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Volcanic Activity and Seismicity of Mount Erebus, 1986-1994 RAYMOND R

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Volcanic Activity and Seismicity of Mount Erebus, 1986-1994 RAYMOND R absence of Pliocene and Pleistocene diatoms beneath most change. Part 2 (Antarctic Research Series, Vol. 60). Washington, of the Ross embayment. The model is consistent with avail- D.C.: American Geophysical Union. able stratigraphic, sedimentologic, and geomorphic data Drewry, D.J. 1983. Antarctica: Glaciological and geophysical folio. Cambridge, U.K.: Scott Polar Research Institute, University of from the Ross embayment. Despite the paucity of data, the Cambridge. cross-section presents a hypothesis regarding the stratigra- Engelhardt, H., N. Humphrey, B. Kamb, and M. Fahnstock, 1990. phy that may be preserved in the Ross embayment, including Physical conditions at the base of a fast moving ice stream. Sci- the Bentley Trough. The model can (and, I hope will) be ence, 248(4951), 57-59. tested in the coming decade(s?). Testing this model will Harwood, D.M., R.P. Scherer, and P-N. Webb. 1989. Multiple Miocene marine productivity events in West Antarctica as recorded in require additional sub-ice sampling in the deep interior Upper Miocene sediments beneath the Ross Ice Shelf (Site J-9). basins and the development of stratigraphic drilling beneath Marine Micropaleontology, 15, 91-115. thick glacial ice. Hayes, D.E., and L.A. Frakes. 1975. General synthesis: Deep Sea This research was supported by National Science Foun- Drilling Project 28. In D.E. Hayes and L.A. Frakes (Eds.), Initial dation grants OPP 92-20413 and OPP 94-96169. results of the Deep Sea Drilling Project. Washington, D.C.: U.S. Government Printing Office. Kellogg, D.E., and T.B. Kellogg. 1986. Diatom biostratigraphy of sedi- References ment cores beneath the Ross Ice Shelf. Micropaleontology, 32(1), 74-79. Alley, R.B., D.D. Blankenship, S.T. Rooney, and C.R. Bentley. 1989. Rooney, S., D.D. Blankenship, R.B. Alley, and C.R. Bentley. 1991. Seis- Sedimentation beneath ice shelves: The view from ice stream B. mic profiling of a sediment filled graben beneath ice stream B, Marine Geology, 85, 101-120. Antarctica, In M. Thompson, J. Crame, and J. Thompson (Eds.), Anderson, J.B., and L.R. Bartek. 1992. Cenozoic glacial history of the Geological evolution of Antarctica. Cambridge, U.K.: Cambridge Ross Sea revealed by intermediate resolution seismic reflection University Press. data combined with drill site information. In: J.P. Kennett and Savage, M.L., and P.F. Ciesielski. 1983. A revised history of glacial sed- D.A. Warnke (Eds.) The antarctic paleoenvironment: A perspective imentation in the Ross Sea region, In R.L. Oliver, P.R. James, and on global change. Part 1 (Antarctic Research Series, Vol. 56). Wash- J.B. Jago (Eds.), Antarctic earth science. Cambridge, U.K.: Cam- ington, D.C.: American Geophysical Union. bridge University Press. Barrett, P.J., (Ed.). 1989. Antarctic Cenozoic history from the CIROS-1 Scherer, R. 1991. Quaternary and Tertiary microfossils from beneath drillhole, McMurdo Sound. Department of Scientific and Indus- ice stream B: Evidence for a dynamic west antarctic ice sheet his- trial Research Bulletin, New Zealand, 245, 1-254. tory. Palaeogeography, Palaeoclimatology, and Pa laeoecology Barrett, P.J., and B.C. McKelvey (Eds.). 1986. Stratigraphy and Antarc- (Global Planetary Change Section), 90, 395-412. tic Cenozoic history from the MSSTS-1 drillhole, McMurdo Sound. Scherer, R. 1992. Diatom paleoproductivity and sediment transport in Department of Scientific and Industrial Research Bulletin, New west antarctic basins and the Neogene history of the west antarc- Zealand, 237,9-51. tic ice sheet. (Ph.D. Dissertation, Ohio State University, Colum- Bentley, C., and J. Clough. 1972. Antarctic subglacial structure from bus, Ohio.) seismic refraction measurements. In R.J. Adie (Ed.), Antarctic geol- Scherer, R.P. 1993. There is direct evidnce for Pleistocene collapse of ogy and geophysics. Oslo: Universitetsforlaget. the west antarctic ice sheet. Journal of Glaciology, 39(133), Bindschadler, R.A., B. Koci, and A. Iken. 1988. Drilling on Crary Ice 716-722. Rise, Antarctica. Antarctic Journal of the U.S., 23(5), 60-62. Scherer, R., Harwood, D., Ishman, S., and Webb, P. 1988. Micropale- Cooper, A.K., P. Barrett, K. Hinz, V. Traube, G. Leitchenkov, and H. ontological analyses of sediments from Crary Ice Rise. Antarctic Stagg. 1991. Cenozoic prograding sequences of the Antarctic Con- Journal of the U.S., 23(5), 34-36. tinental Margin: A record of glacio-eustatic and tectonic events. Webb, P.-N., T.E. Ronan, Jr., J.H. Lipps, and T.E. DeLaca. 1979. Marine Geology, 102, 175-213. Miocene glaciomarine sediments from beneath the southern Ross Cooper, A.K., S. Eittreim, U. Ten Brink, and I. Zayatz. 1993. Cenozoic Ice Shelf, Antarctica. Science, 203(4416), 435-437. glacial sequences of the antarctic continental margin as recorders Whillans, I.M., J. Bolzan, J., and S. Shabtaie. 