What Is A Black Smoker?

In 1949, research workers in the Red Sea found 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 many ways to the geysers that are found, say, in Yellowstone National Park and other places where there is volcanic activity. Since then, hydrothermal vents have been widely charted in mid-oceanic regions.

In the oceans, these vents typically form along mid-ocean ridges such as the East Pacific Rise. They are also found in the Red Sea where the Asian and African plates are drifting apart. At these junctions two or three tectonic plates (large sections of the earth's crust) are moving apart and new, young crust is being pushed up from the core.

The hot water flowing out from seafloor hydrothermal vents consists of sea water drawn into the system close to the volcanic structure by way of faults and porous sediments, plus some fresh water released by the upwelling magma from the earth's core. In terrestrial hydrothermal systems most of the water circulated within the fumarole and geyser systems is mainly ground water that has seeped down into the thermal system from the surface, but it also commonly contains some water originating from other sources. The proportions vary from place to place.

Water in the deep ocean usually has a temperature of approximately 3.5°C, but water emerges from these vents at temperatures ranging from 60°C up to as high as 400°C. Due to the high high water pressure at these depths (which could crush a submarine), water may become a supercritical fluid at these temperatures.

At a depth of 3,000 meters, the water pressure is over two hundred atmospheres (as salt water is more dense than fresh water). However the increase in 'saltiness' at this depth pushes the water close to its critical point. Therefore, water emerging from the hottest parts of some hydrothermal vents may be a supercritical fluid, having physical characteristics between those of gases and those of liquids.

Besides being superheated, the water may be extremely acidic, sometimes having a pH value as low as 2.8 - like vinegar, in other words. These subsea fumaroles are also known as smokers (or chimneys) and come in two distinct colours - black or white. The colour is a result of the particular chemical contents of the outflows. White smokers usually 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. Three hundred new marine species have been discovered, with a new food chain founded on chemosynthetic archaea at the base, supporting a wide range of life, including shrimp, clams, limpets and giant tube worms.

In 1991, it was shown that microscopic organisms known as Extremophiles were able to extract metals from seawater. Some observers suggest that some sulphur-oxidizing bacteria of the genera Beggiatoa, Thiothrix or Thiovulum play an active role in this precipitation of metals. It has been suggested that manganese nodules were formed in this way. In some areas of the ocean floor, there are significant fields of these manganese nodules.

Mining of manganese nodules was the cover story for the elaborate 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 this secret project by Howard Hughes. The enterprise was known as 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.


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