Friday, December 19, 2008
Mt. Cardigan, NH, summit ledges polished and weathered with soil forming in fissures in the solid rock
There are several other puzzles to solve that aren’t so much about the glaciers but how long it took the glacier to melt and what happened immediately after the glacier ablated. That time period itself is worth thinking about. For instance, I like to try and picture what the mountains looked like the morning after the glacier left. Was the whole region swept clean, as in this series of photos of Mt. Cardigan, with the mountains polished to a high sheen like granite countertops or were they covered with debris made up of random sized rocks, sand and gravel? In the period of time since the glacier melted, roughly the last 11,000 to 12,000, years there has been some weathering. The same forces Andrew Reily discusses in his paper including temperature variations, wind, frost, and precipitation, over thousands of years would cause rocks and soils to weather. The question is how much has changed in those ten millennia? Geologically it isn’t a lot of time but a few of the things that would be effected would be soil development, types of vegetation, biota associated with soils and plant communities, the movement, or sheet flow, of water, containment of water, mass wasting in the form of landslides, all representing energy transfers and “movement” towards increased stability.