The Kermadec–Tonga subduction zone is a convergent plate boundary that stretches from the North Island of New Zealand northward. The formation of the Kermadec and Tonga plates started about 4–5 million years ago. Today, the eastern boundary of the Tonga plate is one of the fastest subduction zones, with a rate up to 24 cm/year (9.4 in/year).[1] The trench formed between the Kermadec–Tonga and Pacific plates is also home to the second deepest trench in the world, at about 10,800 m,[2] as well as the longest chain of submerged volcanoes.[3]