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Victoria University Antarctic Research Expedition Science and Logistics Reports 1974-75: VUWAE 19

SCIENTIFIC ACHIEVEMENTS

page 9

SCIENTIFIC ACHIEVEMENTS

Erebus expedition (McMurdo Volcanics project)

  1. The geology at the northern end of Black Island was examined and no large differences from early reports were found. A drill site for the Dry Valley Drilling Project was located and recommended to officials of the project. No hole was drilled however.
  2. The activity pattern of Mt. Erebus was observed and can be compared to observations made in November 1973 by Kyle and in 1972/73 by Keys, Kyle and others.

    Mt. Erebus contains a permanent convecting lava lake of anorthoclase phonolite (kenyte) composition. The lake has expanded in size since 1973. Only 3 permanent lava lakes exist in the world. The others are in Ethiopia and Zaire (and because of political situations in those countries are inaccessible to volcanologists). Erebus is unique in being the only phonolite lava lake, the others are basaltic.

    Although the lava lake could not be sampled because of dangerous eruptions in the inner crater, bombs were frequently thrown out on to the main crater floor and crater rim and could be sampled. The only difference between such material and lava collected from the lava lake is probably the loss of volatile gases such as F, S, and Cl from the bombs.

    Lambert (N.Z. Press Association) and Kyle witnessed an eruption from the inner crater rim. This was the smaller of 2 eruptions recorded on the Scott Base seismograph net. A vent on the south-eastern quadrant (named the active vent) of the inner crater filled rapidly (less than 10 to 15 seconds) with lava. As the lava was about to flow over the rim of the 15 to 20 metre wide vent it exploded violently, - "like a battery of 25 pounders" to quote Lambert. Lambert and Kyle were 150 m away directly in line with the vent, and were thrown to the ground. As they ran for shelter several large bombs were seen flying through the air at close quarters. Keys also witnessed two large eruptions both of which originated in the active vent, and threw molten material more than 300 m above the inner crater floor.

  3. The geology around the flanks of the active cone of Mt. Erebus was examined.

Erebus expedition (Seismic studies)

  1. Three slow motion type seismographs (Dibble, 1964) and an ink chart recorder of seismic power (Dibble, 1969) were used to record at 5 sites: 3 surrounding the main crater at a radius of 1 km; one in the ice cave near the camp at 0.5 km radius; and one near the main crater centre. Twentysix [sic] days of recording were obtained between December 3 and 31, including 12 days with simultaneous recording at all 5 sites.
  2. No volcanic tremor was recorded, but an average of 1000 volcanic page 10 earthquakes per day in a range of 0.1 to 106J were recorded. The parameter "b" (Richter, 1958) for a sample of 1000 earthquakes had the value of 1.2.
  3. In a total of 24 hours of documented visual observations of the inner crater, all earthquakes of 103J or more were explosion earthquakes corresponding with explosions of either the main vent or the lava lake. Some smaller earthquakes were accompanied by eruptions, but those accompanying the bursting of large bubbles in the lava lake were too small to be recorded. However most earthquakes were B-type volcanic earthquakes (Minakami, 1963) not accompanied by audio-visual activity, but otherwise similar to explosion earthquakes.
  4. It was not possible to predict safe periods for the descent into the inner crater from the seismic recordings, and as yet, the type and location of the explosions and eruptions cannot be recognised from the seismograms because they are all different. However the general level of activity over long periods could undoubtedly be followed by means of a radio telemetry seismograph at the southernmost of the 5 sites, recording at Scott Base. This would aid the planning of future expeditions to the volcano.

References:

Dibble, R.R., 1964: A Portable Slow-motion Tape Recorder for Geophysical Purposes. N.Z.J. Geol. Geophys. 7(3), 445-65.

Dibble, R.R., 1969: Seismic Power Recordings during Hydrothermal Eruptions from Ruapehu Crater Lake in April 1968. J. Geophys. Res., 74: 6545-51.

Minakami, T., 1963: A Note on Earthquakes originating from Volcanoes. From Geophys. papers dedicated to Prof. Kenzo Sassa, Kyoto Univ. Geophys. Inst.: 277-83.

Richter, C.F., 1958: "Elementary Seismology". Freeman, San Francisco, 1-768.

