Some of our happy group at Lighthouse Cave, San Salvador, Bahamas.
Thousands of visitors visit Old Faithful in Yellowstone National Park each year. The geyser shoots out a column of water several times a day. Features such as Old Faithful can also be found on the ocean floor. These geysers on the ocean floor are called hydrothermal vents. They constantly spew water into the ocean that is rich in minerals that help create habitats for organisms that cannot be seen in other areas of the world. The vents were first discovered in 1977 by a three person submarine operated by Woods Hole Oceanographic Institute at a depth of around 8,000 feet in the Pacific Ocean.
Hydrothermal vents are found on tectonic plate boundaries, most commonly mid-ocean ridges. Mid-ocean ridges are areas were two tectonic plates are moving away from each other and new crust is being formed. Magma is exposed to the sea water and is cooled which created the new crust. They can also be found in Subduction zones and hot spots. A subduction zone occurs when two tectonic plates collide together and one plate falls beneath the other. The plate that subdues is heated up by the magma beneath it and creates volcanic activity. A hot spot is an area of the ocean that has volcanic activity but is not at a plate boundary. At a hot spot, a tectonic plate glides over an area that is extremely hot and creates a volcano. As the plate continues to pass over the hot spot it creates more volcanoes. The Hawaiian Islands is an example of a hot spot. Hydrothermal vents a present at depth of between 7,000-8,000 feet.
As the tectonic plate activities occurs water seeps into little cracks and crevices in the crust. As the water passes through the crust and is exposed to the magma is collects many different minerals and metals. The water is then heated by the magma that is present at the areas. Since warm water is less dense than cold water, the heated water, with its minerals and metals, is shot up out of an opening and into the sea water. The water leaving the vents can reach temperatures of up to 750 degrees F. Though this water does not boil due to the extreme pressure present at this depth. Since the water leaving the vents are much warmer than the ocean water, just above freezing, the water cools very quickly and the metals present in the water settle down around the opening of the vent. As time goes on these metal build up on top of each other and grow. There have been reports of hydrothermal vents being as large as a fifteen story building. If the vents crumple or collapse, they just start back up and rebuild.
There are two different types of hydrothermal vents; Black Smokers, and White Smokers. The black smoker is the hottest of all the hydrothermal vents. It spews out mainly sulfides and iron. When the warm water hits the cool water the minerals precipitate and it creates the black smoke effect. The white smoker typically has cooler water than that of the black smoker and is generally smaller in size as well. The minerals in the white do not contain metals which prevent it from having the black smoke effect. The structure in which the hot fluid flows out of is called a chimney. These chimneys can reach up top tens of meters tall. They are made of dissolved minerals and metals that are present in the water leaving the vents such as sulfur, copper, zinc, and iron. These structures will continue to grow as long as water containing the minerals flow out of it. Scientists have observed some chimneys that grow at around thirty centimeters a day. The chimney is very fragile and can collapse if it grows too high.
The ecosystem is which hydrothermal vents are present has such extreme conditions that it is a wonder there is life there at all. At depths of between 7,000 Š 8,000 feet below the surface of the water pressure can reach 300 atmospheres. The temperature of the water in these areas can range from 403 degrees Celsius where water leaves the vents to 2 degrees Celsius away from the vents. The water has extremely high levels of hydrogen sulfide which are toxic to toxic to most living organism. The water leaving the vents is also very acidic. The pH in hydrothermal vent communities can be as low as 2.8 which is unhealthy for most living organisms. The majority of living organisms need sunlight to live. Through photosynthesis plants transform sunlight into energy and use it as food. But at such great depths there is no sunlight available to the organisms in a vent community. They use a process called chemosynthesis. Chemosynthesis is the process of converting inorganic material into food using chemical energy. Bacteria that are present in a vent community go through chemosynthesis to create the base of the food web in the hydrothermal community.
With such extreme conditions it is a wonder as to how any life form can exist around hydrothermal vents. Hydrothermal vent community makes way for organisms that seem almost alien and cannot be seen anywhere else. Creatures such as crab, fish, tube worms, shrimp, and chemosynthetic bacteria have a way of surviving the extreme conditions. These creatures will feed off of the chemosynthetic bacteria or feed off of the creatures that eat the bacteria. Some of the creatures in the community such as the tube worm do not have a mouth or a digestive track or an anus. The bacteria will give the creature the necessary nutrients through its skin. Because of this, a food web is produced. At the base of the web there are the primary producers including chemoautotrophic sulfur bacteria. Then there are the secondary producers which feed off of the bacteria including, tube worms, clams, mussels, and shrimp. Finally in the web are the predators. These include fish and crabs and they feed off of the creatures that eat the bacteria. So either directly or indirectly each creature in a hydrothermal vent community depends on the bacteria. Some believe that life on the planet started in such a way as it does in a vent community. Conditions on Earth were much different and much harsher than what they are today. So it have been some special bacteria that started life and more and more creature began to evolve.
Processes within a vent community are strange. Some things like the chimneys and tube worms can grow at a very rapid pace. Chimneys can grow centimeters every day and tube worms have been known to grow several meters each year. But, while these may grow at a fast rate when the organisms die, decomposition work slower. On one expedition scientists observed several dead tube worms on the community floor. A year later when the scientists returned to the same site the dead tube worms were relatively unchanged. Scientists are not really sure why this is but they believe it is due to the extreme pressure and the lack of the typical decomposing organisms that are usually present on land and other areas of the sea. A hydrothermal vent communityÕs life is unpredictable. It may live for a few years or it may continue to live a long life. Volcanic activity, earthquakes, or the collapsing or a chimney may end the life of a vent community. If one of these events take place it can block the flow of the vent fluid and end the rare relationship between the surrounding and its inhabitants.
If it were not for the extreme depth of the locations of the hydrothermal vents mining these areas would be very profitable. Copper, magnesium, and even gold can sometimes be found in a vent community. But because it is so hard to reach it would cost more money to mine it than you would make if you did. This does not mean that these vent community cannot serve a purpose to use today. Some of the bacteria extracted from the vents are being used to help break down dangerous hydrogen sulfide waste create by some industries.
There is no doubt that hydrothermal vents are unique and important structures on this planet. In an area where no life should be present a vibrant community exists with creatures that cannot be seen anywhere else on Earth. These communities are so unique and so hard to explore that it wasnÕt discovered until 1977. This brings up the question of what else is out there. Some people may say that space is the final frontier and we need to explore it more, but I say why not explore our own planet more. With 71% of the EarthÕs surface underwater there has to be much much more that we do not even know about yet. The fact of the matter is hydrothermal vents are a huge step towards the exploration of the deep blue sea.
Garrison, Essentials of Oceanography, 3rd edition, Brooks/Cole
Office of Naval Research, http://www.onr.navy.mil/focus/ocean/habitats/vents1.htm
University of Washington School of Oceanography, http://www.ocean.washington.edu/people/grads/scottv/exploraquarium/vent/intro.htm
Voyage to the Deep, http://www.ocean.udel.edu/deepsea/level-2/geology/vents.html, 2000
Wikipedia the Free Encyclopedia, http://en.wikipedia.org/wiki/Hydrothermal_vent, 2006
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