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In the 1987-88 Antarctic season two Victoria University Programmes were successfully completed.
The McMurdo Sound sediment studies obtained sea floor sediment samples from eight shore-normal transects in McMurdo Sound and along the southern Victoria Land coast. The transects were designed to sample nearshore sediment and biota to a depth of 100 m. Current measurements were also made at many of the sites to improve our understanding of water circulation patterns and their influence on sediment distribution and deposition.
The Mt Erebus seismic programme repaired the TV camera installed on the volcano's crater rim to continue monitoring the activity of the lava lake. Real time TV data was compared to recordings from the Mt Erebus seismic net to understand the eruption mechanisms of this active volcano.
Sea floor sediment samples were obtained from seven shore-normal transects on the southwestern Ross Sea coast from Blue Glacier to Tripp Bay, plus one transect off Cape Armitage, on Ross Island. The transects were designed to sample "near shore" sea floor sediment and biota to 100 m water depth. Samples were taken with modified Shipek grab. Current measurements were made at most of the 100 m site with an InterOcean S4 electromagnetic current meter.
The distribution of sea floor sediment at these transect locations is influence by:
Current flow is approximately parallel to the southwestern Ross Sea coast and shows reversal of direction within the tidal period. Current speeds up to 25 to 30 cm/sec were measured at Gregory Island and decrease to the south at Blue Glacier where a maximum of 12 cm/sec was measured. At Cape Armitage, current speeds of up to 75 cm/sec were measured, and were accompanied by a marked directional change within the tidal period.
The macro biota from most sites have consistent substrate preference and depth zonations. Red spiny echinoids and small (up to 5 cm high) red-brown algae prefer exposed bedrock and coarse gravel generally to 20 to 30 metres depth. Pectens commonly were recovered in shallow depths less than 30 metres, usually on sandy sediment and occasionally bedrock. Sponges and sponge mat were recovered from depths greater than 50 metres on substrate from gravel to muddy sand.
Surveys of the sea floor of McMurdo Sound and Granite Harbour have shown that sediment texture there is, in broad terms, bathymetrically controlled with mud in the basins, muddy sand on the slopes and sand on the shelves (Barrett et al. 1983). Foraminiferal studies also show some bathymetric control, though in this case the controlling factor is the carbonate compensation depth at 620 m offshore and 230 m in the harbours (Ward et al. 1987). The main purpose of this project is to document the relationship between sediment texture, micro-organisms (diatoms and foraminifera) and water depth from the shoreline to the 100 m contour along the Victoria Land coast. This areally limited zone has come to be of particular interest because studies of the MSSTS-1 drill core (Barrett 1986) show how variations in species diversity and sediment texture may be used to follow sea level changes in cored sequences. Changes to be expected are an increase in mud content and a decrease in mean size seaward due to declining wave power (cf. Jago & Barusseau 1981; Barrett 1986), an increase in species diversity (Webb et al. 1986) and in the case of diatoms an increase in benthic/planktic ratio (Harwood 1986). Data from the modern shoreline are needed for comparison with older shallow marine polar sequences like that cored in MSSTS-1.
This programme involved a five-person party working from the fast ice in the southwestern Ross Sea. Sea floor samples were taken along eight shore-normal transects from Blue Glacier to Tripp Bay and at Cape Armitage (Figure 1). The transects represent a range of coastal types (exposed to embayed) with a variety of substrates, including bedrock, gravel, sand, mud and sponge mat.
We travelled on the fast sea ice by D-3 tractor pulling three Cantago sledges and used a Grizzly toboggan for bathymetry surveys and route finding. The first sledge was set up as a sea ice drilling platform, with hydrographic winch, drill and drill mast, grab, fuel and tools. The second sledge carried the NZ-1 wannigan, which is fitted with bunks, table, desk and small kitchen. This was used as a laboratory for mixing preservative for the sediment samples, as a dry lab for the IBM PC, used for programming and interrogating the S4 current meter, and as a kitchen and working area. The third sledge carried the remaining cargo, such as tents, personal baggage, the Grizzly when not in use, further fuel and miscellaneous cargo. A VUW ski trailer for use with the Grizzly was towed last.
At each of the eight sampling transects, a bathymetric survey was carried out to determine the slope and topography of the sea floor (Figure 2). This was carried out by drilling 4-inch holes in the sea ice and using an echo sounder to measure the water depth by passing the 200 kHz transducer through the hole below the sea ice.
The sampling strategy was designed so that sediment was recovered from similar depths at each transect. The depth zones sampled included a sea ice scoured zone, from 0 to 5-10 m, a possible wave influenced zone, from 5 to 20 m, and a non-wave influenced zone, from 20 to 100 m. The effects of bottom currents, which are depth and site specific, were also considered in the sampling strategy.
The sediment samples were recovered with a modified Shipek grab designed and built at Victoria University. The grab has two interchangeable 180×180 mm hemicylindrical buckets that take a 90 mm deep scoop of the sea floor. These samples were first photographed and described intact, then split into portions and preserved in formalyn. A subsample of each grab will be preserved as an archive specimen, and another split will be used for foraminiferal work and grain size analysis.
