Niue Island is a coral limestone plateau perched on top of a submerged ancient volcano near the head of the Tonga Trench. It is not part of an island chain, but it does not stand alone – there are three underwater mountains nearby.
Endeavour and Lachlan seamounts are about 30 km to the east and a third, much smaller unnamed seamount lies about 25 km to the southwest.
At one stage in the distant past, Niue was probably a coral atoll with a central lagoon. This was then exposed by falling sea levels and geological uplifts. The reef of the former coral atoll now forms the top of the rim of the island at up to 69 metres above sea level. The former lagoon is now the central plateau, which is slightly dished in shape, dropping to about 30 metres above sea level.
The coastline is rugged, with steep cliffs dropping straight into the sea, except for the west coast where there is a wave-cut rock platform 20 metres to 80 metres wide and then a very steep drop-off. The distinct shelving suggests that the island was lifted up in at least two steps.
Sources: New Zealand Journal of Geology and Geophysics Dec 1967, National Biodiversity Strategy and Action Plan of Niue, Government of Niue 2001