Caldera boundaries of the Maroa Volcanic Center with lava types, vent locations and structural features. Modified from Cole (1990) after Cole (1986).
The Maroa caldera is defined by a negative gravity anomaly that indicated a depression in the basement rock over an area of 15 x 10 miles (25 x 16 km). This area contains numerous simple and compound lava domes. There is no conspicuous topographic depression associated with the caldera. The caldera probably form during four eruptions from 230,000 to 140,000 years ago that produced small volumes (less than 10 cubic km each).
The caldera contains at least 70 domes or flows, most younger than 140,000 years old. Single domes range in size from 300 m to 3 km across. The largest dome complex covers an area of 45 square km. Total volume of exposed lava is 24 cubic km (Houghton and others, 1994). There have been at least four small volume basaltic eruptions at Maroa caldera.
The only recent eruptions were phreatic explosions in about 7050 BC and 180 AD. These eruptions produced a tuff ring and lava dome at Puketerata.
On 30 March, a moderate-sized hydrothermal explosion occurred in the Alum Lakes area, Wairakei, destroying trees and other vegetation near the crater. The water levels at several of the Alum Lakes had dropped several weeks prior to the explosion.
This information was summarized from Smithsonian Institution's Preliminary Notices of Volcanic Activity.
Houghton, B., McPhie, J., and Simmons, S., 1994, Physical volcanology and modern geothermal systems; Field Guide 1 North Island, New Zealand: Masters of Economic Geology Course Work Manual 8, Centre for Ore Deposit and Exploration Studies (CODES), University of Tasmania.
Wilson, C.J.N., Houghton, B.F., and Lloyd, E.F., 1986, Volcanic history and evolution of Maroa-Taupo area, central North Island, in Smith, I.E.M., ed., Late Cenozoic Volcanism in New Zealand, Royal Soc. New Zealand Bull, 23, p. 194-223.
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