Several areas of exposed bedrock were identified during the sampling programme. These sites had very little sediment cover, and are generally in shallow water. They include exposed capes and steeply dipping (17°) sea floor. Tripp Island and Gregory Island exhibit this sort of submarine topography (Figure 2). The bedrock surfaces extend deeper than sea ice influences, so other factors must be responsible for the lack of sediment. These include glacial ice scouring, non-deposition at the present time and strong current activity.
Intermediately sloping sea floor localities include Cape Roberts, Dunlop Island and Cape Bernacchi (Figure 2). These have exposed bedrock from 0 m to 10 or 20 m, then gravel which grades to muddy sand at about 100 m.
Beach-type coastal topography is found at Explorers Cove (New Harbour, Figure 2) and Blue Glacier. These areas have gravelly sand at 0 m with sediment fining into the deeper water. Blue Glacier (0 to 40 m depth) is a moraine remnant, presumably ice cored, with a slope of 15°. Further offshore the slope lessens to 3°.
Cape Armitage, on Ross Island (Figure 2) has a substrate of volcanic scoria. We found this transect to be strongly influenced by sea floor anchor ice formation in water to 11 m depth, and a very strong current (75 cm/sec) regime.
Invertebrate animals and some plant materials were collected during the grab sampling programme. Different species of animals and plants have certain substrate preferences. Echinoids and some pectens were found on the bedrock surfaces (Figure 2). Pectens were also found in shallow water on sandy mud bottoms. Live sponges and sponge mat (disaggregated dead siliceous sponges) were found from 50 to 100 m and probably continue deeper in certain areas off shore (Ward 1984). Large (5 cm high) reddish algae was found only in the northern areas, as isolated specimens, the algae occurred in water less than 50 m deep, on bedrock or coarse sediment. Its distribution could be influenced by proximity to more open water and Ross Sea circulation patterns.
Diatoms, often comprising biogenic mud of an olive-green colour, were present entrapped in sponge mat and in deeper water basins, especially in areas of low current activity, such as Tripp Bay. Specimens of diatom ooze were collected for S216.
Water current measurements were made this season at the 100 m site of most of our coastal transects using a newly purchased InterOcean S4 electromagnetic current meter. This current meter is housed in a 250 mm diameter sphere, has no moving parts, records data internally and is ideal for deployment through our 300 mm diameter access holes in the sea ice. The instrument was programmed and interrogated with an IBM PC operated in the warm environment of the wannigan (NZ-1).
Two modes of deployment were used at the 100 m deep sites. Water column profiling measurements were made while either raising or lowering the current meter with our new hydraulically controlled hydrographic winch. Short term (12-24 hours) fixed-mooring measurements were also made by suspending the current meter on the winch wire 1.5 m ± 0.5 m above the sea floor. The height of the instrument above the sea floor could not be fixed precisely using this method of deployment because of the approximately 1 m tidal rise and fall of the sea ice platform.
Profiles and short term deployments were also made in central Granite Harbour near the MacKay Glacier Tongue and in central New Harbour (S216 Trap Site). This data will be used for planning a longer term deployment (2 months) proposed for the 1988-1989 season.
Examples of results from profiles and stationary moorings are presented in Figures 3 and 4. The highest speed measured along the southwestern Ross Sea coast
Water samples for oxygen and carbon isotope analyses by Dr Enriqueta Barrera, Ohio State University, were taken at the 100 m site of each of the eight transects. Samples were collected using a small Niskin bottle deployed 10 m below the sea ice and 5 m above the sea floor at each site. Subsamples were measured for pH within 2 hours of collection. We had hoped to collect water samples for this study from previous 1981 sea floor sample sites, but the lack of sea ice cover in the central part of McMurdo Sound made this impossible this season.
A spot depth bathymetry survey was begun this season in Tripp Bay in association with Dr Robert Dunbar of Rice University, Texas (S216). The aim of the survey was to compare Tripp Bay with Granite Harbour and identify any deep basins which could be accumulating diatom-rich sediment as in Granite Harbour. We were also interested in this area as a site which is isolated from the influence of McMurdo Sound oceanographic circulation.
The maximum depth recorded this season was 550 m in the area south of Tripp Bay Glacier Tongue (Figure 1). Further measurements are still required to the east and north of the glacier tongue to complete the survey. The New Zealand survey party, K191, surveyed all flagged bathymetric locations so an accurate map of the sea floor in this area can eventually be constructed.
The three main investigators involved in this project, Dr Peter Barrett, Mr Alex Pyne and Dr Barbara Ward, intend to publish this joint study relating the modern near shore sediment, current measurements and foraminiferal diversity along the coast in a periodical such as the NZ Journal of Marine and Freshwater Research.
The purchase and successful deployment of the S4 current meter this season now gives us the ability to quantitatively study water circulation. In the 1988-1989 season we intend to deploy the current meter at the MacKay Glacier Tongue for two months to record bottom current activity to determine whether glacier-generated mud-carrying density currents occur in this polar marine glacial setting.
