'Hiss & roar' time for volcanoes

Ruapehu Bulletin, Volume 12, Issue 574, 21 February 1995, Page 10

'Hiss & roar' time for volcanoes

Earthwatch Earthwatch is a summary ofvolcanic, earthquake and geothermal activity in the Taupo Volcanic Zone. This summary is based on studies and observations by Institute of Geological & Nuclear Sciences staff from Wairakei Research Centre and Kelburn (Wellington), observations by tour operators and Department of Conservation staff.

The year started with such a hiss and a roar for the Taupo Volcanic Zone that it is difficult to focus on any one aspect. As Mount Ruapehu is the tallest mountain in the North Island, perhaps that's as good a place as any to start! Crater Lake at Mount Ruapehu continued to heat with the temperature exceeding 50 degrees Celsius attheendofJanuary. Many small geyser-like phreatic eruptions have been observed by people climbing the mountain. Since 1960 the temperature of Crater Lake has only exceeded 50 degrees Celsius on four occasions, July-August 1966, April-June 1968, May-Au-gust 1971 andJamlary-Feb-ruary 1982. There has been a lot of discussion recently about earthquakes, and the Taupo Volcanic Zone has continued to produce its share. This is particularly reward-

ing for seismologists who have undertaken a detailed experiment using over 40 portable instruments in the area between Taupo and Rotorua. Earthquakes which have been felt occurred in Tauranga, Whakatane, Rotorua, Taupo and Tongariro area during January — not a significant increase, but slightly more than usual. In the shadow of the Kobe earthquake in Japan — those who relaxed in front of TV on Monday 6 February watching the cricket were able to experience a magnitude seven event at 200km distant. Also during January the Earth Deformation group were busy remeasuring the

size of Okataina Volcanic Centre, and the width of the Taupo Fault Belt south of Rotorua and north of Lake Taupo. They were using the-Global Positioning Satellite (GPS) system to conduct this work. The GPS system allows relative po-

sitions of stations 150200km apart to be determined to 5 or 6mm accuracy. Inferno Crater at Waimangu also started out in 1995 by deviating from its normal cycle. It overflowed nine times in January, usually only overflowing once every 38 days. Each overflow has lasted five to six hours, whereas the typical overflows last 40 to 50 hours. Thistypeof activity has occurred before at Inferno Crater.