Sunday, August 19, 2012

There was once ice here

I had the good fortune of changing venue last week and do some hiking in my old graduate research area in Rocky Mountain National Park. Most of my work was done in the library but here on the eastern side of the Colorado Rockies we had the chance to look at some of the evidence left by glaciers. 

In this image you can easily see  the snow field up high, the remnants of the glacier that once filled this valley. I never made it up to the snow in this valley. In other nearby places we were able to see what little blue ice that was left. 

Below the snow lies the terminal moraine of the most recent advance, a small push that we dated about 1850 ish. That date always amazed me because of the advance of white guys and their families across the North American continent while the climate could support a glacial advance albeit a small one.   

Below the highest moraine is a solid rock outcrop that has been shaped by the passage of ice. This roche moutonnee shows ice movement from above downward. The upstream side is smoothed by the ice while the down stream side shows evidence of ice plucking. The ice partially melts by pressure, fills in the cracks and then refreezes with rock chunks stuck to the ice. The rocks move down stream leaving this choppy steep hillside behind.  

Below the image although unseen here is a great U-shaped valley. It doesn't get any more classical-glacial-terrain than here.

To study for my comps, I climbed into a number of these high valleys and physically touched all that the ice had left behind. Not only was it a fun way to study but it must have worked!