Sea floor coring in Granite Harbour by Victoria University (Macpherson 1987) and Dunbar (S216) this season indicates that glacially deposited sediment may exist beneath the 1 m thick cover of diatom-rich mud. The glacial sediments were probably deposited during Holocene expansion of the MacKay Glacier, which is fed from the polar plateau. Granite Harbour therefore may contain accessible glacial marine sediments which could record Holocene changes in polar ice volume for this area of Antarctica.
Granite Harbour continues to be an area of interest for polar marine glacial study because it can be logistically supported from McMurdo-Scott Base, yet is sufficiently far away from McMurdo Sound to be a good model for the deep basins along the Ross Sea coast that have been influenced by plateau ice. We suggest that a small summer science base could be established at Cape Roberts to support marine glacial, oceanographic and biological studies in Granite Harbour and this area of the Ross Sea coast. Such a summer base could also be the nucleus of a drilling camp if further offshore drilling were to go ahead near Cape Roberts.
This season we were joined by Lt Fernando Zurita, a guest scientist (geologist) from Ecuador, whose scientific interest was close to our oceanographic studies. He was only able to spend a short time with us in the field before leaving to organise the Ecuador Antarctic Oceanic Cruise beginning in early December. I think Lt Zurita's visit to Scott Base and involvement in our programme was successful because of our compatible scientific interests, but unfortunately his time with us in the field was rather short, and he was not able to observe the full range of our operations.
We wish to thank the University Grants Committee and the VUW Internal Research Committee for financial support. Our thanks also to Antarctic Division, DSIR, for logistic and field support, to OIC, Scott Base and summer support staff, particularly Clayton Ross, summer mechanic, for advice and help while we were in the field.
Special thanks to Geoffrey Blake, our DSIR field assistant, for his enthusiasm and mechanical expertise, and to Lt Fernando Zurita, for his help and cooperation at Scott Base and during the short time he was in the field.
We are grateful for the technical expertise and willing assistance of the Kiwi surveyors, Brian Anderson and Garth Falloon, K191. We also appreciated the assistance and cooperation of S216, from the U.S. programme.
VUW Mechanical Workshop provided practical assistance and expertise with the hydraulic winch, grab and other equipment, and their efforts are greatly appreciated.
TV surveillance of the Erebus lava lake was restored to full operation on 17 November 1987 by replacing the camera box, the window of which had become opaque by etching in volcanic gas. The quality of the pictures was also improved by changing the lens from 16 to 25 mm, and raising the transmitter antenna.
The explosions were weaker than in 1986/7, but the lava lake was larger, and was L-shaped rather than round as before. By 3 January, 108 eruptions had been videotaped at the Scott Base receiving station, and the recordings from the Erebus seismic net had been played back, and later analysed for the 27 eruptions which were seen to eject bombs.
The total TV view time of the crater was 435 hours in 38 days, an average of 11.4±9.2 hours per day, and the average interval between eruptions was 4.03 hours. The eruptions were not randomly distributed, but were clustered in the periods 00-02 and 08-14 hours UT.
As in 1986/7, the TV explosion instant was earlier than the intercept time of P-waves (at zero distance) by 0.69±0.33 second, but the apparent velocity of P was lower, at 1.77±0.42 km/s. This reflects the smaller seismic amplitudes, and consequently later readings of emergent onsets at the more distant stations.
The seismic and infrasonic signals were all of the short period Alpha type, reported by Shibuya in 1984, reflecting the small but increasing area of the lava lake.
Erebus is a unique volcano. It is at higher latitude than any other active volcano above sea level, and is situated in an aseismic intraplate region. At present it has a negligible rate of lava eruption (c. 1 m3 per day) but it has maintained a liquid lava lake in its crater since before 1972. The phonolitic lava has higher silica content (56%) and theoretical viscosity (103 Pas at 1200°C) than any other persistent lava lake, yet it persists in unusually cold conditions at high altitude (3580 m).
Expeditions to the summit have consistently reported an average of several eruptions per day. These are accompanied by explosion earthquakes and as well, more than 100 volcanic earthquakes per day occur in the range ML-2 to +2. The foci are as deep as 15 km, and all the seismologists of the IMESS team (1980-1985) agreed that the foci of explosion earthquakes, identified by accompanying infrasound, extended down to 4 km below the active vent.
The installation of TV monitoring of the lava lake in the 1986/87 season showed that surface explosions of the lava lake were the source of the explosion earthquakes, and suggested that the previously determined focal depths were an artifact of adopting model velocities which were lower than the true velocities in the volcano. Accurate determination of the true velocities is difficult because the onsets are emergent, but the seismic wave-forms of different explosions at the same station are often "identical" (cross correlation coefficients exceeding 0.85), and can be stacked to improve the signal to noise ratio. Volcanological observations around the world are just realising the importance of this, and I co-operated in discovering identical explosion earthquakes by computer search methods at Sakurajima volcano, Japan, in February 1988. The instrumentation at Erebus and recording facilities at Scott Base rival the best volcanological observations in the world.
