Rabaul Update: October 6, 1994
Summary of telephone conversation between CVO staff and the USGS/VDAP team at the
Rabaul Volcano Observatory (RVO) at 1500 hr PDT on Thursday, October 6, 1994.
ALL INFORMATION IS PRELIMINARY AND SUBJECT TO CHANGE.
- Eruptive activity at Tavurvur is slowly waning.
- Chris McKee is working on a summary of the eruption so far for the GVN Bulletin;
should be available soon.
- Airfall ash from Tavurvur has taken on a greenish or whitish cast in some areas. Terry
Gerlach suspects that the greenish color is caused by elemental sulfur, produced when
sulfur dioxide and hydrogen sulfide released from cooling ash combine to form sulfur and
water. The whitish color may be anhydrite, gypsum, or thenardite (sodium sulphate).
- Probably on September 26 or 27, a COSPEC measurement suggested that the sulfur
dioxide flux from Tavurvur was about 30,000 tonnes/day.
- Airfall ash from Tavurvur consists of a basal, light gray layer overlain by a thicker,
chocolate brown layer, in turn overlain by a thinner light gray layer. No chemical data
are available yet.
- Yesterday, the VDAP team installed a seismometer at Talawat (sp?), a spit of land
southeast of Tavurvur.
- A few, small, high-frequency seismic events are occurring near Vulcan.
- Four seismic stations are now part of the Willie Lee system. The team will install a
repeater today for the Talawat station, which will bring the number of new stations to
five. In addition, there are two surviving RVO stations which are not yet part of the
Willie Lee system.
- Dry tilt measurements near Matupit Island indicate that the deflation rate there is slowing
and approaching the limit of detection.
- No new leveling results are available since yesterday.
- There is some concern that the Burma road, which extends southeast from RVO to
Kokopo, will be rendered impassable by mudflows during the first heavy rain.
- Australian volcanologist Wally Johnson is expected to arrive at RVO today.
The following corrections to our October 3 update and other information are from Jim Mori, who
talked to Chris McKee on Thursday, October 6.
- The tide gauge that was lifted out of the water on the first day of the eruption was near
Vulcan, not Matupit Island as reported earlier. This location may be similar to that of an
uplifted coral reef seen before the 1937 eruption.
- The magnitude 5.1 earthquake that heralded the start of the eruption was on the eastern
side of the ring fault. Later in the day, seismicity moved toward Vulcan and the Beehives
on the west side of the ring fault.
- RVO declared a Stage 2 alert at 6 p.m. local time on Sunday, September 18, and a Stage
3 alert at 8 p.m. that night. The eruption began about 6 a.m. the following morning.