Teän (/ˈtiː.ən/ TEE-ən; sometimes written Tean without the diaeresis) is an uninhabited island to the north of the Isles of Scilly archipelago between Tresco, 1.5 kilometres (0.9 mi) to the west and St Martin's 300 metres (330 yd) to the east. Approximately 16 hectares (40 acres) in area the island consists of a series of granite tors with the highest point, Great Hill, rising to 40 metres (130 ft) at its eastern end. The low-lying land is overlain with glacial till and outwash gravels with glacial erratics abundant on the north coast beaches which indicates the southern limit of outwash from an ice sheet for which it is designated a Geological Conservation Review site.