The principal objectives of research for the 1988/89 season are to make the search for "identical" families of volcano-seismic events more efficient by installing a PC computer based digital seismic event recording system at Scott Base, and by using cross correlation, stack and residual software on all adequately recorded events in a routine manner, assemble enough data for reliable statistics and location of the families.
As well as the normal preparations for field work in mountainous areas (done by Lassky and Ellis), it was essential for Dibble and Ball to check that the Erebus telemetry equipment at Scott Base was in good condition and adjustment. Otherwise, much time could be wasted on the mountain trying to cure faults later found to be at Scott Base. For instance, the poor locking of the time code on the TV picture, which the 1987 Science lab Technician had blamed on the TV transmitter up Erebus, was found to be caused by the BNC connector to the time code generator being left half undone over more than half the year. Also, the time channel to the 14 channel Sony data recorder had been disconnected since no one knows when!
A welcome change from the 1986/87 season was that VXE-6 resumed flying helicopters to the lower hut, thus reducing our dependence on toboggans to get equipment up the mountain. In a last-minute switch, however, they delivered our Grizzly to Fang Glacier, when we had all expected to be air-lifted from Fang acclimatisation camp to the hut. After some difficulty starting it because the switch was stiff, the
Terry Ball tried to cure the faults in the camera which had nearly defeated us in 1986/87, by changing components as described in a manual belatedly supplied by Philips. Unfortunately, the instructions did not apply to our camera, and the original components had to be replaced with the fault uncured. Briefly, if the supply voltage drops momentarily, the camera locks into a stable inoperative mode.
While Terry wrestled with this, Ray Dibble, Steve Lassky and Brian Anderson (surveyor) were shifting the TV transmitter and antenna 70 m closer to Scott Base and adding 0.8 m to the mast so as to improve the ground reflected RF signal, and Susan Ellis was making infrared temperature measurements of the lava lake, and warm ground inside and outside of the craters.
Sunshine and shelter from the wind were important for comfort on the rim, and while Ray, Steve and Brian sweltered, Terry, Susan and their equipment 200 m away got cold, and the infrared measurement became unreliable. A further problem with the TV was that transmissions from the Tait radios near the camera also caused it to lock into inoperative modes, necessitating extra trips back to the summit, opening the camera box, and disconnecting/reconnecting the power. Perhaps it was one too many such actions which weakened the power connection so that it failed on 6 December after we had descended. We were greatly indebted to Bill McIntosh of S081, who found and cured the fault for us.
The type LX06002D infrasonic microphones at EI and CON were replaced by type LX0503A barometric pressure sensors to cure intermittent operation. Over most of the first half of 1987, the microphones operated only in the afternoon, seeming to work only in the sunshine, despite the very wide operating conditions of temperature (to −50°C) and pressure. Ice blocking the pin hole pressure ports was a possible cause, although the microphones had been entirely sealed inside condoms in 1985/86 to prevent this, and also corrosion by volcanic gas. The condoms were still in excellent condition, but the resistance of the strain gauge bridge in the microphones had changed for some reason. No explanation for the intermittent operation could be found, but it appears that the
At E1 we also reinstalled the long period horizontal seismometer provided by NIPR in 1986/87 in a niche in the lava dike, 2 m from the previous site, in order to reduce the tilting which had stopped it operating. The component was again radial to the lava lake.
It was the task of Susan Ellis, the longest staying member of the team, to videotape the Erebus TV as many hours a day as possible, and to fast scan each tape, and re-use those with no useful data. The San-ei visual writing seismic recorder was used to help find eruptions on TV. Susan copied each obvious eruption onto an edited videotape, and at the end of her stay, photographed the TV monitor display of the edited videotape with an NTSC camera and recorder provided by NIPR, to get an NTSC copy for Japan and USA. The original recordings were also kept.
The Erebus seismic network was being recorded as part of the normal work of Scott Base, and as each tape was taken off the Sony Data Recorder, Susan replayed it on a second machine at 100x recording speed into a log amplifier and 4 pen chart recorder to get short index charts of time scale 4 mm per hour of the entire 8 day record. Photocopies of these charts of log seismic amplitude will be sent to Drs Kyle, Kienle, and Kaminuma so that they can choose earthquakes for further analysis, or look at statistics of occurrence. (Normally, staff play tapes back at Scott Base × 10 faster, and record the entire waveforms).
For the well recorded explosion earthquakes, and other earthquakes, Susan made normal seismograms of all useful data channels by playing the tapes at recording speed and the chart recorder at 1 mm/s and 10 mm/s. Initially, there were only 6 channels (limited by discriminators) but after Prof. John Schlue of New Mexico Institute of Mining and Metallurgy had carried out some tests with long period seismometers at Abbotts Peak, he brought back the rack of discriminators which NSF had removed from Scott Base on 7 January 1987, and 8 channels were then recorded.
Susan's final task, before she returned to New Zealand on 8 January was to replace the Sony Data Recorder which had been recording Erebus data for 2 years, with the one used for playback, and to pack up the playback equipment for return to NZ and Japan.
