May 19 1998, 11:15 am - Ruapehu Volcano

Since May 9 we have continued to record volcanic earthquakes at Mt. Ruapehu. Although the Crater Lake changed colour over night May 11 - 12, no other activity has been reported. In the last 24 hours the Tongariro volcano-seismic network has recorded 3 moderate sized volcanic earthquakes, each of 2 - 3 minutes duration. The event at 09:45 today is the largest to date in the sequence. Volcanic tremor levels rose slightly May 9 to 12, but have been near typical background levels since May 17, with no apparent response to the volcanic earthquakes.

The Crater Lake was overflown on May 15, it was dark grey in colour, with some steam rising off the surface. There was no sign of vigourous convection within the lake or any ejecta about the shoreline. Observers on the mountain today have not reported any activity. No steam plumes have been reported at the volcano.

Summary

A sequence of volcanic earthquakes continues to occur at Ruapehu. No significant changes are apparent in the volcanic tremor. Except for a change in the colour of the Crater Lake overnight May 11-12 no activity has been reported from the crater.

These data are insufficient to warrant a change in the alert level. The current changes are less than those which have preceded past eruptions.

We advise the Alert Level remains at Level 1.

Brad Scott
Volcano Surveillance Manager