Glacial Sediment Studies

  1. The discovery of two layers of ground moraine separated by river gravels at 1800 m on Table Mountain indicates two distinct periods of temperate glaciation separated by a warm period. Previously only one such glaciation prior to 5 million years ago had been postulated to account for the scattered high level moraines in the Transantarctic Mountains (Mayewski, 1973).
  2. sea water was discovered in a rift on the Crazy Ice Rise near the head of the Ross Ice Shelf. The rift, about 15 m deep and 2 m wide, has a floor of ice 10 cm thick, which can easily be broken. The water beneath is salty, and has the same freezing point and salinity as normal sea water. In addition, red-brown filamentous algae were collected. The rift is 500 km south of the southern margin of the Ross Sea, and has given access to the world's most southerly sea water. Samples collected will provide valuable data on the nature of the sea beneath the ice shelf. This is the first page 11 time that the sea beneath the Ross Ice Shelf has been sampled, and the results (Barrett, in preparation) will be of great value and interest to oceanographers and marine biologists.
  3. About 120 samples were taken from cores drilled by the Dry valley Drilling Project (Holes 10, 11, 12) and a further 100 were taken from around Table Mountain, Taylor Glacier and New Harbour for comparative study. These will require months of work to analyse and interpret, and are being worked up as an M.Sc. thesis (Powell, in preparation).

References:

Barrett, P.J. In preparation. Natural access to the sea beneath the Ross Ice Shelf at Crary Ice Rise, Antarctica.

Mayewski, P. 1973. Glacial geology and Late Cenozoic history of the Transantarctic Mountains, Antarctica. Ph.D. Thesis, Ohio State Univ., Columbus, Ohio, 215 pp.

Powell, E. In preparation. Textural characteristics of some glacial sediments in Taylor Valley, Antarctica.

Seismic profiling in the Western Ross Sea

  1. The main objective of the Ross Oceanographic Seismic Survey was to collect further information (Northey & Sissons, 1974) on the structure and thickness of sediment in McMurdo Sound.

    The results serve the dual purpose of indicating the best sites for the Dry Valley Drilling Project to drill, as well as providing a means of tracing stratigraphic horizons away from the drill sites using the seismic reflection profiles. Seismic velocities in the top sedimentary layers can be found from the refraction results.

  2. Good profiling weather (low wind speeds, open sea water further west and south than usual) and few major equipment faults allowed us to carry out a very thorough profiling programme both in Terra Nova Bay and McMurdo Sound; a contributing factor to the almost continuous profiling was having two independent but parallel sets of equipment which could be interfaced at any stage.
  3. Preliminary investigation of the results in Terra Nova Bay appear to show two major glaciations to have shaved the sediment cover off to about 450 m and 650 m below present sea level, possibly caused by extended grounding of the Ross Ice shelf. There was later deposition of over 300 m of glacial moraine in places. An unusually deep area was found in Terra Nova Bay (1300 m); total sediment thickness here exceeds 1 km.
  4. In McMurdo Sound there are many infilled valleys with sediment thicknesses up to 500 m. These layers are seen to dip at between 1/2° and 2° to the west in the northern part of the Sound, whereas in the southern part acoustic bedrock (basalt?) has little sedimentary cover and a rugged topography. Hence on first appraisal it seems that better results from drilling would be obtained as far north as winter ice conditions permit.
page 12

Reference:

Northey, D.J. and Sissons, B.A. 1974. Preliminary Seismic Profiling Survey in McMurdo Sound. DVDP Bulletin No. 3, p. 234-9.

Late Cenozoic Stratigraphy

  1. The "silty till deposits" - the bedded polymictons (Murrell, 1973) - throughout the Taylor Dry Valley were described and sampled in detail. At 10 measured sections (max. 30 m thickness) in the valley, rather similar fine sediments and inclusions, interbedded with coarse sands, pebbly sands and very coarse unsorted material (till) are recognised below 300 m elevation. These sediments are considered as having their origin within a fiord and in a similar manner (but probably younger.) to those named as basal silts (Prospect Till) in Upper Wright Valley (Vucetich and Topping, 1972). The DVDP Commonwealth hole showed that, as predicted (Murrell, 1973) the bedded polymicton and till sediments were appreciably thick - in fact some 300 metres.
  2. A minimum age for the formation of the Taylor "fiord" may be determined from radiometric ages of the few tuff beds recognised, and also from secondarily transported basalt scoria.
  3. In the Lake Vida area the Victoria Drift and Insel Drift (Calkin, 1964) were examined over a wide area for comparison with the established basal silt till of Wright Valley (Vucetich and Topping, 1972). Natural outcrops were found to be limited. However a probable fine-grained tuff bed was sampled.

