The ridge that extends southwestward from the crater is judged to represent a till ridge or bedrock fluting (Crag-and-tail feature). Crag-and-tail features are a common occurrence in some drumlin fields. It likely formed below the southwestward flowing Laurentide Ice Sheet during the last glaciation. Other streamlined erosional features, e.g. oriented bedrock ridges and troughs, Flat-topped ridges, and bedrock lineations indicate that the bottom of this part of Lake Ontario, including Charity Shoal, have been significantly modified by glacial erosion.