ReferencesAdams, C.J. 1986. Geochronological studies of the Swanson Forma-

tion of Marie Byrd Land, West Antarctica, and correlation withNorthern Victoria Land, East Antarctica, and South Island, NewZealand. New Zealand Journal of Geology and Geophysics, 29,345-358.

Adams, C.J., P. Broady, P.J. Cleary, and S.D. Weaver. 1989. Geologicaland biological expedition to Edward VII Peninsula, Marie ByrdLand, West Antarctica-1987/88: Field observations and initialresults. New Zealand Antarctic Record, 9(2), 5-34.

Adams, C.J., and S.D. Weaver. 1990. Age and correlation of metamor-phic basement in Edward VII Peninsula Marie Byrd Land, WestAntarctica, and correlation with Northern Victoria Land andSouthern New Zealand. Zentralblatt für Geologie und Paläontolo-gie, 1(112), 75-86.

Anderson, J.B. 1983. Preliminary results of the Deep Freeze 1983 pis-ton-coring program. Antarctic Journal of the U.S., 18(5), 157-158.

Beitzel, J.E. 1972. Geophysical investigations in Marie Byrd Land,Antarctica. (Unpublished Ph.D. thesis, University of Wisconsin.)

Bradshaw, J.D., P.B. Andrews, and B.D. Field. 1983. Swanson Forma-tion and related rocks of Marie Byrd Land and a comparison withthe Robertson Bay Group of Northern Victoria Land. In R.L. Oliver,P.R. James, and J.B. Jago (Eds.), Antarctica earth science. Canberra:Australian Academy of Science.

Bradshaw, J.D., I.W.D. Daiziel, V. DiVenere, S.B. Mukasa, R.B.Pankhurst, B.C. Storey, and S.D. Weaver. 1991. The southern rimof the Pacific: New work on the pre-Cenozoic rocks of Marie ByrdLand. In Abstracts-Sixth International Symposium on AntarcticEarth Sciences, 9-13 September, 1991. Tokyo: National Institute forPolar Research.

Cisowski, S., and B.P. Luyendyk. 1991. Paleomagnetic study ofigneous and metamorphic rocks from the Ford Ranges, MarieByrd Land, West Antarctica. EOS, Transactions of the AmericanGeophysical Union, 72(44), 129.

LeMasurier, W.E., and F.A. Wade. 1990. Fosdick Mountains. In W.E.

LeMasurier and J.W. Thomson (Eds.), Volcanoes of the antarcticplate and southern oceans (Antarctic Research Series, Vol. 48).Washington, D.C.: American Geophysical Union.

Luyendyk, B.P., S.M. Richard, C.H. Smith, and D.L. Kimbrough. 1992.Geological and geophysical investigations in the northern FordRanges, Marie Byrd Land, West Antarctica. In Y. Yoshida, K.Kaminuma, and K. Shiraish (Eds.), Recent progress in antarcticearth science. Tokyo: Terra Scientific.

Richard, S.M., and B.P. Luyendyk. 1991. Glacial flow reorientation inthe southwest Fosdick Mountains, Ford Ranges, Marie Byrd Land.Antarctic Journal of the U.S., 26(5), 67-69.

Richard, S.M., C.H. Smith, D.L. Kimbrough, P.G. Fitzgerald, B.P.Luyendyk, and M.O. McWilliams. In press. Cooling history of thenorthern Ford Ranges, Marie Byrd Land, West Antarctica. Tecton-ics.

Smith, C.H. 1992. Metapelites and migmatites at the granulite faciestransition, Fosdick metamorphic complex, Marie Byrd Land, WestAntarctica. In Y. Yoshida, K. Kaminuma, and K. Shiraish (Eds.),Recent progress in antarctic earth science. Tokyo: Terra Scientific.

van der Wateren, F.M. 1993. Personal communication.Wade, F.A., C.A. Cathey, and J.B. Oldham. 1977a. Reconnaissance

geologic map of the Guest Peninsula quadrangle, Marie ByrdLand, Antarctica. USARP: Antarctic Geologic Map, A-7.

