Notice the snow trapped in shadow. The photo was taken in September the snow fell the previous winter. During the ice ages more than ten thousand years ago much more snow fell and was trapped. It did not melt during the summer and accumulated to form three hundred meter thick glaciers. These glaciers flowed downhill plucking granite blocks from the surrounding mountains, deepening and steepening the walls of river valleys. Wolf's Head in the center of this photo is a thin blade of rock. It was plucked thin on both sides .

Notice the smooth surface of this granite rock. Look closely at the shadows and you will see that it is slightly grooved from the top left to the lower right. Two parallel shadows highlight chatter marks where ice froze to the surface of the rock and pulled it apart. The grooves and chatter marks show that ice flowed from left to right across this rock.

Notice this steep sided flat topped volcanis remnant in Iceland. It is a Moberg, a volcano that erupted through a glacial icecap.

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Scientific Explorations with Paul Doherty

© 2000

4 October 2000