Ruapehu eruption fades to Alert Level One

Ruapehu Bulletin, Volume 14, Issue 657, 8 October 1996, Page 3

Ruapehu eruption fades to Alert Level One

Scientists lowered their eruption status of Ruapehu to Alert Level One last week, after several weeks of low level of activity in the crater. "Although several of the parameters that we record and use to make an evaluation of the status of the volcano remain at higher levels than they were before the enhancement of activity in June 1996, they have all been at uniform levels for some time," said vulcanologist Brad Scott from the Institute of Geological and Nuclear Sciences (IGNS), Wairakei. "At present, these levels are now defining the current 'background state' for Ruapehu and in effect the baseline has been moved." Ash falls Minor ash eruptions occurred on 1-2 September and possibly again on 9 September. These were minor, although the 2-3 September activity was enough to close down T uroa ski fields. Since 9 September no ash cmissions have been reported and seismic activity has been at relatively low levels, except on 29 September when a shortlived period of volcanic tremor was recorded. No eruptive activity followed. T wo small ponds are now forming on the floor of the crater that was active in 1996. The higher pool is overflowing into the lower one. Recent measurements show an output of 1 700 tons perdayofSO , significantly down from 2the previous measurement of 5500 tons per day. Together these observations indicate a decline in activity to 'background levels', said Mr Scott. "Mt Ruapehu continues to be an active volcano and this change in alert status must not be interpreted to mean that there will be no further eruptions. The current eruptive episode (post17 June 1996) appears to have ended but some hazardous areas remain on the volcano. The summit crater area in particular remains hazardous and isolated explosive eruptions could still occur without useful warning signs. The active crater area should continue to be treated with respect, warns IGNS.