Scientific Endeavours and Achievements

To eliminate the possibility that the observed delay to seismic waves from strombolian explosions was caused by thick and/or very low velocity layers under the recording stations on the flanks of the volcano, a seismic refraction line was run between the warm ground in the Side Crater near El, and the somma rim at the edge of the summit plateau near CON station (at Truncated Cones). El is a first order trig station, and CON transmitting antenna is 20m from an aerial photography "field station" marker. Running the seismic line revealed a 272.7m mistake in the survey position of Con station, which has now been revised to 77 deg 32′ 04,68″ S, 167 deg 05′ 06.54″ E. The effect wi11 ripple through al1 previous seismic results.

We flew to the Fang Glacier acclimatization camp in 2 lifts on 23 November after servicing al1 the equipment at Scott Base, and reinstalling the NSF telemetry receivers in place of the Victoria University ones. The NSF equipment was provided by S–O81 so that Erebus could continue to be recorded by NIPR equipment.

During the 3–day acclimatization at Fang, trips were made to replace a faulty seismometer at MAC station, to retrieve batteries page 3 from the TV station for use in the refraction survey, and to check out the toboggan route to the lower hut. We commenced the seismic survey on 29 November, drilling all the holes at the south end of the line, and shooting spread one from the south end. Leaving the spread with the Nimbus seismograph in a heated insulating box inside a dome tent, the party moved explosives, drill, and shot-firing/transmitting equipment to the upper hut with the Grizzly. On 30 November, Nick and Brent drilled all the shot holes in the side crater and fired two shots. Ray and Alla recorded the first on spread one and shifted to spread 2 for the second. On 1 December, spread 2 was shot from CON, and the whole team shifted the spread and recording site to spread 3, which Nick and Brent shot first from the Side Crater, and then from COM to complete the line. Completing in 3 days was an excellent achievement by Nick and Brent, and I wished we had taken more explosive to extend the work. The seismic arrivals were weak, and radio switching noise affected the digital recordings until we changed to clearing the record memories after giving the a "fire in 5 seconds" command, Our preliminary result is stated in the abstract.

After a rest day and a windy day, we brought down 3 more batteries from the TV station, and then on 5 December retrieved the buried electromagnetic loop Hire shown on L & S map 1253. Only about 60% of it could be pulled up, because it had been chopped up, displaced, and further buried by the eruptions of 1984. Our field assistant judged that NSF cables and buried batteries, abandoned at the summit after damage in the 19S4 eruptions, had higher priority. We had no authority from NSF, and it usurped a second trip to the summit planned by a Scott Base recovery team, but majority ruled, and we spent 2 days returning about 200 kg of Carbonnaire batteries to the upper hut, and spiral–4 cable to the 1ower hut. Again this was a remarkab1e achievement by Nick and Brent.

On 8 December we visited the Sauna Cave 470m from El in Azimuth 199 deg.E at spot height 3569.3m on L & S map 1253. Access is via a 15m deep shaft at the base of an impressive ice tower, and the rock cave (an old lava tube) underlies the source of the fumarole feeding the tower. The rock roof in the upper reaches of the cave is uncomfortably hot to touch, and the air is good and hot. Later that day we set out to retrieve the TV station but the 16 day spell of fine weather ended suddenly with blowing snow and dark cloud.

December 9 and 10 were also poor, but the CON transmitter was brought in and the VUW preamp/VCO removed from it. Reinstallation on 11 December showed that the mountain was clear except at the lower hut, and we were able to retrieve the TV station, except for one load left at the toboggan terminal in Ray's Gully when Brent reported his ring finger frozen nearly to the first joint. He had a chemical hand–warmer with him, but didn't appreciate the problem until he took his glove off. We applied the rapid warm–up treatment, and confined Brent to the heated hut. The finger blistered badly, and the nail came off, but it has since healed satisfactorily.

December 12 was bad, and we rescheduled our descent for the 14th, and began a 24 hour watch. Clearance at 2:30am on 13th page 4 enabled us to complete the TV retro, and remove the 2 VUW preamp/VCO's from the Ei station, and so we were ready to descend on 14th. However, an orographic cloud cap Formed, and persisted until the 20th, when Gentle 10 miraculously found its way through the clouds, and took all 4 of us off without any gear. Two more flights brought dawn most of the gear and rubbish, but much of the VUW equipment remained on the mountain, even though it had been carefully sorted and flagged.

Brent, Alla and Nick barely had time to pack their own gear before their scheduled departure on 21 December (held over to the next morning due to lack of a backup aircraft), but the major task of packing the VUW equipment from the mountain and the lab for shipment to another volcano remained to be done. The cost to VUW and myself of removing the abandoned NSF gear was now apparent. DSIR Antarctic kindly rescheduled my return flight and by working all hours, including three flights with S-081 (at their expense) to recover the remaining equipment at the lower hut, and the camp at Fang, I completed the packing with an hour to spare before my return f1ight on 27 December.

The Erebus program remains one of excellent international cooperation. but this season Phil Kyle of S–081 went up Erebus after our descent, and Katsu Kaminuma could not arrange funding-tor a Japanese collaborator.

Often disguised by our field event program, has been the work of maintaining a major recording facility in the Scott Base lab, and of processing the data from a whole years recordings. The processing is shared between Prof Katsu Kaminuma of N1PR Tokyo, who locates most of the earthquakes, and myself and Mr O'Brien (M.Sc. candidate) who have been studying the explosion earthquakes and video records.