This photo, taken in Glacier Park, shows scratches on bedrock that were made as a valley (a.k.a. alpine) glacier moved across here. Large rock fragments stuck to the bottom of the ice caused the gouges, which are called “glacial striations.”
How to “track” a glacier . . .
How far south? . . .
Below: The glacier that formed the Polson moraine did not cause the polished gouge in this outcrop several miles south of Polson. It was caused by a large rock stuck to the underside of glacier that flowed across this area during an earlier ice age about 70, 000 years ago. The yellow arrow marks the striation and shows flow direction.
Photo by Bruce Baty
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Earth Science Teacher at Helena High School