tag:blogger.com,1999:blog-1228690739485734684.post8644232500896538328..comments2024-03-28T22:13:17.139+00:00Comments on Stonehenge and the Ice Age: Where was the Somerset GBG Limit?BRIAN JOHNhttp://www.blogger.com/profile/00413447032454568083noreply@blogger.comBlogger3125tag:blogger.com,1999:blog-1228690739485734684.post-66577849940532012892012-08-26T14:54:38.889+01:002012-08-26T14:54:38.889+01:00Yes -- it's been known for a long time that in...Yes -- it's been known for a long time that in some circumstances glacier ice can freeze onto the bed and effectively protect a pre-existing landscape. Normally this means relatively thin ice and a situation in which pressure melting cannot occur on the bed. There may be some movement higher up within the ice mass, by shearing and creep, but ice movement on the bed might be so slow as to be virtually unmeasurable. On the other hand, where we have thicker ice, as in valleys or depressions, pressure melting will be possible at sub-zero temperatures, and bingo -- there can be much more rapid ice movement and substantial erosion on the glacier bed. This is why you get ice streams within large ice sheets and ice caps, and why trough depths get exaggerated while the flanks of troughs may survive even if the rock there is rotten or fractured. It's all in "Glaciers and Landscape"!!BRIAN JOHNhttps://www.blogger.com/profile/00413447032454568083noreply@blogger.comtag:blogger.com,1999:blog-1228690739485734684.post-67097157567314039502012-08-26T12:53:49.017+01:002012-08-26T12:53:49.017+01:00"landscape protection" rather than alter..."landscape protection" rather than alteration. <br />What does that mean? No overall erosion/deposition?<br />M Myris of Alexandrianoreply@blogger.comtag:blogger.com,1999:blog-1228690739485734684.post-67331541577049988112012-08-26T12:37:30.955+01:002012-08-26T12:37:30.955+01:00I should explain that GBG means "Greatest Bri...I should explain that GBG means "Greatest British Glaciation"......BRIAN JOHNhttps://www.blogger.com/profile/00413447032454568083noreply@blogger.com