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Do You Know Your Fumarole From Your Elbow?
In 1949, researchers in the Red Sea discovered hot, highly saline water in pools on the sea bottom. This hot sea water emanated from so-called hydrothermal vents. These hydrothermal vents are equivalent in ways to the geysers that are found, say, in Hawaii and other places where there is volcanic activity. Since then, hydrothermal vents have been widely found in the oceans.
In the oceans, hydrothermal vents are found along mid-ocean ridges such as the Mid Atlantic Ridge. The vents are also found in the Red Sea where the Asian and African plates are drifting apart. At these junctions two tectonic plates (large sections of the earth's crust) are diverging and new, young crust is being pushed up from the core.
The flowing out from seafloor hydrothermal vents consists mainly of sea water drawn into the hydrothermal system close to the volcanic structure via and porous sediments or volcanic strata, plus some fresh water released by the upwelling magma from the earth's core. In hydrothermal systems on land most of the water circulated within the fumarole and geyser systems is mostly ground water that has seeped down into the thermal system from the surface, but it also often contains quantities of water originating from other sources. The proportions vary from location to location.
Water in the deep ocean typically has a temperature of about 2-4°C, but water flows from these vents at temperatures ranging from 60°C up to more than 400°C. Due to the high huge water pressure at these depths (which could crush a submarine), water can become a supercritical fluid at these temperatures.
At a depth of 3,000 meters, the water pressure is over 200 atmospheres (as salt water is more dense than fresh water). However the increase in salinity at this depth pushes the water close to its critical point. So, water pouring out from the hottest parts of some hydrothermal vents can be a supercritical fluid, with physical characteristics between those of gases and those of liquids.
Besides being superheated, the water can be very acidic, sometimes having a pH value as low as 2.8 - like vinegar. The underwater fumaroles are also known as chimneys (or smokers) and come in two distinct types - black or white. The differing colours reflects the particular chemical contents of the outflows. White smokers tend to have a high carbon dioxide content. The outpouring is sulphur-rich and can contain large proportions of metals such as zinc, manganese and even gold. Over three hundred new marine species have been discovered, with a whole new food chain founded on chemosynthetic archaea at the base, supporting diverse life, including giant tube worms, clams, limpets and shrimp.
In 1991, it was shown that microscopic organisms known as Extremophiles were able to concentrate metals from seawater. It is believed that some sulphur-oxidizing bacteria of the genera Beggiatoa, Thiothrix or Thiovulum are active in in this precipitation of metals. It has been speculated that manganese nodules were formed in this way. These nodules are widespread in certain areas of the ocean floor.
Deep sea mining of manganese nodules served as a cover story for the incredible attempt by the CIA to covertly raise the sunken Soviet submarine K-129, using the Glomar Explorer. The Explorer was a ship built specifically for the task by Howard Hughes. This was called Project Jennifer, and failed to recover the submarine.
So, Black Smokers (or underwater fumaroles) have a lot to answer for, and extracting gold from sea water economically - well, that is only just around the corner.
About the Author
Gold in vast quantities from the sea? Find out how and where, and enjoy a fast paced story set in the very near future: the lure of gold in vast quantities, near collapse of the international monetary system and naval confrontation . Up to the minute and beyond - discover more now about the Gate of Tears
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