Pacific Ring of Fire - New Zealand

New Zealand

See also: Earthquakes in New Zealand and Volcanism in New Zealand

New Zealand contains the world's strongest concentration of youthful rhyolitic volcanoes, and voluminous sheets blanket much of the North Island. The earliest historically-dated eruption was at Whakaari/White Island in 1826, followed in 1886, by the country's largest historical eruption at Mount Tarawera. Much of the region north of New Zealand's North Island is made up of seamounts and small islands, including 16 submarine volcanoes. In the last 1.6 million years, most of New Zealand's volcanism is from the Taupo Volcanic Zone.

Mount Ruapehu at the southern end of the Taupo Volcanic Zone, is one of the most active volcanoes. It began erupting at least 250,000 years ago. In recorded history, major eruptions have been about 50 years apart, in 1895, 1945 and 1995–1996. Minor eruptions are frequent, with at least 60 since 1945. Some of the minor eruptions in the 1970s generated small ash falls and lahars (mudflows) that damaged skifields. Between major eruptions, a warm acidic crater lake forms, fed by melting snow. Major eruptions may completely expel the lake water. Where a major eruption has deposited a tephra dam across the lake's outlet, the dam may collapse after the lake has refilled and risen above the level of its normal outlet, the outrush of water causing a large lahar. The most notable lahar caused the Tangiwai disaster in December 1953, when 151 people aboard a Wellington to Auckland express train were killed after the lahar destroyed the Tangiwai rail bridge just moments before the train was due. In 2000, the ERLAWS system was installed on the mountain to detect such a collapse and alert the relevant authorities.

The Auckland volcanic field on the North Island of New Zealand, has produced a diverse array of explosive craters, scoria cones, and lava flows. Currently dormant, the field is likely to erupt again with the next "hundreds to thousands of years", a very short timeframe in geologic terms. The field contains at least 40 volcanoes, most recently active about 600 years ago at Rangitoto Island, erupting 2.3 cubic kilometers of lava.