and a rectangular trench at the bottom Volcanology editMain article Phreatic eruption A phreatic eruption or steam blast eruption occurs when magma heats ground or surface water Biology editAnimals living within the phreatic zone of groundwater aquifers can be referred to as phreatobites 4 They are usually isopod or amphipod crustaceans such as species of Stygobromus though there is also a genus of snails Phreatodrobia and Phreatobius are a genus of catfish living within flooded leaf litter Alternative descriptions for such animals include stygobite 5 troglobite or Interstitial animals as they live in water between the particles of the flooded substrate They usually exhibit troglomorphism with a loss of colour and eyesight like the familiar blind cavefish which may also be referred to as phreatic fish Such animals can often be found in wells where human pursuit of water has dug down into their habitat See also editPhreatic zone Zone in an aquifer below the water table Vadose zone Unsaturated aquifer above the water table Water content Quantity of water contained in a material Category Aquifer articlesReferences edit New Mexico Bureau of Mines amp Mining Bulletin 117 Part I Discussion of Deposits and Events Glossary of Cave Related Terms Upper Cumberland Grotto Home Cave Retrieved 13 November 2010 John A Webb amp Stanley Lithco September 2001 Use of water chemistry to identify flow conduits in the porous Gambier Limestone southeast Australia PDF 7th Conference on Limestone Hydrology and Fissured Media France Universite de Franche Comte Sciences amp Techniques de l Environnement pp 333 336 ISBN 2 905226 14 5 Retrieved 13 November 2010 Passages are usually narrow vertical fissures but phreatic tubes circular or oval in cross section are present in some caves permanent dead link Glossary Phreatobite Speleogenesis UIS Commission on Karst Hydrogeology and Speleogenesis Glossary Stygobite Speleogenesis UIS Commission on Karst Hydrogeology and Speleogenesis External links edit nbsp Wikimedia Commons has media related to Underground water nbsp This hydrology article is a stub You can help Wikipedia by expanding it vte Retrieved from https en wikipedia org w index php title Phreatic amp oldid 1166818070, wikipedia, wiki, book, books, library,
