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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.