The Chasms are a network of deep, narrow clefts and sea caves cut into the cliffs of the south coast near Cregneash, formed as thick beds of quartz-arenite sandstone in the Mull Hill Formation fracture and slump toward the sea. The sandstone itself was laid down hundreds of millions of years ago by underwater turbidity currents carrying sand grains into deep water. The offshore sea stack known as the Sugarloaf Rock, visible from the clifftop path between Port St Mary and the Sound, has lent its name to a local café and is a favourite subject for coastal photographers.