 Superficial deposits consist largely of modern day beach deposits, some raised marine deposits and blown sand.There are also areas of glacial till of Pleistocene age and of peat formed in the postglacial period.Although Colonsay appears bare and somewhat forbidding on approach from the sea, its landscape is varied, with several beautiful sandy beaches, and a sheltered and fertile interior, unusually well-wooded for a Hebridean island.