Where it is and what it carries
The Kermadec Plate covers about 505,000 km² and stretches from just south of Tonga to New Zealand’s North Island. Most of it is seafloor along the Kermadec Ridge and the volcanic Kermadec Arc, which reaches the surface at the Kermadec Islands. In the south it includes about 19% of New Zealand: the eastern part of the North Island, including the East Cape and Gisborne.
Many maps include this region in the Australian Plate. PB2002 separates it because the Havre Trough, a back-arc basin west of the Kermadec Ridge, is opening and lets the arc move on its own.
What happens at its edges
The 2,388 km boundary with the Pacific Plate is all subduction. In the north it follows the Kermadec Trench, one of the deepest trenches on Earth, and in the south the shallower Hikurangi Trough off the North Island. Relative speeds average about 7.8 cm/yr, falling from about 13 cm/yr in the north to about 3.1 cm/yr in the south. The Hikurangi margin is slower partly because the Pacific crust there includes a thick oceanic plateau.
The 2,219 km boundary with the Australian Plate opens behind the arc. Offshore it is the Havre Trough, with spreading and rifting. On land it continues as the Taupo Volcanic Zone, where the crust of the North Island is stretching. Relative speeds average about 2.6 cm/yr, from under 1 cm/yr in parts of New Zealand to about 5.9 cm/yr in the north.
At its northern end, the plate meets the Tonga Plate along a short transform boundary at about 3.9 cm/yr.
Earthquakes
The dataset lists 143 earthquakes of magnitude 6.5 or larger since 1900, two of them magnitude 8 or more. The 2021 Kermadec Islands earthquake (M8.1) is the largest, followed by the 1976 Kermadec Islands earthquake (M8.0). Others include M7.7 in 1986 and M7.6 in 2011 near the Kermadec Islands, and a deep M7.8 quake at 153 km south of Fiji in 2007.
Off Gisborne, two quakes in 1947, M7.7 in March and M7.6 in May, produced tsunamis much larger than expected for their size. Geologists call events like these tsunami earthquakes.
Volcanoes
The plate holds 18 volcanoes in the dataset, many of them underwater. Raoul Island in the Kermadec group erupted in 2006, and Monowai, a submarine volcano, in 2014. In 2012, the Havre Seamount erupted deep underwater and released a vast raft of floating pumice. In New Zealand, the Okataina volcanic center produced the 1886 Tarawera eruption, and Whakaari/White Island, often called New Zealand’s most active volcano, has erupted as recently as 2026.