Mr Stan Whitfield, the Science Lab Technician in charge of MEEMS at Scott Base for 1988, is continuing to record one or more videotapes each day until the power to the camera/transmitter switches off in the winter night, and to scan them, and re-use tapes
In New Zealand, Susan read the seismograms of explosion earthquakes to 4 January 1988, and plotted the time distance graphs and TV origin times. She also plotted the infrared temperatures, and compared them with those measured in the 1986/87 season.
The paper on the TV results presented as a poster at IUGG, Vancouver, September 1987 was written up in Japan for publication by the University of Kyoto Disaster Prevention Research Institute, and presented at their Annual Meeting on 3 February. A comparative study of Erebus and Sakurajima results using computer techniques was begun at Sakurajima Volcano Observatory in February 1988. A list of papers published for 1987 is shown in VUWAE publications.
The recognition of families of "identical" earthquakes is a fast developing area in volcanic seismology, because it enables the work of locating earthquake foci to be reduced and/or made more accurate. It is easy to do using digital seismograms, and then the stacked average seismogram with improved signal to noise ratio, and the residual waveform showing how individuals differ from average are easily obtainable.
Already an important difference between Erebus and Sakurajima has been found: Erebus explosion earthquakes are often identical from onset to coda, but Sakurajima ones become different in the coda, presumably because the source volumes of the explosions develop differently, even though they may initiate in the same place, and thus cause earthquakes with identical onsets.
In regard to the MEEMS project, NZARP coped very well with the special time limitations, transport problems to and on Erebus, and co-operation with NSF season. The political problems of 3 way co-operation between RDRC, NSF, and NIPR are not yet resolved, and seem to revolve around the US requests for equitable opportunities for trade and scientific exchange with Japan.
Although the different financing and accounting procedures in those two countries make accurate comparison difficult, I believe that the Japanese investment in IMESS equalled that of USA, and that as Drs. Kienle, Kyle and Dibble spent a total of 7 months
The major problem of co-operation in IMESS was the delay in distributing data due to the intensive work of playback, and the time advantage that the institution doing the playback enjoyed. My good relationships with all the parties involved have survived the problem, and I am hopeful that our continued co-operation on a scientist to scientist basis will help reduce the present international and institutional problems.
There was not a single person who was less than helpful in avoiding delays and crises with the 1987/88 programme, but special mention must be made of Jim Barker, Garth Varcoe, Cass Roper, the OIC and Base Mechanic of Scott Base, and VXE6 Helicopter Squadron for giving us the priority and good will needed to make my extremely tight timetable for Erebus and the Sakurajima Volcano Observatory possible. I assure them all that it was very worthwhile.
I also thank my team of Susan Ellis, Terry Ball and Steven Lassky for their dedication, Brian Anderson, and Bill McIntosh for assistance on the mountain, Phil Kyle for co-operating in our descent from Erebus, and for supporting the continuation of the seismic programme with NSF, and Katsu Kaminuma for his full and generous support of the programme, even though he did not get permission to come to Scott Base this season.
Surveys of the sea floor of McMurdo Sound and Granite Harbour have shown that sediment texture there is, in broad terms, bathymetrically controlled, with mud in the basins, muddy sand on the slopes and sand on the shelves. The main purpose of this project is to document the relationship between sediment texture, micro-organisms (diatoms and foraminifera) and water depth from the shoreline to the 100 m contour along the Victoria Land coast.
Sea floor sediment samples were obtained from seven shore-normal transects from Blue Glacier to Tripp Bay, plus one transect off Cape Armitage, on Ross Island. Current measurements were made at most of the 100 m sites with an TnterOcean S4 electromagnetic current meter.
The programme involved a five-person party working from the fast ice in the southwestern Ross Sea, Sea floor samples taken with a modified Shipek grab along the eight transects sampled diverse substrates and biota. The areas sampled represent a range of coastal types (exposed to embayed) with a variety of substrates, including bedrock, gravel, sand, mud and sponge mat.
This event used several large equipment items from Scott Base which required checking and minor repair-cleaning before use. Our field assistant Geoff Blake went to Scott Base early to prepare some of this equipment and our scientific equipment. It was a little disappointing however to find more items than I expected required servicing before we could use them. This servicing should have been the responsibility of Scott Base staff. The main problems were the Cantago sledges which required digging out of the snow and servicing, NZ-1 wannigan which we had to clean twice because it was used for Scott Base Sunday excursions after we had taken possession, and the D3 servicing which is the Scott Base mechanic's responsibility, although some people thought this was our job also. There was also some confusion over generator allocation and other mechanical items which are serviced by the mechanic but controlled by the storeman. A solution to this type of problem would be for the mechanic to have both servicing and issue responsibility for this equipment. An example of this problem was that our field assistant ended up servicing two generators, one for our use and one that was allocated to another field party.
We travelled on the fast sea ice by D3B LGP tractor pulling three 5 ton Cantago sledges and used a Grizzly toboggan (G4) for bathymetry surveys and route finding. The first sledge was set up as a sea ice drilling platform, with hydrographic winch, drill and drill mast, grab, fuel and tools. The second sledge carried the NZ-1 wannigan, which is fitted with bunks, table, desk and small kitchen. This was used as a laboratory for mixing preservative for the sediment samples, as a dry lab for the IBM PC, used for programming and interrogating the S4 current meter, and as a kitchen and working area. The third sledge carried the remaining cargo, such as tents, personal baggage, the Grizzly when not in use, further fuel and miscellaneous cargo. A VUW ski trailer for use with the Grizzly was towed last.
