Water And Oceanography

What a Black Smoker is



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Black smokers are objects of intense interest to oceanographers, geologists and biologists. They are hydrothermal vents found near the oceanic ridges, which mark the constructive plate boundaries. Found only in the deep oceans, the first black smoker was discovered in 1977 on the East Pacific rise. Since then many others have been found in both the Atlantic and Pacific oceans.

Water enters the oceanic crust through cracks then circulates towards the magma chamber underneath the oceanic ridge where it heats up. As the water heats up it dissolves some of the minerals within the basaltic rocks of the oceanic crust. The hot water then rises through the crust to rejoin the ocean at the hydrothermal vents.

The hot hydrothermal water leaving the vent can reach a temperature of about 400 C°(760°F). Despite this high temperature, the water does not boil because of the intense pressures at that depth. The water contains many dissolved minerals, which, as the hot water from the vent mixes with the cold water of the ocean, precipitate out. Hydrothermal vent water is also extremely acidic with a pH as low as 2.8.

The precipitated minerals form vent chimneys from which the salt rich water gushes. A chimney recently recovered from a hydrothermal field in the Pacific by a submersible, consists of a mixture of pyrite and iron oxide. Vent chimneys grow very fast. Measurements made by geologists show that chimneys can grow 9 meters (30 feet) in eighteen months. They can also grow to quite a size; one named “Godzilla” reached a height equivalent to a 15-storey building before toppling over. The black “smoke” consists primarily of the compound iron monosulfide.

In such extreme conditions, the last thing scientists expected was a thriving community of animals. They were in for a surprise. Vent fields have a unique ecology based on chemoautotrophic bacteria. These bacteria use the heat from the hydrothermal water and the sulfide compounds to produce energy. With this energy, they can combine carbon dioxide and water to produce complex organic molecules. Just as plants and photosynthetic bacteria are the primary producers, where there is sunlight so the chemoautotrophic bacteria are the primary producers around the hydrothermal vents.

Since the discovery of these colonies of animals living in the depth of the oceans, over 300 species of animals have been identified. Some animals like the eyeless shrimps found near vents in the Atlantic shrimps graze on the mats of bacteria surrounding the vents. Others like the white crabs eat other animals.

In the Pacific, biologists found colonies of giant tubeworms (Riftia pachyptila). Growing to over 8 feet long they were an enigma. They do not have a mouth or gut and biologists were at a loss to explain how an animal could get so big if it did not eat. These creatures live with symbiotic bacteria within them. The bacteria provide the worms with all the nutrients they require while the worms provide the bacteria with a home. Young tubeworms do have a mouth, which allows access for the bacteria, as they grow they lose both their mouth and gut.

The low pH means that some snails have evolved without shells, as the calcium carbonate, normally forming the shells of gastropods, will dissolve at a low pH. Recently a gastropod was discovered near a vent that uses iron sulfides to form its shell.

The Pompeii worm (Alvinella pompejana) will survive in temperatures as high as 80°C (131°F). No other animal has been found that can survive such extreme heat.

Paleontological evidence shows that these strange communities in the ocean depths have existed for millions of years. They survived the great extinction that killed the dinosaurs as well as many other life forms. Some palaeontologists believe that the earliest life forms to evolve on earth are similar to the hydrothermal vent colonies we can see today.

Black smokers are objects of intense interest to oceanographers, geologists and biologists. They are hydrothermal vents found near the oceanic ridges that mark constructive plate boundaries. Found only in the deep oceans the first black smoker was discovered in 1977 on the East Pacific rise. Since then many others have been found in both the Atlantic and Pacific oceans.

Water enters the oceanic crust through cracks then circulates towards mama chamber underneath the oceanic ridge where it heats up. As the water heats up it dissolves some of the minerals within the basaltic rocks of the oceanic crust. The hot water then rises through the crust to rejoin the ocean at the hydrothermal vents.

The hot hydrothermal water leaving the vent can reach a temperature of about 400°C (760°F). Despite this high temperature, the water does not boil because of the intense pressures at that depth. The water contains many dissolved minerals, which, as the hot water from the vent mixes with the cold water of the ocean, precipitate out. Hydrothermal vent water is also extremely acidic with a pH as low as 2.8.

The precipitated minerals form vent chimneys from which the salt rich water gushes. A chimney recently recovered from a hydrothermal field in the Pacific by a submersible, consists of a mixture of pyrite and iron oxide. Vent chimneys grow very fast measurements made by geologists show they can grow 9 meters (30 feet) in eighteen months. They can also grow to quite a size; one named "Godzilla" reached a height equivalent to a 15-storey building before toppling over. The black "smoke" consists primarily of the compound iron monosulfide.

In such extreme conditions, the last thing scientists expected was a thriving community of animals. They were in for a surprise. Vent fields have a unique ecology based on chemoautotrophic bacteria. These bacteria use the heat from the hydrothermal water and the sulfide compounds to produce energy. With this energy, they can combine carbon dioxide and water to produce complex organic molecules. Just as plants and photosynthetic bacteria are the primary producers, where there is sunlight so the chemoautotrophic bacteria are the primary producers around the hydrothermal vents.

Since the colonies of animals living in the depth of the oceans were discovered, over 300 species of animals have been identified. Some animals like the eyeless shrimps found near vents in the Atlantic shrimps graze on the mats of bacteria surrounding the vents. Others like the white crabs eat other animals.

In the Pacific, biologists found colonies of giant tubeworms (Riftia pachyptila). Growing to over 8 feet long they were an enigma. They do not have a mouth or gut and biologists were at a loss to explain how an animal could get so big if it did not eat. These creatures live with symbiotic bacteria within them. The bacteria provide the worms with all the nutrients they require while the worms provide the bacteria with a home. Young tubeworms do have a mouth to allow access for the bacteria as they grow they lose the mouth and gut.

The low pH means that some snails have evolved without shells, as the calcium carbonate normally forming the shells of gastropods will dissolve at a low pH. Recently a gastropod was discovered near a vent that uses iron sulfides to form its shell.

The Pompeii worm (Alvinella pompejana) will survive in temperatures as high as 80°C (131°F). No other animal has been found that can survive such extreme heat.

Paleontological evidence shows that these strange communities in the ocean depths have existed for millions of years. They survived the great extinction that killed the dinosaurs as well as many other life forms. Some palaeontologists believe that the earliest life forms to evolve on earth are similar to the hydrothermal vent colonies we can see today.


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