Monday, December 1, 2008

Pressure Ridges

Monday night I got to tour the pressure ridges located just beyond Scott Base. Tours of about 10 persons were taken by bus to Scott Base. We then walked up and down a defined flagged route through the pressure ridges. Click on the photo below to see a whole gallery of images taken last night.

The above photo is of me with Mt. Erebus, an active volcano, in the background.

A pressure ridge is formed when sea ice encounters the Ross Ice Shelf. The mostly immovable ice shelf acts as a backstop for the sea ice. The sea ice is compressed against the ice shelf through a variety of different forces including tidal action and the expansion of water as it freezes. The pressure upon the sea ice causes it to develop a variety of shape changes from gentle undulations to violent upheavals. These changes take place over years.

Many of the tall ice formations have veins of blue and grey running through them. The blue is from water's ability to filter out the red and infrared spectrum of light. This is said to be some of the purest ice on the planet. The pressure that forms these structures causes small bubbles of gas to become trapped within the ice. If some of this ice is chipped off and put into a glass of water, the melting ice will release these trapped pressurized gas bubbles with a cacophony of hissing, popping and spitting.

In the background of the last of these photos can be seen Scott Base, Castle Rock, and Mt. Erebus. You will notice the tiny plume of smoke trailing off to the right from the cone of Erebus, an active volcano.

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