The towed load for the D3 was quite high as indicated by the necessity to remain in 2nd gear on soft dry-cold snow in the area from Ross Island to the McMurdo Ice Shelf. We estimate that each Cantago sledge with cargo had a dead weight of about 5 ton giving a total dead weight of 15 ton. There was no method available to measure draw bar pull directly, however, this was estimated from published D3 performance curves to be about 8000 lbs (35 kN) on soft snow in 2nd gear, reducing to about 3000 lbs (15 kN) in 3rd gear on thin snow-smooth sea ice. This would seem to be a sensible maximum load for long distance travel when a variety of surface conditions are encountered. The D3 performed very satisfactorily with only a few minor problems. The ether cold start facility was required at temperatures below −5°C and the batteries require heating below −15° to −12°C. A Herman Nelson heater should be considered a necessary accessory for the D3 when in the field, especially in the October-November period. A field rescue kit consisting of 2 heavy duty snatch blocks, chain and materials to make a deadman anchor should also accompany any bulldozer while in the field. This was not required by us this season but recent experience has highlighted the advantage of such equipment.
We had minor problems with clogging of the primary fuel filter which is in a different priming pump configuration than shown in the operator's manual. Perhaps a manually operated priming pump should be used in Antarctic conditions. There was also a leaky engine seal which required regular additions of oil. The loss of oil however decreased as the atmospheric temperature increased and as the engine accumulated more operating hours. The winch-wind wire became damaged while extracting the D5 on 1 November. This problem reoccurred in New Harbour and required cutting the winch wire and enlarging pan of the gap between winch drum and cheek to remove the crushed
A running log for the D3 is shown in table 1 with an analysis of fuel consumption for varying conditions.
Several of the older ski shells on these sledges require replacement as the keels have been worn through. The draw bars and rear ski connecting bar should also be raised to give better ground clearance, as on the newer sledges and USARP sledges.
The wannigan proved to be very useful for our laboratory, kitchen and eating area and is well fitted out. The following improvements are suggested to increase the NZ-1 versatility.
This toboggan was used generally for short distances (bathymetry and route finding) and travelled for much of the time on the third Cantago sledge to keep the distance travelled to a minimum. The machine performed satisfactorily with adjustments required to the chain drive gear box and twin carburettor, which are more difficult to tune than the standard engine.
Four hours helo time was used for a sea ice reconnaissance to Tripp Bay. The route expected to be taken by the D3 was flown to make a map of ice conditions. Two ice crack monitoring stations at Depot Island and C. Roberts were also established during this flight. The helo reconnaissance proved to be extremely valuable and the route map used extensively. We recommend that similar flights should be made for future tractor trains.
The improvements made in field rations are commendable. The availability of packets of frozen vegetables, roasts, chops and bacon was most appreciated. Comments on quantities, etc. were made on the form filled out for the field Store Person before leaving Scott Base.
We do feel the organisation of the food boxes could be standardised further. The food boxes should include staples, such as flour (not just self-rising), toilet rolls and paper towels. The only items to be obtained separately should be perishables, such as cheese, salami, frozen meat and vegetables.
A new "Fin" 4" diameter hand operated ice auger was used extensively by K042 this season. It is a fast efficient way of drilling holes to test ice thickness and therefore especially useful for the D3 operation. The drill was also used for bathymetry surveys to make a hole for the echo sounder transducer. The drill should be available for future tractor trains; however, some care and skill is required for efficient operation. Good quality files, sharpening stone and adequate instruction is necessary to keep the drill razor sharp and operating properly.
Three large red survival boxes were carried by the tractor train and were deployed at Butter Pt Hut, Cape Roberts Hut and on the south side of Blue Glacier for helo lift to C. Chocolate. In addition, old food caches were returned to Scott Base from the C. Roberts trig site and Butter Pt. huts. A food cache in old NZARP 20 man day cardboard
A small dismantled hut (toilet) was carried by the tractor train to Spike Cape where it was offloaded for K121 and later helo-lifted to Hanson Ridge. This could have been better organised at Scott Base, as we understand no fasteners were supplied to erect the hut. Two empty 44 gal fuel drums were also supplied by K042 with tops removed by plastic explosives, for anchoring the hut on Hanson Ridge.
A Codan SSB installed in NZ-1 and 2 Tait VHF radios were used this season. This combination of radio systems was generally very satisfying with the VHF radios giving us flexibility for surveying and route finding. Some minor problems were noted and these are listed below for future consideration.
On 2 or 3 occasions we travelled late into the night and could not contact Scott Base after stopping between 0100-0300 hours. We had understood Scott Base was operating a 24 hour radio watch and we felt unfairly criticised when we did not respond to the 0800 hours schedule. There seemed to be some breakdown in communication between the radio operators' and field operators' organisation at Scott Base.
