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The New Zealand to Fiji Region
After the Indian Ocean, the CAVW regions begin a long clockwise circuit around the Pacific Rim starting with New Zealand. The Pacific's 'Ring of Fire' has produced about two-thirds of the world's Holocene volcanoes and their dated eruptions, largely by subduction of the huge Pacific plate and several smaller plates. The New Zealand to Fiji region is geographically small but volcanologically important. Its total land area is only 292,000 km2 (the size of Arizona) and its population of 5.4 million is roughly comparable to greater Philadelphia. New Zealand makes up 92% of the land area and three-fourths of the region's population, but its Holocene volcanoes are restricted to North Island and offshore areas north to the Kermedec Islands.
Estimates of Maori arrival in New Zealand range from 800 AD to 1350 AD, and the first European to sight the islands was probably Tasman in 1642. Written records, however, were not kept until whalers started to land in the 1790s, and detailed record-keeping began with the missionaries in the late 1810s. The earliest historically-dated eruption in New Zealand was at White Island in 1826. The first permanent settlement (Wellington) and the Maori treaty (ceding sovereignty to England) came in 1840. The Kermadec Islands, totaling 34 km2 in area, were annexed to New Zealand in 1887, and a small research station is maintained there.
New Zealand contains the world's strongest concentration of youthful rhyolitic volcanoes, and voluminous ignimbrite sheets of the many calderas of the Taupo volcanic zone marking the boundary of the Australian and Pacific tectonic plates blanket much of North Island. Taupo volcano itself, a topographically subdued caldera largely filled by Lake Taupo, produced one of Earth's largest Holocene eruptions in about 180 AD, as well as Earth's most recent VEI 8 eruption that ejected more than 1100 km3 of ash and pyroclastic flows about 23,000 years ago. A strong emphasis on tephrochronology has documented the Quaternary volcanic history of this active island in unusual detail. This region has a high percentage of eruptions producing pyroclastic flows (nearly 10%, mostly on New Zealand's North Island), which underscores the potential risk for New Zealand eruptions. It is also near the top of regions with crater lake eruptions, primarily due to the frequent eruptions from Ruapehu's crater lake. In collaboration with New Zealand colleagues, we have reorganized the North Island volcanoes in an effort to achieve a closer genetic identification of each center.
The Kingdom of Tonga is an archipelago of two parallel island belts: that to the east is low, fertile, coralline, and well populated, while that to the west is young, volcanic, and ranges from steep cones to ephemeral islands. The unbroken line of subduction, from NZ through the Kermadecs and Tonga, ends abruptly and the trench swings west north of the remarkable, donut-shaped island of Niuafo'ou, a basaltic shield volcano with a large, lake-filled caldera. European contact with Tonga began in the 17th century and Captain Cook named them the Friendly Isles in 1773; the first recorded eruption was in the next year.
The Samoan islands are formed by a hotspot to the NE of the Tonga-Kermadec-NZ subduction zone, and are volcanically distinct from their neighbors. They were invaded by Fijians in the early 13th century, but may well have been settled thousands of years earlier. European contact was first made by the Dutch in 1722, but detailed record keeping began with the arrival of missionaries from London in 1830. The 1725 eruption of Savai'i, covering 190 km2 with 2 km3 of lava, was the first historical volcanism in region 04. In 1900 the islands were divided, with the smaller western islands going to the US and the larger, more populated, and more volcanic western islands going to Germany. New Zealand annexed Western Samoa and administered it from 1914 to 1962, when it became independent.
The three Holocene centers of Fiji form smaller islands NE to S of the two largest islands that support 90% of the population. The archipelago was populated for thousands of years by Polynesians, but the Dutch began European exploration in 1643, and it became a British crown colony in 1874 before achieving independence in 1970. Although not in the CAVW for Region 04, Fiji was added by us in 1981 upon recognition of its Holocene volcanism.
Much of the region north of New Zealand's North Island is made up of seamounts and small islands, including 16 submarine volcanoes with sufficiently recent activity to be included in the 2nd edition of this compilation. Many more seamounts exist along the Kermadec-Tonga arc, and we have added a half dozen more submarine volcanoes in this edition. Recent bathymetric studies have begun to document the widespread distribution of submarine volcanoes and discovered many with active hydrothermal activity. In 2009 an ongoing eruption was observed at a submarine volcano at the northern end of the Tonga arc, and a new lava flow from an eruption in late 2008 was documented at a vent on a nearby Lau Basin back-arc spreading center. This high level of submarine activity is seen in the fact that this region has the largest number of eruptions dated by SOFAR technology, or underwater sound, and no other region has a higher proportion of eruptions building new islands. More than one sixth of all eruptions in Tonga and the Kermadecs have produced new islands, most recently in 2006 at Home Reef and 2009 at Hunga Tonga-Hunga Ha'apai. Many of these 'jack-in-the-box' islands are composed of pyroclastic deposits that are quickly eroded below sea level by wave action.
List of Holocene volcanoes in the New Zealand to Fiji region.