Where it is and why it is separate
The Niuafo’ou Plate covers about 124,000 km² of the northern Lau Basin, the back-arc basin that lies between the Tonga islands and Fiji. It is named after Niuafo’ou, a volcanic island that belongs to Tonga.
The Lau Basin opens because the Pacific Plate sinks so fast at the Tonga Trench that the arc above it is pulled east, away from Fiji. In the south the basin opens along a few long spreading centers. In the north the pattern breaks up into short ridges, rifts and transform faults. Seafloor mapping and earthquake patterns outline a separate block there, and PB2002 calls it the Niuafo’ou Microplate. Its exact edges are still uncertain, and other studies divide the northern Lau Basin into different pieces.
What happens at its edges
All four boundaries are divergent, which means new crust forms around much of the plate. The longest, 767 km, is with the Tonga Plate to the east. It is mostly rifting with some spreading ridge, and relative speeds vary from under 1 cm/yr to about 12.6 cm/yr, averaging about 6.2 cm/yr.
To the west, the plate separates from the Australian Plate along 551 km of spreading ridges, rifts and transforms, at about 8.3 cm/yr. In the north, it spreads from the Pacific Plate at about 13.7 cm/yr, one of the fastest divergent motions in the PB2002 model. In the northwest, it pulls away from the tiny Futuna Plate at about 10.9 cm/yr.
Earthquakes and volcanoes
The dataset lists 17 earthquakes of magnitude 6.5 or larger since 1900, none reaching magnitude 8. The largest, M7.5 in March 2026, struck 234 km deep, about 158 km west of Neiafu. Several others, including an M7.05 quake in 1972 and M6.9 quakes in 1989 and 2023, struck at similar depths of 220 to 235 km. All of these lie in the Pacific slab sinking beneath the basin. Shallower quakes, such as the M6.7 events of 1991 and 2014 near the plate’s northern edge, come from its own spreading and transform boundaries.
The dataset lists three volcanoes on the plate. Niuafo’ou is the best known. It last erupted in 1946 and rises only 260 m above sea level, but it is the top of a large volcano built on the basin floor.