Friday, December 19, 2008

Mt. Washington and Mt. Jefferson (right) from Mt. Adams, 2008

Andrew Reily’s paper on The Big Wind (above) got me thinking about the complex theories about glaciation in the White Mountains: ways glaciers, over millions of years, have impacted the present day natural history of the White Mountain. So I want to use this picture from Mt. Adams that I took a few weeks ago to begin an exploration of glaciers and the whole bit about glaciation. There are two major things I want you to imagine with me using this photo. One of them, perhaps the easier one, is to imagine you're standing on top of Mt. Adams and looking down into the Great Gulf, Jefferson's Ravine (partially hidden there on the right), and an unseen basin, or small glacial cirque hidden behind that ridge of Mt. Jeffersons in the photo's center. We refer to that as Jefferson's Knee. Now imagine it's 140,000 years ago. Now, Adams would probably be much higher, by a thousand feet or more, but let's say the scene is similar to the one in the photo. What you would see is a fairly large glacial system, an Alpine Glacier, like you would see on Mont Blanc, or Annapurna. It would fill the Gulf half way and have tributaries coming out of Jefferson Ravine and that nook below Sphinx Col. There would be a bergschrund and crevasses in the upper parts of the glacier, the "accumulation zone". There would be rocks and debris on top of the glacier from landslides coming off the side walls. So, yes, an extensive glacier that flows down and out to the valley below.

So that's one bit of imaging. The other is a bit more dramatic, I think. In the photo my eye level is about 5805 feet above sea level and we’re looking across the Great Gulf at Mt. Jefferson on the right and Mt. Washington straight ahead and due south. Mt. Washington is 6288 feet above sea level so it’s 483 higher than my present eye level. So, imagine that instead of standing on the highest rock on the summit of Adams gazing up at the summit of Mt. Washington we’re actually standing 800 feet above Mt. Adams and on an immense ice field extending to the horizon in every direction. No mountains are in view, just ice, snow and crevasses as far as the eye can see.
That would be 20,000 to 115,000 years ago when the last continental glacier, the Wisconsinan, was here in the Whites. (cont.)

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