Ramsey Island is less than 3.2 kilometres (2 mi) long and its highest point is 136 metres (446 ft) above sea level at Carnllundain, and is listed as a HuMP.

The island has a diverse geology for a relatively small area; it comprises sedimentary, volcanic and intrusive igneous rocks dating from the early Palaeozoic Era.

To the west of the Ramsey Fault which runs from Aber Mawr to Porth Lleuog, is Carnllundain which is formed from the tough rhyolitic tuffs of the Carn Llundain Formation.

Smaller areas of dark grey mudstones interbedded with debris flows grouped together as the Porth Llauog Formation occur around the margins of the rhyolite.

[3][4] Surveys in the 1990s and more recently discovered evidence of prehistoric cairns, field systems, barrows and other anomalies which suggest human activity on the island dates back up to 5,000 years.

[7] In the 13th century, the island was reported to be fertile, producing beef, sheep, goats, wheat, barley and oats.

The mill and kiln were in operation until the early 20th century, and in 1905 the island was sold into private hands and ceased being an ecclesiastical holding.

Other breeding species include ravens, common buzzards, peregrines, northern wheatears, gulls, auks, Manx shearwaters, razorbills and guillemots.