Kermadec-Tonga Subduction Zone

The Kermadec-Tonga subduction zone is a convergent plate boundary which stretches from the North Island of New Zealand northward, and includes the Hikurangi Trough, the Kermadec Trench and the Tonga Trench. Along this zone, the Pacific Plate to the east is subducting beneath the Indo-Australian Plate at a rate of 5.5 to 7.4 centimeters per year.

The southern end of the subduction zone transitions to a right lateral-moving transform fault south of the North Island called the Alpine Fault.

The subduction seems to be driven primarily by the excess weight of the cold/old oceanic plate entering the hot mantle of the Earth.