Saturday, November 12, 2011

What's a Pressure Ridge?

Shockingly there isn't much shopping down here.  That's a good thing.  However, there still are a couple places on the continent albeit limited.  Nearby is one of the locations outside of town here at Mcmurdo.  Our Kiwi neighbors at Scott Base are a short 3 mile hike away so up and down an icy hill we went in search of Christmas presents and a diet coke. 

Fortunately we walked because we didn't have any New Zealand dimes.
As you approach Scott Base one of the most amazing features right at their location is the sea ice / shelf ice confluence.  Where the two meet is a dramatic scene of the forces of Mother Nature at work with the formation of mangled ice and pressure ridges for miles. So just what is a pressure ridge?
Scott Base and the pressure ridges from a shot I took last season flying.  Mt Erebus in the background.
It's an ice formation typically found on large expanses of sea ice during the winter. In the most basic sense, a pressure ridge is a long crack in the ice that occurs because of repeated heating and cooling on the surface of the ice in addition to the tidal forces and flow of the ice shelf towards the sea.
Mangled Ice

Looking Back at Erebus

A handful of Weddell seals coming up for some sun through breathing holes created by the ridges
In cases of extreme cold, ice will shrink in volume like any other solid, opening up cracks in the surface that are completely frozen over. The cracks quickly fill with water and freeze again, but when the temperature rises later, the ice expands and forces itself upward along the lines of the crack, in much the same fashion that plate tectonics creates mountain ranges, albeit on a much smaller scale. 

That's today's lesson folks.  It was a success in it was a great 5-6 mile hike, I found a diet coke, got a great little Christmas ornament and saw some beautiful and twisted ice.  

Happy Veteran's Day to all my fellow brethren past and present.  Thank you for yours and your family's sacrifices.  Now back to my Saturday.  Cheers!

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