Significant progress has been made in the monitoring of volcanic activity since the 1995 Mt Ruapehu eruption.
It was that technology which was discussed by scientists, emergency managers, conservation staff, iwi and university students who gathered at Whakapapa Village over the weekend to mark 20 years since the beginning of the series of eruptions on the mountain.
In 1995 and 1996, Mr Ruapehu ejected a total of 60 million cubic metres of acidic ash into the sky, which blanketed land up to 300km from the mountain, irritating eyes and throats in the Central North Island. The ash damaged machinery and cars' paintwork, contaminated rivers and water supplies, ruined crops, closed state highways, shut airports and killed livestock.
Electricity suppliers were hit with multimillion-dollar losses as ash shorted out power pylons and severely damaged turbines in the Rangipo power station. At times, the ash plume reached as high at 10km, causing a significant aviation hazard.
The eruptions were similar in size to those in 1945, but their social and economic impacts were much greater.
In 1945, there was just one ski area and no ski lifts on Ruapehu but by 1995, there were three ski areas and 36 ski lifts. By the mid-1990s, there were up to 10,000 people on the mountain on some days during winter.
On Friday, the Volcanic Science and Risk Management Workshop featured a range of science presentations and activities to reflect on two decades of progress in managing eruption hazards and risks in Tongariro National Park.
Volcano Information Specialist at GNS Science, Brad Scott, said, that despite its picture postcard appearance, Tongariro National Park was a highly active volcanic centre and it would be foolhardy to think of it as a benign outdoor playground.
Monitoring was now better than it had been with seismographs; GPS and web cameras placed throughout the park by the EQC-funded GeoNet project, keeping a close watch on the volcanic pulse of the area.
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 and check temperatures. The steady flow of data enables the Department of Conservation and other agencies to respond quickly to manage the risks.
Volcanic Technical Advisor at DoC, Harry Keys, said sudden volcanic events still pose serious danger to people close to the active vents but lessons of the past two decades had led to huge improvements in the ability to manage volcanic risks.