Ruapehu - IGNS - Science Alert Bulletin V96/11

June 18 1996 (Tuesday) 1145 NZST (UT + 12)

Ruapehu Volcano


A significant lava (strombolian type) eruption occurred at Ruapehu last
night between 2100-2200h. The eruption was characterised by loud
detonations and sprays of glowing rocks ejected above the crater. The
eruption event was accompanied by strong seismicity.  Since that time the
level of seismicity has declined. Through to about 0300h several discrete
eruption earthquakes were recorded, but the size and number per hour has
continued to decrease through to the present time.

Observations made on overflights this morning (courtesy of TVNZ and TV3)
confirm that the new lake has been destroyed and the crater floor is dry.
The active vent is an icecream cone shaped feature in the southern part of
the crater floor.  Apparently thick deposits of lava (bombs and lapilli)
have accumulated on the crater floor.  The bombs and blocks thrown out
over night travelled further than those erupted yesterday, out to about
1.5km from the vent. Dome Shelter remains intact, as does the seismic
signal from the shelter.

Presently the active vent is producing weakly ash-charged plumes to
1000-2000m above the summit, which are blown down wind forming a low level
(5-10000 ft) haze.

The level of volcanic tremor on the Chateau record remains elevated and
low frequency in content. This suggests that molten material continues to
move into the base of the volcano.  While this activity continues, the
possibility of further activity remains high.

The alert level remains at 3.

In summary, the style and scale of activity remains similar to that in
mid- October 1995.

BJ Scott for CJN Wilson  (Volcanology Programme Leader)