Ruapehu crater bulges, still off limits

Ruapehu Bulletin, Volume 13, Issue 630, 2 April 1996, Page 1

Ruapehu crater bulges, still off limits

Visitors to Mt Ruapehu are strongly advised not to climb to the Dome Peak at present. The area within 800 metres of the centre of the crater may be at increased risk from explosions throwing out rocks over this distance. Dome Peak and Shelter and the crater basin are all within 800 metres. The reason for this renewed concern is that a small island has appeared near the western shore of the new Crater Lake. This island is the top of a dome of solidified lava pushed up from beneath the lake. Steam and gas are escaping vigorously around it and to the south towards the areaof most powerful fumaroles (steam vents) in the crater. The island is often obscured by steam but is thought to be about 1 5 metres high and 20 metres across at present. The emergence of this feature indicates that Ruapehu' s recent eruptive phase is not yet over. The lava dome was flrst sighted Tuesday last week by IGNS research party members working in the summit area. "Observers have reported vigorous steam and gas emissions and sediment-laden geysering about the margins of the extrusion," stated Bruce Scott, IGNS volcanology programme leader. "The extrusion process has been passive to date," he said. An apparant increase in high-frequency volcanic earthquakes, running at 20-60 per day since 25 February indicated that the "extrusive activity has been oc'curring passi vely since late February" but until no w concealed under the lake.

As a result of the low level of activity by comparisOn to September - October 1995, the alert level on the mountain is at Level 2. "This should not necessarily be interpreted to mean either that the present eruption episode has ended or that there are no hazardous areas on the volcano. The possibility of isolated explosive eruptions occurring without useful warning signals has always been present," said Mr Scott. Dr Harry Keys, advisory scientist for the Tongariro/Taupo Conservancy of the Department of Conservation said "scientists need time to assess whether the dome-forming process remains passive as it has been for some time, or whether explosive activity will develop." Ruapehu Alpine Lifts will not be taking guided parties to the Dome in the meantime. Some people may want to climb up by themselves to look for the new island. "We urge them not to" said Dr Keys. 'The island cap't be seen from Dome anyway". The Department of Conservation is in close communication with vulcanologists at the Institute of Geological and Nuclear Sciences at the Volcano Observatory regarding public safety. A further media release would be made this week regarding access during the Easter holiday period, he said. Intending visitors should phone or visit Department of Conservation offices around the mountain for up-to-date information about volcanic activity, weather and other conditions on the mountain.