[4][5] An Tiaracht is about a kilometre from east to west, and 500 metres (1,600 feet) from north to south.

[6] Like the other Blasket Islands, Tiaracht holds large numbers of seabirds, with internationally important populations of Manx shearwater and European storm-petrel.

The number of auks, especially puffins, has apparently fluctuated greatly, though early records are not always reliable.

[1] The lighthouse, maintained by the Commissioners of Irish Lights, has a tower 17 metres (56 feet) high and the focal height is at 84 metres (276 feet) above sea level, it has a range of 19 nautical miles (35 kilometres; 22 miles).

[1] The light was served by the steepest funicular rail track in Europe[7] from 1913 until automation.