Hydrothermal Vents

Hydrothermal Vents

In 1977, Robert Ballard and J.F. Grassle of the Woods Hole Oceanographic Instution, were diving in Alvin near the Galapagos Islands when they discovered rocky chimneys up to 20 meters high. These chimneys were emitting dark, mineral-laden water that reached temperatures of 350 degrees Celsius. The occupants of Alvin had discovered the first documented hydrothermal vent.

These vents are formally defined as "springs of hot, mineral- and gas-rich seawater found on some oceanic ridges in zones of active seafloor spreading" (Garrison, 2004). Hydrothermal vents are found in ocean basins throughout the world. They are often compared to geysers of the deep ocean. And similar to above-ground geysers, hydrothermal vents play an important role in the formation and maintenance of this planet and the life that it supports. Therefore, hydrothermal vents play an integral role in our understanding of the planet and its origins and must be studied further. This area of research is important on a national and international level and can even have an impact on the state or local level as well.

Hydrothermal vents have been found everywhere from the Mid-Atlantic Ridge east of Florida, in the Sea of Cortez near Baja California, to even the Lake Baikal in southern Siberia. Scientists believe that vents are most common on oceanic ridges and are a result of rapid seafloor spreading. Oceanic ridges are found in locations in the ocean where divergent plate boundaries are prevalent. Due to the diverging plates, a fissure is created between these plates. This fissure provides a gap that dips down into the earth's asthenosphere. This gap is then filled with molten rock called magma that rises through crustal fractures. This magma is solidified as it enters the crustal fractures or erupts from volcanoes. This creates new ocean crust and is the basis for seafloor spreading. These crustal fractures also provide an opportunity for sea water to seep through these cracks. Once that seawater flows down into the lithosphere, it descends toward the hot magma chamber that is pushing through the spreading center. That water picks up minerals and metals off the surrounding rocks as it travels toward the magma chamber. As the mineral-laden water approaches the magma chamber, it is heated and therefore ascends through the spreading center and is "blasted" through fissures in the crust. These fissures that spew the heated, mineral-laden water are called hydrothermal vents. The heated water can reach temperatures of 400 degrees Celsius. Yet this water does not boil because it is under so much pressure from the tremendous weight of the ocean above. When the pressure on a liquid is increased, its boiling point goes up (http://www.ocean.udel.edu/deepsea/level-2/geology/vents.html).

Chimneys are often present atop many hydrothermal vents. These chimneys are smokestacks that form from the minerals and metals that the heated water is carrying. As the heated water is blasted up through the vent, it meets the near freezing water that resides at the bottom of the ocean. The mineral and metal particles break free from the heated water and fall around the fissure. Eventually, this process can build chimneys that are as high as seventy meters tall. However, these chimneys will not last forever. Eventually, they become too tall and the pressure and movement of the surrounding ocean topples the chimneys only to be rebuilt as the vent continues to operate. Depending on the type of minerals that the heated water carries through the hydrothermal vent, they are sometimes referred to as white or black "smokers". "Black smokers" are the hottest of the vents and spew mostly iron and sulfide, which combine to form iron monosulfide. It's this compound that gives the hydrothermal vent its black color. On the other hand, "white smokers" release water that is cooler than that of their "black smoker" counterparts. "White smokers" oftentimes spew compounds such as barium, calcium, and silicon. All of the compounds are white, therefore providing its vent with the nickname "white smoker".

Hydrothermal vents are also an important topic to study due to the life form that they support. Vents provide an environment for many different life forms. The hydrogen sulfide, carbon dioxide, and oxygen that are present at hydrothermal vents provide the ability of specialized bacteria to live. These bacteria are the base of the food chain from which other organisms in the hydrothermal vent community depend. For example, there are large crabs, clams, sea anemones, shrimp, and unusual worms that populate the hydrothermal vent community. These larger life forms rely on the native bacteria as well as chemosynthesis