Wade, F.A., C.A. Cathey, and J.B. Oldham. 1977b. Reconnaissancegeologic map of the Boyd Glacier quadrangle, Marie Byrd Land,Antarctica. USARP: Antarctic Geologic Map, A-6.

Wade, F.A., C.A. Cathey, and J.B. Oldham. 1977c. Reconnaissancegeologic map of the Alexandra Mountains quadrangle, Marie ByrdLand, Antarctica. USARP: Antarctic Geologic Map, A-5.

Wade, F.A., C.A. Cathey, and J.B. Oldham. 1978. Reconnaissance geo-logic map of the Gutenko Nunataks quadrangle, Marie Byrd Land,Antarctica. USARP: Antarctic Geologic Map, A- 11.

Weaver, S.D., J.D. Bradshaw, and C.J. Adams. 1991. Granitoids of theFord Ranges, Marie Byrd Land, Antarctica. In M.R.A. Thomson,J.A. Crame, and J.W. Thomson (Eds.), Geological evolution ofAntarctica. Cambridge: Cambridge University Press.

Mount Erebus Volcano Observatory: Seismic observationsMICHAEL J. SKov and PHILIP R. KYLE, Department of Geoscience, New Mexico Institute of Mining and Technology,

Socorro, New Mexico 87801

Seismometers were first deployed on Mount Erebus in1973; the first successful observations were made in 1974,

however, using an array of seismometers installed within 1kilometer (km) of the lava lake (Kyle et al. 1982). A permanentseismic network was established during the 1980-1981 fieldseason as part of the International Mount Erebus SeismicStudy (IMESS) (Rowe and Kienle 1986). The network has alsoincluded nonseismic instrumentation, including an inductionloop to examine the emission of electrically charged gasesand infrasonic detectors to capture explosion events (Dibbleetal. 1984).

During the 1992-1993 field season, major changes weremade to the Mount Erebus seismic monitoring system. Priorto this field season, the seismic data was radio-te!emetered toNew Zealand's Scott Base where it was recorded on an analog,multichannel, magnetic tape recorder (Kienle et al. 1981).This system was replaced by a personal-computer based, dig-

ital data-acquisition system, providing, for the first time, theability to transfer seismic data from Mount Erebus to theUnited States daily. Prior to the installation of the digital data-acquisition system, seismic data could be retrieved only dur-ing the austral summer months when flights off the ice arepossible.

The network currently consists of six, short-period, verti-cal-component seismometers arranged into two triangles.One triangle is located around the summit region; the second,lower on the mountain. These stations employ very-high-fre-quency radio-telemetry to transmit data to the recording sys-tem at McMurdo Station. A seventh station is temporarilylocated in McMurdo and is wired directly to the data logger.

The digital recording system is based on a design by agroup within the International Association of Seismology andPhysics of the Earth's Interior (IASPEI). This design employs a16-channel, 12-bit analog-to-digital converter and event-trig-

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gering software optimized for the detection of local earth-quakes (Lee 1989). The system samples the data stream fromthe seven seismometers, plus an Inter-Range InstrumentationGroup (IRIG-E) clock signal, approximately 100 times per sec-ond, providing a high-quality, well-timed digital recording.

Although the data logger provides high-quality digitalrecording, the more important benefit is the ability to pack-age the data for transmission to the United States. Becausethe data logger makes use of a triggered recording system,each seismic event is packaged into a relatively small data file,which can be transmitted easily via the recently completedINTELSAT satellite communication system. Once per day,data files are transferred from the personal computer datalogger to a Sun Sparcstation 2 in McMurdo's Crary Lab Com-puting Facility. The Sparcstation assembles the data into apacket suitable for transmission and employs the File Trans-fer Protocol (FTP) to transfer the data to a Sun Sparcstation 2in Socorro, New Mexico. Once in Socorro, the data files areprocessed, reviewed, and archived for future research.