1987. Velocity of ice of antarctic ice sheet fluctuations. In J.P. Kennett and D.A. Warnke streams B and C, Antarctica. Journal of Geophysical Research, (Eds.), The antarctic paleoenvironment: A perspective on global 92(B9), 8895-8902. Volcanic activity and seismicity of Mount Erebus, 1986-1994 RAYMOND R. DIBBLE, Victoria University of Wellington, Wellington, New Zealand PHILIP R. KYLE and MICHAEL J. SKOV, Department of Geoscience, New Mexico Institute of Mining and Technology, Socorro, New Mexico 87801 ount Erebus, a 3,794-meter (m) high, active volcano on 1985, when the lava lake was exhumed, small strombolian MRoss Island, Antarctica, has a permanent lake of molten eruptions have occurred at rates of between zero and at least anorthoclase phonolite magma in its inner crater. A 3-month eight per day. Between December 1986 and December 1990, period of sustained large strombolian eruptions starting in Victoria University of Wellington maintained surveillance of September 1984 buried the lake and ejected over 100,000 the lava lake (when cloud and solar battery power allowed) cubic meters of phonolite bombs and other ejecta. Since from a videocamera situated on the north rim of the main ANTARCTIC JOURNAL - REVIEW 1994 11 crater (Dibble et al. 1988). The video signal was radioed to (figure 1, right) and were about 10 m in diameter. Again, erup- Scott Base using a teleyision transmitter where it was tions were from the north lake, which convected less than the recorded on videotape. Following are brief descriptions of the south lake. The TV station was dismantled on 11 December volcanic activity and changes in the lava lake recorded using 1990. No observations were made during the 1991-1992 field the video monitoring system and ground-based surveillance season. In the 1992-1993 field season, rare small strombolian made during austral summer field seasons. eruptions occurred from two small lakes generally similar to In 1986-1987, there was one incandescent lake 2-10 m in those observed in November 1990. diameter near the center of the inner crater. It exploded like a On 19 October 1993, two large phreatic eruptions cannon about three times per day. By the austral summer of occurred. These are the first ever recorded at Mount Erebus, 1987-1988, the lake was on the north side of the inner crater. and they showered the north crater rim with pulverized It was 10 m in diameter and erupted large bursting globules of hydrothermally altered debris. The eruptions formed a new magma. A much smaller lava pool, which rarely erupted, crater about 50x20 m across near the edge of the main crater formed near the south side of the inner crater, and near the floor above the lava lakes (figure 2). The earthquakes that northwest side, steam revealed a third vent, which was hidden accompanied the eruptions gave seismograms with cigar- from the videocamera. A camera failure limited surveillance shaped envelops and had durations of around 1 minute. The during the austral summer of 1988-1989 until January 1989. At earthquakes were well recorded by a seismometer at that time, the north and south lakes were almost frozen over, McMurdo Station. A helicopter piloted by Lt. Bob Brodin was but in February, a lava flow from the south pool formed a lake flying along the flank of Mount Erebus at an altitude of about at least 15 m long. In April, both lakes were about 5 m across. 1,850 m and recorded the first eruption at about 16:46 (local By November 1989, a fauklike crack had appeared at the base time). The crew observed a black mushroom-shaped cloud of the west wall of the inner crater, and the floor appeared to rising vertically about a thousand meters above the crater. be subsiding on the north side. The south lake was 13 m Wind dispersed the cloud to the north. across and rarely erupted, but east-to-west magma convec- An array of six vertical 1 -hertz seismometers monitors the tion within the lake was common. The north lake was again seismicity associated with the volcanic activity. The data from frozen over, but between 18 and 25 December 1989, lava the array are recorded at the Mount Erebus Volcano Observa- flowed north-northwest from it. After this, frequent small tory (MEVO) at McMurdo Station using helicorders and a PC explosions occurred from the hidden northwest vent until computer running XDETECT, an International Association of mid-January. A line of small incandescent vents formed Seismology and Physics of the Earths Interior (IASPEI) event- between the south and north lakes in March 1990, ending on recording program. The digital recordings are automatically 26 March at 10:00 universal time (UT) in a violent explosion, transferred to a Sun workstation and (after compression) sent which joined all the lava lakes into one of 25 m diameter (fig- to New Mexico Institute of Mining and Technology and Victo- ure 1, left) with flow toward the north.
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