Report on Deception Island (Antarctica) — April 1997
Bulletin of the Global Volcanism Network, vol. 22, no. 4 (April 1997)
Managing Editor: Richard Wunderman.
Deception Island (Antarctica) Seismicity lower than previously recorded
Please cite this report as:
Global Volcanism Program, 1997. Report on Deception Island (Antarctica) (Wunderman, R., ed.). Bulletin of the Global Volcanism Network, 22:4. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199704-390030.
63.001°S, 60.652°W; summit elev. 602 m
All times are local (unless otherwise noted)
The following describes work completed during the 1996-97 austral summer, carried out from 6 December 1996 to 25 February 1997. The survey scientists deployed magnetometer instruments, gravimeters, and a meteorological station.
Seismicity (figure 11) was monitored with a digital seismic array with 16-bit dynamic range. The array included 24 geophones (24 Mark L4C-L25b). The array was placed in the same location as the 1994-95 and 1995- 95 surveys (BGVN 20:04 and 21:04) but in addition four additional seismometers were installed in active areas of the island to gather information on the spectral characteristics of the volcanic events. The recorded seismic activity was lower in both energy level and number of events than for the previous years.
|Figure 11. Daily occurrence of earthquakes at Deception Island, 6 December 1996-25 February 1997. Courtesy of A. García.|
The recorded events included six intermediate-focus earthquakes, eight regional earthquakes, 13 events with S-P arrival times smaller than 5 seconds and M 2.5, and five volcanic tremors. There were also 119 long-period events and 43 hybrid events, some of which had S-P arrival times under 1 second.
Scientists investigated fumarole geochemistry, thermal anomalies, and rock rheology. Temperatures of hot soils remained stable with respect to the last survey. Anhydrous gas compositions were mainly CO2 (96-99%) and H2S (0.2-3.9%), with no SO2 detected.
Geologic Background. Ring-shaped Deception Island, one of Antarctica's most well known volcanoes, contains a 7-km-wide caldera flooded by the sea. Deception Island is located at the SW end of the Shetland Islands, NE of Graham Land Peninsula, and was constructed along the axis of the Bransfield Rift spreading center. A narrow passageway named Neptunes Bellows provides entrance to a natural harbor that was utilized as an Antarctic whaling station. Numerous vents located along ring fractures circling the low, 14-km-wide island have been active during historical time. Maars line the shores of 190-m-deep Port Foster, the caldera bay. Among the largest of these maars is 1-km-wide Whalers Bay, at the entrance to the harbor. Eruptions from Deception Island during the past 8700 years have been dated from ash layers in lake sediments on the Antarctic Peninsula and neighboring islands.
Information Contacts: A. Garcia, M. Astiz, and M. T. Villeguas, Depto. Volcanolog¡a, Museo Nacional de Ciencias Naturales, C.S.I.C. José Gutierrez Abascal 2, 28006 Madrid, Spain; J.M. Ibañez, J. Norales, and E Carmona, Instituto Andaluz de Geofísica, Apartado 2145, University of Granada, Granada, Spain; A. Caselli, G. Badi, and A. Baraldo, Instituo Antártico Argentino, Cerrito 1248, Buenos Aires, Argentina.