Deception Island is a large mainly basalt—andesite Antarctic volcano at the western end of Bransfield Strait, a very young (< 4 Ma) marginal basin situated at the northern end of the Antarctic Peninsula. It has a submerged basal diameter of c. 30 km and rises to 500 m at Mt Pond. It was one of the first parts of Antarctica to be discovered, probably in 1820 by UK and USA sealers and is historically and politically important: it is credited as the location from which Nathaniel Palmer first observed the Antarctic continent, a basis for the American claim to discovering Antarctica (disputed by UK and Russia, of course). It has the longest history of human occupation of any site in Antarctica, including as a whaling station for the first c. 30 yrs of the 20th century, as the site of a British scientific station (from 1944), then Chilean and Argentine stations (from the 1950’s). Eruptions in 1967 then 1969 & 1970 destroyed the British and Chilean stations and post-1967 occupation is by Argentine and, from the late 1980’s, Spanish stations only and summer-only. The Spanish station carries out volcano monitoring via seismic instruments for c. 2 months each summer.
Evidence for the earliest activity comprised shoaling and emergence via multiple centres with Strombolian-like deposits and a single large lava shield. However, Deception Island is dominated by a 9 km diameter caldera flooded by the sea to which access is permitted via a spectacular narrow breach in the sea cliffs known as Neptunes Bellows. The caldera formed following the largest-known Antarctic eruption that expelled 30-60 km3 of magma. The age of the eruption is unknown. Evidence for two discrete magma types in the juvenile components suggests that influx of a separate magma batch may have triggered the climactic eruption but there is also a strong regional tectonic imprint on the island that may also have played a part. Pyroclastic density current deposits were draped over the entire island and it was probably enlarged by c. 7-10 km beyond the current coastline. Characteristics of those deposits indicate a major involvement of seawater in the eruption and it probably had a low dense eruption column as a result. Post-caldera activity comprised numerous small pyroclastic cones. Tuff cones and maars formed around the inner shores of the caldera whilst scoria cones were constructed at higher drier elevations, occasionally accompanied by lava effusion that constructed small lava-fed deltas into the sea at many locations. Many of the phreatomagmatic eruptions were extremely violent and tephra was distributed right across the Scotia Sea and as far as the South Pole, c. 3000 km distant. The wide geographical distribution of Deception tephras is probably helped by the much lower elevation of the tropopause above Antarctica compared with lower latitudes.
A spectacular fire-fountaining fissure eruption was observed in 1842. During the 20th century, a batch of eruptions occurred between 1906 and 1912 but were unobserved and are represented only as tephra layers in the Mt Pond ice cap. However, eruptions in 1967 and 1969 were observed and, together with the impacts of an eruption in 1970, are relatively well documented. They occurred from fissures within the caldera (where all post-caldera activity is focused) and varied from submarine to subglacial and subaerial. Seismic crises in 1992 and 1999 are attributed to significant magma migrations that did not result in an eruption. Continual small-scale tremors are due to adjustments of the hydrothermal system linked to a magma chamber at depths, possibly as shallow as 1.2 km.
About 20 000 tourists visit Deception Island during the short Antarctic summer, making it the most visited locality in the entire continent.
CVG Research on Deception Island:
None currently ongoing – open to suggestions.
Key References on Deception Island:
- Baker, P.E., McReath, I., Harvey, M.R., Roobol, M.J. & Davies, T.G. 1975. The geology of the South Shetland Islands: V. Volcanic evolution of Deception Island. British Antarctic Survey Scientific Reports 78, 1-81.
- Keller, R.A., Fisk, M.R., White, W.M. & Birkenmajer, K. 1992. Isotopic and trace element constraints on mixing and melting models of marginal basin volcanism, Bransfield Strait, Antarctica. Earth and Planetary Science Letters 111, 287-303.
- Smellie, J.L., Hofstetter, A. & Troll, G. 1992. Fluorine and boron geochemistry of an ensialic marginal basin volcano: Deception Island, Bransfield Strait, Antarctica. Journal of Volcanological and Geothermal Research 49, 255-267.
- Martí, J., Vila, J. And Rey, J. 1996. Deception Island (Bransfield Strait, Antarctica): an example of a volcanic caldera developed by extensional tectonics. Geological Society, London, Special Publications 110, 253-265.
- Cooper, A.P.R., Smellie, J.L. and Maylin, J. 1998. Evidence for shallowing and uplift from bathymetric records of Deception Island, Antarctica. Antarctic Science 10, 455-461.
- Moreton, S. & Smellie, J.L. 1998. Identification and correlation of distal tephra layers in deep sea sedimentary cores, Scotia Sea, Antarctica. Annals of Glaciology 27, 285-289.
- Pallas, R., Smellie, J.L., Casas, J.M. & Calvet, J. 2001. Using tephrochronology to date temperate ice: correlation between ice-tephras on Livingston Island and eruptive units on Deception Island volcano (South Shetland Islands, Antarctica). The Holocene 11, No. 2, 149-160.
- Smellie J.L. (2001): Lithostratigraphy and volcanic evolution of Deception Island, South Shetland Islands. Antarctic Science 13 (2): 188-209.
- Smellie, J.L. 2002. The 1969 subglacial eruption on Deception Island (Antarctica): events and processes during an eruption beneath a thin glacier and implications for volcanic hazards. Geological Society, London, Special Publication 202, 59-79.
- Smellie, J.L. et al. (2002): Geology and geomorphology of Deception Island. BAS GEOMAP Series, Sheets 6-A and 6-B, 1:25 000, supplementary text, 77 pp. Cambridge, British Antarctic Survey.
- Keller, R.A., Fisk, M.R., Smellie, J.L., Strelin, J.A. & Lawver, L.A. 2002. Geochemistry of back-arc basin volcanism in Bransfield Strait, Antarctica: subducted contributions and along-axis variations. Journal of Geophysical Research 107 (B8), 10.1029/2001JB000444.
- Somoza, L., Martinez-Frias, J., Smellie, J.L., Rey, J. & Maestro, A. 2004. Evidence for hydrothermal venting and sediment volcanism discharged after recent short-lived volcanic eruptions at Deception Island, Bransfield Strait, Antarctica. Marine Geology 203, 119-140.
- Zandomeneghi, D., Barclay, A.H., Almendros, J., Ibáñez, J.M., Ben-Zvi, T., Wilcock, W.S.D. and the Tomodec Working Group. 2007. Three-dimensional P wave tomography of Deception Island volcano, South Shetland Islands. In: Antarctica: a keystone in a changing world – Online proceedings of the 10th ISAES X (Cooper, A.K., Raymond, C.R. et al. (eds)). USGS Open-File Report 2007-1047, Extended abstract 025, 4 pp.