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GeogOnline - Glacial Erosion Landforms 3
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Beehive Mountain a roche moutonnee from the Acadia National Park in the state of Maine, N.E. USA. The glacier (in the past) smoothed the upstream side of the rock protuberance by abrasion but the steep south facing side was affected by plucking. One theory says that the ice was under pressure on the upslope side and some pressure melting may have occurred. On the downstream side this meltwater would enter joints in the rock. With the removal of pressure the water would freeze. as the ice glacier continued to slide the rocks would be ripped away (plucking).
When a glacier moves across the underlying rock, the process of abrasion wears it away. It is the fragments of rock held in the ice that do the abrading, scraping across the rock surface like nails across a wooden desk top. Larger rock fragments leave deep scratch marks behind them. These scratch marks are straight parallel lines that reveal the direction of ice movement.

Freshly exposed striations have a preferred orientation of rock grains. By lightly running a finger along the striation it is possible to discover that when moving one way along it, the rock feels smooth, but when moving the other way it feels more coarse. The moving ice leaves the rock grains aligned with the direction of movement, so when the striation feels smooth, your finger is moving in the direction of ice flow. When the striation feels rough, you are moving against the ice flow. This test doesn't always work, and wont work on striations that have been exposed for a long period of time. In the picture above, Christopher is establishing the direction of ice movement by running his fingers over the striations. He decided that the ice had been moving from his right to his left, which was just as well since the glacier was still flowing in that direction the valley just below him!
Knock and lochan scenery - Scottish Highlands.These show one influence of geology in the erosion of a glacial upland. Geologically resistant rocks form features like roche moutonnee which make the hillocks (knocks). Weaker rocks are overdeepened and become waterfilled areas after the ice retreats. The hollows are the lochans.