Blast from the past teaches lessons

TOWERING INFERNO: Ruapehu erupting in 1995 with The Chateau in the foreground. A_HBT1995TWERUPT

It is 20 years since Ruapehu began a series of spectacular eruptions that lasted for over a year.

Scientists, emergency managers, conservation staff, iwi and university students will gather at Whakapapa Village later this week for an event to mark the 20-year anniversary of the 1995-96 eruptions.

Starting in the winter of 1995, the series of spectacular eruptions at Ruapehu became the biggest volcanic event in New Zealand for 50 years, capturing worldwide media attention. Fortunately, the major eruptive activity occurred while the ski areas were closed, so there were no deaths or serious injuries, but stock were lost and airports and roads had to close.

The event takes on special significance as this year is also the 40th anniversary of the 1975 Ngauruhoe eruption and the 70th anniversary of the 1945 Ruapehu eruption.

On August 14, the Volcanic Science and Risk Management Workshop will feature a range of science presentations and activities to reflect on two decades of progress in managing eruption hazards and risks in Tongariro National Park.

As part of the programme, a public talk is scheduled for August 15 at 6.30pm, at Lorenz's Bar and Cafe at the top of the Bruce Rd, Whakapapa.

It will be presented by Joint Centre for Disaster Research director David Johnston and examines the social impact of volcanic hazards.

"We believe this is a great opportunity to reflect on two decades of progress in monitoring, scientific understanding, risk management and social science," Dr Johnston says.

GNS Science volcano information specialist Brad Scott says that, in spite of its picture postcard appearance, Tongariro National Park is a highly active volcanic centre, and it would be foolhardy to think of it simply as a benign outdoor playground.

"In 1954, Mt Ngauruhoe produced lava flows, and in 1974 and 1975 it produced explosive eruptions," he said.

"Eruptions from Ruapehu in 1968, 1969, 1971, 1975, 1977, 1988 all produced lahars, as did the 1995-96 eruptions.

"More recently there was the major breakout lahar from the Crater Lake in 2007, which was more hazardous than the 1953 Tangiwai Railway disaster event. Then in 2012 there was an eruption episode from Te Maari Craters on Mt Tongariro, which closed the popular Tongariro Alpine Crossing track for seven months."

On the plus side, the central North Island volcanoes are better monitored than ever with seismographs, GPS and web cameras placed throughout the National Park by the EQC-funded GeoNet project, keeping a close watch on the volcanic pulse of the area.

In addition, GeoNet's volcano teams regularly visit active areas such as Ruapehu's Crater Lake, Ngauruhoe's crater and the Te Maari Craters to collect water samples for analysis and to check temperatures. This is important for tracking long-term trends and picking up early signs of unusual behaviour or volcanic unrest.

The steady flow of monitoring data enables the Department of Conservation and other agencies to respond quickly to manage the risks.

DoC volcanic technical adviser Harry Keys says sudden volcanic events may still pose serious risks to people close to the active vents. But he added that the lessons of the past two decades had led to huge improvements in the ability to manage volcanic risks.