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Dive
Down to Deep Sea Hot Vents
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| Photo:
Dr. Verena Tunnicliffe |
Thousands
of metres below the surface of the ocean, super-heated, chemical-rich
water bursts out from under the sea floor.
Surrounded
by the virtual abyss of the deep ocean, these hot vents are an oasis
of life.
The
tectonic
plates that form the seabed are always moving.
When they shift away from each other, they form cracks in the ocean
floor. New oceanic crust flows out of the cracks from the Earth’s
interior. Ice-cold seawater seeps down in and is heated by molten
rock. The water then shoots up through the chimney structures, creating
a plume up to 300 metres high - or as tall as a 65-storey building.
When the super-heated water shoots out in the plume, it is accompanied
by dissolved minerals and metallic ions from below the ocean floor.
These minerals precipitate out when they come into contact with
the cold seawater and form the chimney structures of hot vents.
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Click
image to enlarge. Mid-ocean ridges – cracks in
the ocean floor – are found in every ocean around there
world. Therefore, hydrothermal sites are also found worldwide.
Credit: Tunnicliffe and Thomson, 1999 |
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Click
image to enlarge. Tectonic plates - here the the Pacific,
Juan de Fuca and North American Plates - are continously shifting.
When they move apart, hot magma seeps up through the cracks
and forms new oceanic crust.
Credit: University of Washington/Center for Environmental Visualization |
Most
of the deep ocean floor is almost barren. Hot vent areas, however,
are teeming with unique and diverse creatures, some of which are
found no where else on Earth. Hot vents, or hydrothermal vents,
are found in every ocean on the planet. Most are found at depths
of about 2225 meters (7,300 feet) deep, in areas where seafloor
spreading occurs and close to active underwater
volcanoes.
While
hot vents were only discovered in the last few decades, scientists
believe they may have existed for 3.5-4 billion years. Hot vents
are usually found thanks to a combination of scientific detective
work and a little good luck. A few clues can give away their hiding
places, such as an increase in water temperature, certain chemical
markers, megaplumes, and volcanic or tectonic activity. A good place
for researchers to look is also along the Mid-Ocean Ridge –
a broken chain of mountains and valleys that runs underneath the
oceans all the way around the world – where hot vents are
common.
Amazing
Life Forms
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| Tube
worms at the Endeavour Hydrothermal Vents.
Photo:
Dr. Verena Tunnicliffe |
Until
the late 1970s, it was believed that all life forms needed the sun's
energy to survive. Green plants change the sun’s energy into
food and are then consumed by other life forms. But when researchers
discovered hot vents in 1977, they found that some could get their
energy from chemicals.
Hydrogen
sulphide is released from the Earth’s interior in the plume
of heated water that shoots out through the hydrothermal vents.
Scientists found that bacteria could change this hydrogen sulfide
into food. Tube worms, clams, limpets, shrimp and other incredible
creatures found in vent areas feed on this bacteria. The biomass
- the number of life forms per cubic foot - and the diversity of
species in an established vent community could be as high as the
biomass and diversity of a rain forest.
New
Discoveries
Researchers
think that hot vents may play a role in controlling the temperature
and chemical composition of the oceans. Hot vents also provide an
outlet for the earth's inner heat. A new domain of life, Archaea,
was also added to the existing known domains, after researchers
discovered that organisms living in hot vents, as well as other
extreme environments, were different from anything else ever seen
before. Medical and industrial breakthroughs could be made as a
result of research at hot vent areas. Studying vent communities
might also help researchers understand the origin of life on Earth
and even give clues as to the possibility of life on other planets.
Sources:
Fisheries and Oceans Canada, University of Washington School of
Oceanography, University of California at Berkeley, ThinkQuest Ocean
AdVENTure
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