Part 2: Journey to the surface
When the oil and gas reaches the sediments nearest to the
seafloor, it tends to spread out from the confines of the faults and seep
through the looser sediments. The entire area around a fault is transformed
by the seepage--producing many unusual biological and geological effects.
For the moment though, let's follow the oil and gas that
escapes into the water. |
The seafloor areas affected by seepage are often 100 to
500 meters across, but within this distance there are generally no more
than four or five localized vents that are actively releasing oil droplets
and gas bubbles.
The gas is more buoyant than the oil, but the entire plume
of droplets and bubbles tends to rise in a tight column, bending to and
fro as it is pushed by internal currents until it reaches the surface.
The gas bubbles expand as they rise and separate into smaller
bubbles. By the time the gas reaches the surface, much has dissolved into
the water.
The oil drops expand relatively little during their trip
to the surface. Once the hit the surface, the drops burst into a circle
of rainbow sheen. |
A drop of oil from a seep in the Gulf of Mexico bursts on the surface
after rising up through 560 meters of water.
 Where is the oil layer around
the drop thickest? How do you know?
What is the volume of gas in a bubble 1 centimeter in diameter at a depth
of 500 meters? What would the total volume of this gas if it all reached
the surface?
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