A circular hole formed in the rocky beds of rivers by the grinding action of stones or gravel whirled round by the water in what was at first a natural depression of the rock
A bowl-shaped depression in a rock surface that has been carved by the whirling action of stones in a stream bed
A smooth bowl carved into bedrock by the grinding action of stones whirling around an eddy in a river, such as at a rapids Many potholes were formed by torrents of glacial meltwater during the Ice Age The best place to see these along the Ice Age Trail is near the western terminus in Interstate Park formed when the St Croix River was much deeper than today