The area around the C. Roberts hut was cleared of redundant equipment stored during previous VUWAE-K042 visits in 1982-1984. All this equipment was returned to Scott Base for disposal or return to NZ.
Explosives remaining at Butter Pt. from the CIROS programme were destroyed as per request from Ant. Div. Building and Services Officer. A small quantity of explosives was returned to the NZARP magazine after this season's field programme.
A 44 gal. drum incinerator was made in the field to burn flammable and metal wastes on the sea ice. The incinerator in conjunction with some fuel gave a clean smokeless burn which reduced to non-burnable materials which were returned in the drum to Scott Base for disposal. Human and biodegradable waste were released into the sea.
Analysis of running log gives the following indications of performance for different conditions lowing near maximum suggested load.
In exception conditions on warm (wet) sea ice the D3 and sledges were measures travelling at 12-14 km per hour with the ASV speedo. For general planning in good surface conditions we suggest using an expected fuel consumption of 12% per hour:3.5% per km and speed between 5-7 km per hour.
To study the mechanism of the strombolian eruptions from the lava lake, as it reforms after disappearing in the 1984 activity, by a combination of TV surveillance, seismic infrasonic, and infrared monitoring of the eruptions. The study is made jointly by Victoria University of Wellington and the National Institute of Polar Research, Tokyo, and in close cooperation with New Mexico Institute of Mining and Technology. They are studying the release of volcanic gases from the lava lake, both during and between eruptions, by means of a correlation spectrometer, and by collecting samples of aerosols, sublimated salts, and newly ejected lava bombs.
The MEEMS project makes use of the old IMESS seismic array by unofficial courtesy of NSF. The infrasonic sensors, and the long period horizontal seismometer connected to the array at E1 and CON belong to VUW and NIPR respectively. The recording equipment at Scott Base belongs to NIPR, and the telemetry receiving equipment belongs to NSF, except for one bank of discriminators, which belongs to VUW. All the TV monitoring equipment belongs to VUW. Seismic recording materials are provided by NIPR, and videotapes are provided by VUW.
The year's work from the date K044 arrives, comprises servicing the Scott Base installation, and then the Erebus installations while observing the changes in crater temperature, activity and morphology. Ideally, all seismic tapes recorded since Winfly should be played back on to paper charts at Scott Base for distribution to NIPR, VUW, NMIMT, and GIUA. This enables analysis to begin promptly on data collected under our control. Priority is given to eruptions for which both TV and seismic data are available. If this is not done before the seismic tapes and playback machine are returned to Japan, the analysis will be delayed for about 8 months, and equipment faults may persist.
The planning phase was complicated by the initial belief by the Program Manager that the problems of international cooperation would force cancellation of the program. Accordingly, I accepted a 3 month fellowship in Japan from December 1987 through February 1988. Further, I was committed to attend the IUGG General Assembly in Vancouver, which clashed with the Tekapo Training Week. To the credit of all concerned, the Antarctic field programme did not suffer, and if anything, the personal relationships and understanding of the problems were improved all round. However, I remain convinced that regular attendance at Tekapo, and the event briefing session is essential in normal circumstances.
My cargo going South was no problem. It consisted of one large cargon (500 kg) of NZ and Japanese equipment and 150 lb hand carry (see Appendix 1 for detail). Susan Ellis had a problem coming north, because she had to bring all the recordings as hand carry luggage. She was relieved to be met at Christchurch, and given some help.
Cargo between NZ and Japan proved a problem, because there were no Japanese participants to smooth the way through Customs. Prof Kaminuma had difficulty clearing the seismic tape recordings when they arrived in Japan, even though he purchased and shipped them from Japan. His solution is to always use "Kaminuma and Dibble" as both consignor and consignee, to ensure that one of us is present at each end, but he was confused when tapes (used) I sent him arrived soon after he had sent new ones south, and thought his had done a round trip!
Grizzly No.5 was in good order, and already tuned for high altitude when we received it. We had hoped to learn riding skills on the easy slopes at Fang, and be able to drive up Erebus, and so avoid helicopter delays, but the decision was to fly the Grizzly direct to the hut. The helo pilot declined, and delivered it to Fang when he came to lift us to the hut. So at short notice, we tried to drive it up. It wouldn't start (frozen switch), and we had to go up by helo as planned, and then Steve and Brian walked down to try again, and easily rode it up. The Grizzly proved equal to the NSF Bombadier, except it was harder to turn.
About half a tank of fuel was used per day. The windscreen broke in half when I was trying to secure it while the helo was waiting to take us up to the hut on 12/11/87.
Our put in was combined with K191, and took 3 lifts to Fang on 9/11/87.
I Our lift to the Hut was delayed 1 day by weather. On 12/11/87, 2 cargo trips from S.B. to hut, and then 1 to Fang with the Grizzly, and 2 from Fang to Hut were made. The last of these medivae'ed Garth to Scott Base with a viral infection.
K191 returned to S.B. in 1 flight on 16/11/87. K044 returned in 2 nights, 1 from Fang with the Grizzly, and 1 from the hut.
