Macauley Island is 3.06 km (1.181 sq mi) in area, including neighbouring Haszard Island, which is 220 m (722 ft) to the east and about 5 ha (12 acres) in area. Macauley's highest point is 238 m (781 ft) Mount Haszard, and it forms part of the rim of a caldera centred 8 km (5 mi) to the north-west, atop a large submarine volcano. The volcano's last eruption was in 4360 BC ± 200 years.