The 1969 subglacial eruption on Deception Island (Antarctica): events and processes during an eruption beneath a thin glacier and implications for volcanic hazards
Published:January 01, 2002
J. L. Smellie, 2002. "The 1969 subglacial eruption on Deception Island (Antarctica): events and processes during an eruption beneath a thin glacier and implications for volcanic hazards", Volcano–Ice Interaction on Earth and Mars, J. L. Smellie, M. G. Chapman
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A short-lived eruption of basaltic andesite to andesite on Deception Island in 1969 occurred from a series of fissures underneath a glacier. The glacier was thin (c. 100 m) and the eruption created a large and sudden discharge of meltwater that overflowed the glacier, severely damaging buildings on the island. The eruption was unusually well documented and it illustrates several features of subglacial eruptions that are only poorly known and not well understood. In particular, overflowing meltwater is contrary to predictions based on existing simple hydrological models for eruptions beneath thin glaciers. The eruption is analysed in this paper and used as a model for the fluid dynamics and thermodynamics of eruptions beneath a thin glacier mainly composed of impermeable ice. It is suggested that, in eruptions of relatively fluid magmas with a low magma rise rate, volatiles and magma are able to decouple and subglacial melting is strongly influenced by the superheated magmatic and hydrothermal gases (mainly steam). Thus, melting is much faster than that due solely to coupled conductive (magma) and convective (meltwater) heat transfer. The influence of gasdriven melting also has an important effect on the shape of the meltwater cavity and may be at least partly responsible for the cylindrical ice chimneys developed above vents on Deception Island. The results of the study are important for reconstructing the shapes of englacial cavities melted above a vent. They also highlight the importance of glacier structure and densification, rather than simply glacier thickness, in determining the hydraulic evolution of an eruption. Even eruptions beneath thin glaciers can generate significant meltwater floods.
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Volcano–Ice Interaction on Earth and Mars
This volume focuses on magmas and cryospheres on Earth and Mars and is the first publication of its kind to combine a thematic set of contributions addressing the diverse range of volcano-ice interactions known or thought to occur on both planets. Understanding those interactions is a comparatively young scientific endeavour, yet it is vitally important for a fuller comprehension of how planets work as integrated systems. It is also topical since future volcanic eruptions on Earth may contribute to melting ice sheets and thus to global sea level rise.
Papers included here are likely to influence the choice of sites for future Mars missions in exobiologically important areas. On Earth, snow and ice are widespread, not only in extensive icecaps but also as alpine glaciers at high elevations in tropical regions. By contrast, Mars today is an arid volcanic planet with only small polar ice-caps although an abundance of water is believed to be trapped in the cryolithosphere. It is also thought that the planet may have sustained extensive frozen oceans early in its history. The presence of a former hydrosphere, a cryosphere and coincident volcanism thus make Mars the likeliest prospect for the first discoveries of life away from Earth. Much research has assumed that terrestrial volcano-ice systems are plausible analogues for putative Martian examples, but until mankind finally sets foot on Mars, there is no simple test for that assumption.
Our hope is that the knowledge presented here will stimulate research among planetary geologists in this exciting, rapidly expanding field for many years to come.