Glacial features at Hull

Below, you see a picture of Hull. Along the Northern part of the town, there are two drumlins. A drumlin is a hill composed of a pile of sand, rocks, gravel, boulders, etc. that have were left behind as glaciers retreated over 12,000 years ago. One interesting thing about this particular spot is that the drumlins are connected by sand. This connecting feature is known as a tombolo.

Usually drumlins have a very regular oval shape. If you click on the picture below, you can see a larger version of the tombolo. The elevation has been exaggerated to show the two drumlins. Notice in the larger version that one of these hills (on the left) seems to have been cut at a very steep angle. What are some different reasons why this may have happened?