Smithsonian Institution
Global Volcanism Network Bulletin v. 20, no. 3, March 1995

Rabaul (Papua New Guinea)  Mild explosive activity at Tavurvur

New Britain Island, Papua New Guinea
4.27S, 152.20E; summit elev. 688 m
All times are local (= GMT + 10 hours)

"Explosions at Tavurvur were mostly mild with emission clouds
rising slowly to ~1 km above the crater at intervals of ~5-15
minutes. Seismic activity was slightly elevated on 1-2 March, but
then decreased sharply in accord with weaker visible activity. The
activity remained low for 24 hours then started to increase at a
steady rate until it peaked on the 6th. Activity decayed the
following day, but then began a gradual recovery that continued
until 14 March. The explosions continued at intervals of ~5-15
minutes with ash emissions lasting 2-5 minutes. On 15 March a
slight increase in seismic activity occurred as indicated by larger
and more frequent explosion earthquakes, although visible activity
appeared unchanged. Seismicity peaked on the 19th and then declined
slightly over a period of ~48 hours. During the next 10 days the
activity showed minor fluctuations but on average there were ~6
events/hour. On 30 March at 0805 and 2034 two strong explosions
occurred. Dense ash clouds rose ~3 km above the crater and the
flanks of Tavurvur were showered with lava fragments. These
explosions signified a dramatic change in the pattern of activity
as the frequency of explosions dropped markedly. The intervals
between explosions sometimes lasted several hours.

"Aerial inspections of Tavurvur and Vulcan were conducted on 6, 13,
and 21 March. The active crater at Tavurvur was bowl-shaped. On two
occasions (6 and 21 March) there appeared to be an ash-mantled lava
mound on the floor of the crater. At the NW and SE edges of the
mound were a number of small vents (~1-2 m wide). These vents were
aligned roughly in two arcs, which might represent small fissures.
Between eruptions some vents emitted blue vapour. When inspected on
14 March, three rubble-covered vent areas were noted on the S, E,
and NE parts of the crater floor. Low ridges of ash separated these
vents. Weak fumaroles were present on parts of Tavurvur's main
crater, especially on the N Wall. Fumarolic activity was also noted
on the 1994 lava flow.

"Apart from the seismic activity related to events at Tavurvur,
which were basically low-frequency explosion earthquakes, overall
seismic activity of Rabaul Caldera was very low. Only five
well-located high-frequency earthquakes were recorded (compared to
4 in February and 28 in January). Three occurred outside the
caldera and the other two were under Tavurvur. The electronic
tiltmeter at Matupit Island continued to show a trend of slow
deflation of the caldera.

"Vulcan continued to exhibit only weak fumarolic activity at the W
base of the 1994 crater. Hot springs along the N shore yielded
temperatures of about 100 deg C. Rabaul continued to be under a
State of Emergency with access to severely affected areas being
controlled because of the risk of mud flows and flooding. Since the
eruption started in September 1994, only one death was reported
related to flooding."

Information Contact: same as for Manam.