Subglacial West Antarctic volcanoes defined by aerogeophysical data and the potential for associated hydrothermal systems
Subglacial hydrothermal systems beneath the West Antarctic Ice Sheet (WAIS) are important objects of research because meltwater associated with them can act as a lubricant beneath this potentially unstable ice sheet. In addition, subglacial hydrothermal systems on Earth may provide analogues for sub...
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| Format: | Thesis |
| Language: | English |
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2008
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| Online Access: | https://hdl.handle.net/2152/85451 https://doi.org/10.26153/tsw/12415 |
| Summary: | Subglacial hydrothermal systems beneath the West Antarctic Ice Sheet (WAIS) are important objects of research because meltwater associated with them can act as a lubricant beneath this potentially unstable ice sheet. In addition, subglacial hydrothermal systems on Earth may provide analogues for subglacial microbial habitats under the polar caps of Mars or other icy bodies. The West Antarctic subglacial volcanoes compared herein display a range of plausible hydrothermal systems. One end-member is Mt. CASERTZ which is a recently erupted subglacial volcano discovered in the early 1990's just upstream of a well lubricated ice stream. It sustains a depression in the ice surface, and it is associated with nearby subglacial lakes. Therefore, it has a high potential for sustaining a short-lived hydrothermal system. At the other end of the spectrum of plausible subglacial hydrothermal systems is a subglacial volcano, designated M, which appears to be inactive and to possess no substantial hydrothermal system. In the middle of the spectrum is a subglacial volcano, designated L, which lies near the ice divide between the Ross Sea and Amundsen Sea Embayments in West Antarctica. It has a well-defined intrusive body and a terraced morphology consistent with multiple eruptions. Subglacial Volcano L is distinctly larger than the other two volcanoes, and it is probably a greater heat source than M while being older than Mt. CASERTZ. Using newly developed radar techniques, I observed that Volcano L has several small (200-500 meter) subglacial lakes located over and on the boundaries of the modeled underlying intrusive body implying the intrusive body is associated with subglacial melting. Adjacent to volcano L, I also observed a large drawdown (designated H) in the internal layers of the ice sheet consistent with substantial basal melting. To better evaluate ice mass loss associated with anomaly H and Volcano L, I developed an algorithm that maps anticorrelations between internal layers within an ice sheet and subglacial topography. Using this algorithm, I discovered that the layer drawdown adjacent to L extended along a highly linear zone about 28 kilometers in length. The layer drawdown near Volcano L implies a mass loss at the base of the ice sheet of 25 cubic kilometers. This mass flux can be explained by localized subglacial melting associated with igneous processes. If the mass flux is due to local subglacial melting, then subglacial lakes identified on either side of the drawdown are hydraulically plausible destinations for the meltwater. I hypothesize that the linear zone associated with anomaly H is a fault supplying an avenue for the movement of magma to the base of the ice sheet that supports an associated hydrothermal system. Together these factors make the subglacial lakes that I have observed on Volcano L and adjacent to the hypothesized fault highly attractive targets for geochemical and biological sampling of a mature subglacial hydrothermal system Geological Sciences |
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