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.