References:

Calkin, P.E. 1964. Geomorphology and glaciology of the Victoria Valley, southern Victoria Land, Antarctica. Ohio University, Institute of Polar Studies, Report 10, 66p.

Murrell, B. 1973. Cenozoic stratigraphy in Lower Taylor Valley, Antarctica. N.Z.J. Geol. Geophys. 16(2), 225-42.

Vucetich, C.G. and Topping, W.W. 1972. A Fiord Origin for the Pecten deposits, Wright Valley, Antarctica. N.Z.J. Geol. Geophys. 15(4), 660-73.

Basal Beacon Studies

  1. Twenty-one stratigraphic sections/were measured between the Royal Society and Olympus Ranges. Detailed sampling for mechanical and chemical analysis was performed at each locality.

    An important section at New Mountain was measured to near the top of the Beacon Heights Orthoquartzite.

  2. Nearly 600 paleocurrent measurements were taken on appropriate structures within the New Mountain Sandstone. Detailed statistical analysis of this data will show any lateral and vertical changes in transport direction within the New Mountain Sandstone.page 13
  3. Detailed sampling of the Terra Cotta Siltstone Member was performed. It will now be possible to carry out detailed major and trace element chemistry of the red- and green-colour and Terra Cotta Siltstone.
  4. The stratigraphic position of the Boreas Subgreywacke Member was established at Plane Table in the Asgard Range. It was also established that the unit does not represent a tillite.
  5. A previously unknown basement contact on Mt. Jason was observed. This extends the known areal distribution of the Windy Gully Sandstone and the Terra Cotta Siltstone northward to the Olympus Range.
  6. Preliminary detailed work was carried on the Altar Mountain Formation. A section was measured and samples taken from four localities.
  7. The Heimdall Erosion Surface was observed on Table Mountain where it had not been previously noted.
  8. Evidence for major rafting by dolerite sills was found at New Mountain. Previously the sill was thought to split the Terra Cotta Siltstone. It was established that in fact the whole of New Mountain has been rafted 3 km to the west by the peneplain sill.
  9. Samples of basement granites were taken for radiometric dating. Samples were taken from the basement contact at New Mountain, Mount JJ Thompson in the Taylor Valley and Mount Odin in the Wright Valley.

Salt Project

Salt and soil samples were collected at Mt. Kempe, Table Mountain, Knobhead, Lake Bonney, Black Island, Mt. Erebus summit plateau and crater area and the Fang.

Knowledge of salt distribution can now be extended to these areas not previously sampled.

2.Soil temperature and moisture profiles were measured in many different localities in these areas and correlations made with other site parameters. These data are necessary to extend to soils the study of salt migration and distribution processes investigated previously (Keys et al., 1975).
3.Systematic sampling on and about mudflows and flooding experiments, all on Black Island, may produce a semiquantitative estimate of the rate of salt movement to the surface in this particular location. Possibly further correlations will be made between the rate of salt accumulation and recent glacial history following investigations on the series of moraines documented by Vella (1969).
4.The coloured and black zones and layers in glacier ice, sampled in previous years (Crump et al., 1974) were investigated at the Fang, at Knobhead on the Ferrar Glacier, and on the Kempe Glacier. At page 14 the latter location the layers appeared to be composed of fine basalt scoria.
5.A Study of the salts and sublimates of Mt. Erebus, commenced in 1972/73, was completed around the summit plateau area. Salts and sublimates were sampled more extensively inside the main crater and at two places on the inner crater wall. Warm ground temperature profiles were measured at several locations both inside and outside the main crater. High temperature sublimates were not obtained, the highest temperature measured being only 79.6°c. This temperature is 0.9°C lower than that of the same fumarole in early January 1973 (Lyon et al., 1974).

References:

Crump, J., Keys, J., Kyle, P., Kyle, R., Luckman, P., McPherson, J., Plume, R., and Rowe, G., 1974. Immediate Report of VUWAE 18, 1973/74. 28 pp.

Keys, J.R., Johnston, J.H., and Freeman, A.G., 1975. Salt Distribution Processes affecting Salt Movement in South Victoria Land, Antarctica. Part 1. Salt Movement down slopes in the Taylor Dry Valley. (Submitted to N.Z.J. Geol. Geophys.).

Lyon, G.L. and Giggenbach, W.F., 1974. Geothermal Activity in Victoria Land, Antarctica. N.Z.J. Geol. Geophys. 17(3), 511-21.