AP Physics
Period: 7
6 June 2011
Life in Extreme Environments
Life in Extreme Environments details mid ocean ridges, hydrothermal vent circulation, life forms at hydrothermal vents and chemosynthesis versus photosynthesis. By using the GeoMapApp, we were able to investigate the Galapagos and the East Pacific Rise. We were able to see how life is able to survive in such a challenging environment.
Hydrothermal vents occur due to volcanic activity, water and fissures in rocks surrounding water. Fissures occur due to tectonic activity, such as seafloor spreading, which was further investigated using GeoMapApp. The heat source for the vents is magma and the vents are similar to geysers on land. The water emitted is hotter than the boiling point of water especially due to the enormous pressure put on the water by the ocean or the rock around, making it about 400 degrees Celsius. The vents can be found at any depth, with the shallowest at 30 meters deep near coastlines, and 3600 meters for the deepest. Using GeoMapApp we looked at bathymetry data from the East Pacific Rise. Most all of the vents were close to the coastline. The original discovery sight of vents was near the Galapagos Islands. Vents are located in tectonically active areas, and the East Pacific Rise is a fast spreading ridge where oceanic plates move at a rate of ten centimeters per year. We also saw that numerous hydrothermal vent fields were close to land that responded to earthquakes. The locations were surveyed between 2005 and 2007 and are more than 2500 meters below the ocean’s surface.
We then made graphs of elevation versus distance by taking cross sections of the ridge. The height of the ridges was nearly a mile high and the width is several hundred kilometers across. One famous edifice is named Godzilla and is 45 meters high. The color scale for topography is ranging from blue for deep to white for shallow. Hydrothermal vents were found at the top of the topographic feature. We then looked at another program that showed a high resolution and more precise image of the area. There was a long narrow depression, an axial trough, along the crest of the spreading center where the vents were concentrated, and it appeared to be about 50 meters across for much of the length and 10 meters deep. We learned that a fast spreading ridge has an axial trough going straight down the middle, with fault scarps separated by 6 kilometers. In a slow spreading, there are no axial troughs; instead they have rift valley floors separated by 10 to 20 kilometers. The East Pacific Rise is fast spreading, while the Mid Atlantic is slow spreading.
The ecosystem around the vents is based on chemosynthesis, a process similar to photosynthesis. Chemosynthesis is based on chemicals emitted and transported by the vents. These minerals include zinc, copper, magnesium, oxygen and the most important that makes chemosynthesis possible being hydrogen sulfide. The minerals emitted are toxic in low doses, so only certain life forms can live there. Food webs underwater function via chemosynthesis instead of photosynthesis, especially due to the absence of light. The website divediscover.com detailed the process. Cold seawater, about 2 degrees Celsius, seeps down into the ocean crust heated by magma to about 350 to 400 degrees Celsius and undergoes chemical reactions with rocks in ocean crust where the oxygen is removed and it becomes acidic, picking up dissolved minerals and hydrogen sulfide. Since hot liquids are less dense and more buoyant than cold, the hot hydrothermal fluids rise up through the crust, carrying dissolved metals and hydrogen sulfide. The hydrothermal fluids exit the chimney and mix with cold seawater. The metals carried combine with sulfur to form black minerals, giving the appearance of smoke. There are black smoking vents and white smokers. Oxygen and cold temperature trigger more reactions. This website also showed diffuse flow and chimneys. The life forms of the vents depend on this process for survival.
Life in the vent community was a surprise discovery in 1979. Due to the toxic chemicals and lack of light, only certain organisms can survive. Another difficult aspect is that vents can suddenly appear and disappear. Some life forms that live in the vent community are tubeworms, mussels, crabs, fish, octopi, worms, shrimp, dandelion, microbes, zoarcid fish and clams. These are not ordinary fish or crabs, most species in and around the vents are unique and not found anywhere else because they have to adapt to the uncertain conditions. Tubeworms have a shell made of chitin, which protects them from harsh chemicals and predators. There is a great chance for scientists to find new life and species in and around vents. Chemosynthetic bacteria provide nourishment, and can be found inside tubeworms and clams. Organic material floats into cooler water to be food for deposit feeding organisms. By using the cycle of chemosynthesis, some life can survive.
Hydrothermal vents connect to some topics covered in physics. Buoyancy played a factor in the rising of hot liquids during the process of chemosynthesis. Another topic discussed this year was pressure, which is the reason the vents are able to function. We did problems including geysers, and vents are underwater geysers. Using the concepts learned in physics, we were better able to understand how these vent communities function, the aspects of the ridges and why special life forms have the ability to survive in extreme environments.