The steepest slopes are found on the northwest side of the East Bay Hills, where soft Windsor Group rocks form a narrow band along the shore. The valley of Breac Brook, at the north end of East Bay Hills, appears to be an ancient coastal valley which was filled by Windsor Group deposits and is now being exhumed. The fault line on the southeastern margin can be seen in some areas (e.g., northeast of Oban) but in general does not form a prominent scarp slope.