Mohamed Omar
14-06-2009, 11:00 PM
A hydrothermal vent is a fissure in a planet's surface from which geothermally heated water issues. Hydrothermal vents are commonly found near volcanically active places, areas where tectonic plates are moving apart, ocean basins, and hotspots.
Hydrothermal vents are locally very common because the earth is both geologically active and has large amounts of water on its surface and within its crust. Common land types include hot springs, fumaroles and geysers. The most famous hydrothermal vent system on land is probably within Yellowstone National Park in the United States. Under the sea, hydrothermal vents may form features called black smokers.
Relative to the majority of the deep sea, the areas around submarine hydrothermal vents are biologically more productive, often hosting complex communities fueled by the chemicals dissolved in the vent fluids. Chemosynthetic archaea form the base of the food chain, supporting diverse organisms, including giant tube worms, clams, and shrimp.
Active hydrothermal vents are believed to exist on Jupiter's moon Europa, and ancient hydrothermal vents have been speculated to exist on Mars
http://f.zira3a.net/my-files/16366_11245009305.jpg (http://f.zira3a.net)
This is the black smoker type of hydrothermal vents
Physical properties
Hydrothermal vents in the deep ocean typically form along the Mid-ocean ridges, such as the East Pacific Rise and the Mid-Atlantic Ridge. These are locations where two tectonic plates are diverging and new crust is being formed.
The water that issues from seafloor hydrothermal vents consists mostly of sea water drawn into the hydrothermal system close to the volcanic edifice through faults and porous sediments or volcanic strata, plus some magmatic water released by the upwelling magma.
In terrestrial hydrothermal systems the majority of water circulated within the fumarole and geyser systems is meteoric water plus ground water that has percolated down into the thermal system from the surface, but it also commonly contains some portion of metamorphic waters, sedimentary formational brines and magmatic water that is released by the magma. The proportion varies from location to location.
The water emerges from a hydrothermal vent at temperatures ranging up to 400°C, compared to a typical 2°C for the surrounding deep ocean water. The high pressure at these depths significantly expands the thermal range at which water remains liquid, and so the water doesn't boil. Water at a depth of 3,000 m and a temperature of 407°C becomes supercritical.[4] However the increase in salinity pushes the water closer to its critical point.
Some hydrothermal vents form roughly cylindrical chimney structures. These form from minerals that are dissolved in the vent fluid. When the super-heated water contacts the near-freezing sea water, the minerals precipitate out to form particles which add to the height of the stacks. Some of these chimney structures can reach heights of 60 m.[5] An example of such a towering vent is "Godzilla", a structure in the Pacific Ocean near Oregon that rose to 40 m before it fell over.
The initial stages of a vent chimney begin with the deposition of the mineral anhydrite. Sulfides of copper, iron and zinc then precipitate in the chimney gaps, making it less porous over the course of time. Vent growths on the order of 30 cm per day have been recorded.[6]
Chimney structures that emit a cloud of black material are called "black smokers", named for the dark hue of the particles they emit. The black smokers typically emit particles with high levels of sulfur-bearing minerals, or sulfides. "White smokers" refer to vents that emit lighter-hued minerals, such as those containing barium, calcium, and silicon. These vents also tend to have lower temperature plumes.
An April 2007 exploration of the deep-sea vents off the coast of Fiji found those vents to be a significant source of dissolved iron
http://f.zira3a.net/my-files/16366_11245009445.jpg (http://f.zira3a.net)
This is the white smoker type of the hydrothermal vents
Hydrothermal vents are locally very common because the earth is both geologically active and has large amounts of water on its surface and within its crust. Common land types include hot springs, fumaroles and geysers. The most famous hydrothermal vent system on land is probably within Yellowstone National Park in the United States. Under the sea, hydrothermal vents may form features called black smokers.
Relative to the majority of the deep sea, the areas around submarine hydrothermal vents are biologically more productive, often hosting complex communities fueled by the chemicals dissolved in the vent fluids. Chemosynthetic archaea form the base of the food chain, supporting diverse organisms, including giant tube worms, clams, and shrimp.
Active hydrothermal vents are believed to exist on Jupiter's moon Europa, and ancient hydrothermal vents have been speculated to exist on Mars
http://f.zira3a.net/my-files/16366_11245009305.jpg (http://f.zira3a.net)
This is the black smoker type of hydrothermal vents
Physical properties
Hydrothermal vents in the deep ocean typically form along the Mid-ocean ridges, such as the East Pacific Rise and the Mid-Atlantic Ridge. These are locations where two tectonic plates are diverging and new crust is being formed.
The water that issues from seafloor hydrothermal vents consists mostly of sea water drawn into the hydrothermal system close to the volcanic edifice through faults and porous sediments or volcanic strata, plus some magmatic water released by the upwelling magma.
In terrestrial hydrothermal systems the majority of water circulated within the fumarole and geyser systems is meteoric water plus ground water that has percolated down into the thermal system from the surface, but it also commonly contains some portion of metamorphic waters, sedimentary formational brines and magmatic water that is released by the magma. The proportion varies from location to location.
The water emerges from a hydrothermal vent at temperatures ranging up to 400°C, compared to a typical 2°C for the surrounding deep ocean water. The high pressure at these depths significantly expands the thermal range at which water remains liquid, and so the water doesn't boil. Water at a depth of 3,000 m and a temperature of 407°C becomes supercritical.[4] However the increase in salinity pushes the water closer to its critical point.
Some hydrothermal vents form roughly cylindrical chimney structures. These form from minerals that are dissolved in the vent fluid. When the super-heated water contacts the near-freezing sea water, the minerals precipitate out to form particles which add to the height of the stacks. Some of these chimney structures can reach heights of 60 m.[5] An example of such a towering vent is "Godzilla", a structure in the Pacific Ocean near Oregon that rose to 40 m before it fell over.
The initial stages of a vent chimney begin with the deposition of the mineral anhydrite. Sulfides of copper, iron and zinc then precipitate in the chimney gaps, making it less porous over the course of time. Vent growths on the order of 30 cm per day have been recorded.[6]
Chimney structures that emit a cloud of black material are called "black smokers", named for the dark hue of the particles they emit. The black smokers typically emit particles with high levels of sulfur-bearing minerals, or sulfides. "White smokers" refer to vents that emit lighter-hued minerals, such as those containing barium, calcium, and silicon. These vents also tend to have lower temperature plumes.
An April 2007 exploration of the deep-sea vents off the coast of Fiji found those vents to be a significant source of dissolved iron
http://f.zira3a.net/my-files/16366_11245009445.jpg (http://f.zira3a.net)
This is the white smoker type of the hydrothermal vents