An effort is being made to identify the many types ofrecorded events more accurately, including relatively deepevents, thought to be associated with the movement ofmagma, and very shallow events, which are often a result ofsmall explosions in the lava lake. In addition, several eventshave been identified that are not directly related to volcanicactivity. Microseisms, caused by offshore storms, are com-monly observed on seismograms from Mount Erebus, partic-ularly during January and February. Seismograms showingthe movement of ice can appear deceptively similar to seis-mic events of volcanic origin and, thus, need to be under-stood and identified more precisely.

Daily access to seismic data from Mount Erebus is animportant safety feature of this system. Although a violenteruption of Mount Erebus is highly unlikely, it is an active vol-cano and, as such, should be monitored. For the first time, vol-canologists and seismologists in the United States can exam-ine the seismic events from Mount Erebus on a daily basis.

In addition to the use of this system as a monitor of seis-mic activity, the data logger can be expanded for other scien-tific investigations. Considerations were made for the possi-

ble expansion of the seismic array, including the addition ofmore seismic stations and the possible inclusion of three-component instruments. The data logger's software triggercould be replaced with one optimized for teleseismic eventdetection, a design that could provide data useful for tomo-graphic studies. Future expansion may include the deploy-ment of weather stations near one or more seismic stations,providing wind and temperature information to accompanythe seismic data.

The digital recording system represents a new expansionfor the Mount Erebus Volcano Observatory. The data this sys-tem provides should assist researchers in gaining a betterunderstanding of volcanic processes at Mount Erebus.

This work was supported by National Science Founda-tion grant OPP 91-18056. We thank the helicopter crews ofVXE-6 squadron for their support in servicing the seismic sta-tions on Mount Erebus. Special thanks to Sarah Doherty forher assistance during the antarctic winter of 1993. We thankthe many other people who assisted with this work, and weextend our thanks to Antarctic Support Associates, Paul Rose,and Bill McIntosh.

References

Dibble, R.R., J. Kienle, P.R. Kyle, and K. Shibuya. 1984. Geophysicalstudies of Erebus Volcano, Antarctica, from 1974 December to1982 January. New Zealand Journal of Geology and Geophysics, 27,425-455.

Kienle, J., P.R. Kyle, S. Estes, T. Takanami, and R.R. Dibble. 1981. Seis-micity of Mount Erebus, 1980-1981. Antarctic Journal of the U.S.,16(5),35-36.

Kyle, P.R., R.R. Dibble, W.F. Giggenbach, and I. Keys. 1982. Volcanicactivity associated with the anorthoclase phonolite lava lake,Mount Erebus, Antarctica. In C. Craddock (Ed.), Antarctic geo-science. Madison: University of Wisconsin Press.

Lee, W.H.K. 1989. IASPEI software library volume 1: Toolbox for seis-mic data acquisition, processing and analysis. El Cerrito, Califor-nia: International Association of Seismology and Physics of theEarth's Interior in Collaboration with Seismological Society ofAmerica.

Rowe, C.A., and J. Kienle. 1986. Seismicity in the vicinity of RossIsland, Antarctica. Journal of Geodynamics, 6, 375-385.

Geochemistry of McMurdo Group volcanic rocksSTANLEY R. HART, Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole,

Massachusetts 02543PHILIP R. KYLE, Department of Geoscience, New Mexico Institute of Mining and Technology, Socorro, New Mexico 87801

Voting Cenozoic volcanic rocks from Marie Byrd LandJL (Futa and LeMasurier 1983) and from Scott and Balleny

islands (Hart 1988) are unusual because they show strontium-87/strontium-86 (87Sr/ 86Sr) ratios lower than most oceanicisland basalts, some values approaching those typical of mid-ocean ridge basalt (MORB). To assess the geographic extent of

this low 87Sr/ 86Sr province and to decide whether a MORB-type mantle is involved, we have analyzed a reconnaissancesampling of basalts from the Hallett volcanic province, north-ern Victoria Land, for Sr, neodymium (Nd), and lead (Pb) iso-topic ratios. These data are shown in figure 1; data for basaltsfrom Peter I Island, Jones Mountains, and Marie Byrd Land

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