|
An international team of scientists under the lead of Andrea Koschinsky-Fritsche, Jacobs Professor of Geoscience, registered the record water temperature 464 °C at a hydrothermal vent located in 3000 m water depth at 5 °S at the Mid-Atlantic Ridge. The measurement, taken on the 68th cruise of the German research vessel METEOR, now has been published in the current issue of the Geology (DOI: 10.1130/G24726A.1).
[
Aug
08, 2008]
At 3000 m depth 407 °C marks the critical temperature, where water is no longer a normal fluid but reaches a so-called "supercritical" state, somewhere between fluid and vapor. Compared to water, this fluid is denser than vapour, but it is lighter than liquid water. "It' IS water," says Andrea Koschinsky-Fritsche, "but not as we know it." This special state of aggregation for instance differs markedly from liquid water in the way it leaches materials such as metals from the surrounding bedrock. This process results in super-hot solutions of highly unusual composition, the cruise leader adds.
Gold, copper, iron, manganese, sulphur and many more are brought out of the Earth's interior when the water is ejected from the hydrothermal vents, also called “black smokers” because of their characteristic particle plume in the discharge water. Some, such as sulphur and manganese, provide energy to the locally adapted organisms, which have no light to power a food chain. Iron is essential for the growth of all phytoplankton. Koschinsky-Fritsche estimates up to half the manganese and one tenth of the iron found in the oceans could come from vents. But because supercritical fluids have never been observed in nature, little is really known about how this happens.
The water temperature of 464 °C now published has never before been seen in nature. It was measured during a 20 s interval at one site of the hydrothermal vent system, which is characterized by multiple fluid emanations at variable temperatures. The scientists used a special temperature sensor operated by a deep-sea robot t in 3000 m water depth. Moreover, the boiling fluids of the vents at 5 °S at the Mid-Atlantic Ridge, where the African and the South American continental plates drift apart 4 cm per year, causing increased volcanic activity, were filmed. Normally the temperature of the circulating seawater cooling the volcanoes emerging in this area does not exceed a maximum of about 350 °C when welling out of the sea floor.
"We stand to greatly improve our models of fluid circulation and heat and mass transfer," says Margaret Tivey, a geochemist at the Woods Hole Oceanographic Institute (WHOI) in Massachusetts. Because of the extreme conditions, computer models are the only way of understanding the processes that drag elements out of the seafloor at hot vents. "It's not yet possible to drill into active vents," explains Koschinsky-Fritsche. "Temperatures are so high, much of drilling equipment would melt and joins would not work anymore." The data from the new vents will be invaluable in testing the models.
 |
 |
 |
Meteor Expedition M68/1 |
|
|
|
|
The Meteor expedition M68/1 took place from April 27 to June 2, 2006, in order to explore the correlation between volcanism, water circulation inside and above the sea floor and hydrothermal vent organism communities. In addition to the super-hot vent it also discovered other, to date uncharted hot deep-sea wells. This was facilitated by combining the abilities of the autonomous deep-sea vehicle „ABE“developed by Woods Hole Oceanographic Institute and the remotely operated vehicle „QUEST 5“ developed by the University of Bremen.
|
|
|
