Diary of an eruption

Ruapehu Bulletin, Volume 13, Issue 612, 14 November 1995, Page 7

Diary of an eruption

The following reports on the volcanic eruption activity on Mt Ruapehu are taken from daily media releases from the Institute of Geological and Nuclear Sciences Wairakei Research Centre: v Monday 6 November, 4.00pm Activity on the volcano was continuing at a low to modest level. Very little volcanic tremor had been recorded and the base level of seismic activity was low to moderate. Large amounts of gas were being discharged, which led to the alert status remaining at Level Three. Tuesday 7 November, 4.00pm Similar to the previous day's report, with high gas output confirmed. Wednesday 8 November, 4.00pm Activity continued at a low level with very little volcanic tremor occurring but still large amounts of gas produced. IGNS parties completed tilt-levelling survey on the Dome (at the summit), sampled tephras and scoria bombs from the Dome and Summit Plateau near Te Heuheu and studied the recent secondary lahar deposits in the Mangatoeteonui catchment. They had sampled the top 1 .5m of tephra at the old Crater Lake outlet on 3 November. The tilt-levelling survey indicated that no major inflation of the summit area could be "identified at this stage of the 1995 eruption". Thursday 9 November, 4.00pm Seismic activity had changed significantly since 10.00am. Volcanic tremor was recorded at the Dome as well as numerous explosion eruption earthquakes. The weather stopped confirmation of the size or style of the activity. No reports of ashfall were reported. Friday 10 November, 4.00pm The seismic activity was characterised by weak volcanic tremor, with the high frequency "eruption earthquake signatures" of the previous day absent. Weather kept ground parties away. As of 7 November the sulphur dioxide gas flux was 2100 tonnes per day. Saturday 1 1 November Weak volcanic tremor was recorded with no high frequency eruption earthquakes. Bad weather precludedvisual observations. Sunday 1 2 November, 5.00pm Seismic activity was low but significantly higher than earlier in the week. Tremors accompanied emissions of significant gas and minor ash. Aircraft reported a gas cloud drifting north of Napier up to 2000 metres on 4 Saturday evening. Ground parties reported near-continuous gas emissions. Some moved downwind into the Whangaehu Valley. An aerial inspection by IGNS staff reported continuous emission of gas and steam from the northern vent within the crater. Minor slumping had occurred in the area of the former outlet of Crater Lake. Rapid melting of recent snow was occurring. The alert level remained at three all week.