Jul 10 1996, 10:30 am - Ruapehu Volcano

Eruptive activity at Ruapehu has continued overnight and into this morning. Incandescence was seen above the crater before dawn, and a helicopter overflight at about 09:00 (carrying Minister of Tourism John Banks) observed moderate activity with discrete pulses of ash and block emission occurring at 10 to 20 second intervals from the active vent in the southern part of the crater floor. Ash fallout was occurring on the Tukino (eastern) side of the volcano, and a gas and ash plume was being dispersed downwind to east-south-east of Ruapehu. This activity is similar to that observed yesterday.

From about 03:00 this morning, relatively large-amplitude, low-frequency volcanic tremor has commenced on the CNZ (Whakapapa) and Ngauruhoe seismographs, and is continuing at time of compiling this report. This seismicity is interpreted as generated by movement of magma and gas into and within the volcano, and suggests that continuation of eruptive activity is likely.

A COSPEC gas flight was carried out yesterday (9 July). An average discharge of 6000 +/- 1500 tons/day SO₂ was measured, compared with 5100 tons/day measured on June 28 the last measurement made. The continuing high gas discharge is consistent with the presence of a significant volume of degassing magma in the upper part of the volcano. The high gas discharge along with the forecast rainfall in the central North Island is likely to produce acid rain downwind from Ruapehu

We advise that the Alert Level remains at 3.

Ian Nairn
Rostered Volcano Surveillance Manager