Wednesday, August 30, 2006

Weird Stuff on Earth

A team of scientists based in Japan and Germany has found an unusual "lake" of liquid carbon dioxide beneath the ocean floor.

On Earth's surface carbon dioxide (CO2) is normally a gas, but in the cold, high-pressure ocean depths it cools and becomes a liquid.


Inagaki's team found the lake while studying hydrothermal vents—undersea volcanic hot spots—in the East China Sea off the coast of Taiwan.

The lake's presence was unexpected, because the seamount lies only 4,600 feet (1400 meters) below sea level. At that depth, liquid CO2 is lighter than water and will slowly rise, eventually bubbling into the air as gas.

Normally liquid CO2 has to be at a depth of 10,000 feet (3,000 meters) for it to be dense enough not to rise.

In this case, Inagaki's team says, CO2 has been moving upward from a deep magma chamber.

As it nears the seabed, the CO2 encounters cold water in the top layer of sediment. It reacts with this water to form a type of ice called a carbon dioxide hydrate.

The hydrate creates a cap in the sediment that traps additional liquid CO2 beneath it.

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