The initial lift on 9/11/87 was free, and the return from Fang was a backload on S081's put in.
Mr Steve Lassky will include our weather in his report.
No significant accidents occurred, but people using toboggans on difficult terrain should get practise before their put in.
The Dome tents again proved excellent on the Erebus Plateau.
Chocolate biscuits and instant noodles should be a standard item in ration boxes.
Our troubles starting the generator and Grizzly made us wish for better instructions in the Field Manual, particularly about the complexity of the Grizzly starter switch. Perhaps more comprehensive field manuals should be supplied with these equipment items.
The Tait VHF handheld radios were again outstanding for communicating with "Scott Base" and with the Science Lab itself, via the repeater station. Battery charging by the solar panels was excellent. The small PEL sets on 5400 kHz were again useless at Fang Glacier, which is within the skip distance, and in the shadow of Erebus.
The general efficiency of Scott Base radio skeds was excellent, which helped the smooth running of the field program this year.
We made considerable use of the Scott Base Science lab, and were very grateful to Paul Purvis of Telecom, who helped out after the technician assigned to MEEMS
Necessary additions to the lab equipment include:
Better designation of storage areas for spares, and recording materials and box files for service manuals and instructions would help the lab technicians.
The two NSF huts on Erebus were in good condition, and contain adequate food, cooking equipment (white spirit) and furniture. Both have some bedding inside, and a survival box outside. Also fire extinguishers and oxygen bottles, but those in the upper hut are of uncertain condition. Both sites are tidy.
All garbage and sewerage was retroed to McMurdo by helo.
During the period of 16th December 1986 to 7th January 1987, 65 eruptions of Mt Erebus, Antarctica were recorded on videotape by a television camera mounted on the crater rim. The associated earthquakes were recorded on a net of nine seismometers and two infrasonic microphones. Timing on seismic and video records enabled reading to 0.04 s but due to their emergent nature, onset times were rarely this accurate. Plotting seismic arrival times from stacked eruptions against distance from the crater showed the seismic intercept time to be 1.48±0.05 s later than the time of visible explosion, and gave a surprisingly high apparent seismic velocity of 4.0±0.1 km/s. These values suggest that the source of the seismic waves is the visible explosion rather than that the seismic waves trigger the explosion. 60 of the recorded eruptions occurred in and around the lava lake, throwing out bombs and being accompanied by earthquakes. The other five took the form of ash jets, from vents near the lava lake, and were weakly seismic or aseismic. Time in night measurements for bombs gave ejection velocities ranging from 5 to 75 m/s and a maximum thrown height of 300 m above the lava lake.
Granite Harbour (77° south) is a glacially scoured embayment twenty kilometres across and up to 900 metres deep on the Victoria Land coast of Antarctica. Most of the ice entering the harbour comes from the Mackay Glacier, a 500 metre thick outlet glacier from the East Antarctic Ice Sheet. The Mackay is largely wet-based, flowing at a rate of 214 m yr−1, and terminates as a floating ice tongue more than four kilometres long. Granite Harbour is of normal marine salinity as it receives virtually no input from meltwater streams, and as it is ice covered and microtidal, currents and waves have little influence on sediments.
Sediment entering and being deposited within the Harbour was sampled during the austral summers of 1983 to 1985, and rates of transport and deposition determined. More than 60 textural analyses from 18 shallow penetration gravity cores show that the sea floor sediment is dominantly sandy mud with a few scattered clasts. The sea floor sediment is divided into seven lithofacies which correspond to divisions of glacial marine sedimentation made by Anderson et al.
−1 of sediment enters the Harbour as basal debris, but melts out beneath the Mackay Tongue within one to two kilometres of the grounding line. Textural studies indicate that about one third of the basal sediment is carried into the deeper parts of the Harbour, probably by lateral advection, in low velocity bottom-hugging currents from beneath the Mackay Glacier Tongue. The remainder is inferred to form a prograding wedge of sediment seaward of the grounding line. Lateral advection is also inferred for transporting up to 45 000 tonnes yr−1 of biogenic-rich mud from shallow areas or from outside the Harbour and depositing it within the harbour basins. Less important processes that introduce quantifiable amounts of sediment are the deposition by dominantly katabatic winds of about 1 810 tonnes yr of coarse silt/fine sand onto the Mackay Glacier surface and the sea ice, and the settling from free suspension in the water column of about 340 tonnes yr−1 of biogenic rich debris.
Sediment accumulation rates have been determined using the decay profiles of unsupported 210Pb within two sea floor cores from the deep areas of Granite Harbour. The rate has averaged 2.48 mm yr−1 over the past 100 years. This rate is used to provide an estimate of sediment deposition of 150 000 tonnes yr−1 for the area of the Harbour deeper than 400 m (about 50%).
Ice-rafted detritus is present within sea floor sediments from the Harbour, but most have characteristics associated with supraglacial debris. An implication of this observation is that coarse debris, within the recent veneer of Antarctic continental shelf sediment, probably represent ice-rafted supraglacial debris, which is likely to be more abundant during interglacial rather than glacial periods.