New Zealand (see Geology). Star of Bengal Bank, south-southwest of L'Esperance Rock, has a least depth of . Geology The islands are a volcanic island arc, formed at the convergent boundary where the Pacific Plate subducts under the Indo-Australian Plate. The subducting Pacific Plate created the Kermadec Trench, an 8 km deep submarine trench, to the east of the islands. The islands lie along the undersea Kermadec Ridge, which runs southwest from the islands towards the North Island of New Zealand and northeast towards Tonga (Kermadec-Tonga Arc). The four main islands are the peaks of volcanoes that rise high enough from the seabed to project above sea level. There are several other volcanoes in the chain that do not reach sea level, but form seamounts with between 65 and 1500 m of water above their peaks. Monowai Seamount, with a depth of 120 m over its peak, is midway between Raoul Island and Tonga. 100 km south of L'Esperance Rock is the little-explored Star of Bengal Bank, probably with submarine volcanoes. Further south are the South Kermadec Ridge Seamounts, the southernmost of which, Rumble IV Seamount, is just 150 km North of the North Island of New Zealand. The ridge eventually connects to White Island in New Zealand's Bay of Plenty, at the northern end of the Taupo Volcanic Zone. The islands experience many earthquakes from plate movement and volcanism. Raoul and Curtis are both active volcanoes. The volcanoes on the other islands are currently inactive, and the smaller islands are the eroded remnants of extinct volcanoes. From 18 to 21 July 2012, Havre Seamount (near Havre Rock) erupted, breaching the ocean surface from a depth of more than 1100 m and producing a large raft of pumice floating northwest of the volcano. The eruption was not directly observed, but it was located using earthquake and remote sensing data after the pumice raft was spotted by aircraft and encountered by HMNZS Canterbury. The islands are seismically active. An 8.1 magnitude earthquake occurred in the early hours of 5 March 2021, leading to several strong aftershocks and a tsunami advisory on the North Coast of North Island and other Pacific islands, including Norfolk Island, Australia. Other magnitude 8 earthquakes have struck near the islands in 1917 and 1976. Environment Flora The islands are recognised by ecologists as a distinct ecoregion, the Kermadec Islands subtropical moist forests. It is a tropical and