Oct 13 1997, 11:00 am - Ruapehu Volcano

Over the weekend minor steam driven eruptions occurred within the summit crater of Ruapehu. The largest event at 2.30 pm on Sunday erupted lake floor mud and rocks to about 150 metres above the crater lake. Some of the weekends eruptions also generated tall steam columns above the volcano. There is no evidence that the eruptions discharged new lava and ash and we believe they were driven by steam and gas. These eruptions are typical of those expected from Ruapehu at Level 2.

Volcanic seismic activity peaked early on Saturday morning and has been declining since that time. The stronger seismic activity on Friday night-Saturday morning represented gas and magma moving within the volcano. Heat and gas from this magma then progressed to the surface to drive the steam eruptions observed on Saturday and Sunday.

The seismic activity was preceded on Thursday and Friday , last week, by a sequence of over 95 volcanic earthquakes. Although the seismic activity is now declining, the level of activity remains above the typical background level for Ruapehu.

The water level in Crater Lake has dropped due to increased evaporation and the small steam eruptions. This is uncovering large fumarole (gas and steam) vents on the crater floor allowing more volcanic gas to be released from the volcano.

Although we have not recorded any seismic activity that suggests a major increase in eruptive activity is likely, there remains a likelihood of enhanced eruptive activity in the next few days to weeks should magma be intruded into the volcano.

The Alert Level remains at 2.

Brad Scott (for C.P. Wood)
Volcanology Section Leader