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| Structure | Volcanics | Refl. Seismic | Thickness | Heat Flow |
Crustal Thickeness
Refraction and reflection seismic data, as well as gravity data, provide important constraints on the thickness of the crust in the TAM, the Ross Embayment, and Marie Byrd Land. The crust is greater than 40 km thick beneath the TAM, thins to about 20 km beneath the Ross Embayment, and thickens again to about 32 km beneath Marie Byrd Land. Figure 18 shows a schematic crustal cross-section across the TAM and the Ross Embayment.
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| Figure 18. Schematic cross-section across the TAM and the Ross Embayment based on gravity data and relfection and refraction seismic data. Note that the base of the Victoria Land Basin reaches almost to the Moho. The vertical dashed line indicates that the thickness of the crust changes by up to 20 kilometers across the TAM front. The dip of the Moho in this region is poorly constrained, but is probably not vertical. Behrendt et al., 1991. | ||||
The thin crust beneath the Ross Embayment is consistent with a rift setting. The somewhat thicker crust beneath Marie Byrd Land has led to the suggestion that it is analogous to the Basin and Range.
An extremely large gravity anomaly of 200 mGal exists across the TAM and into the Ross Embayment. Modeling of this anomaly has lead to the interpretation of 40 km thick crust beneath the TAM (Figure 19).
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| Figure 19. A crustal model that fits the observed gravity data. Behrendt et al., 1991. | ||||
Figure 20 shows the area of Antarctica that would be below sea level if the ice were removed from the continent. Note that most of West Antarctica would be below sea level due to the relatively thin crust in this series of continental blocks.
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| Figure 20. Map showing areas of West Antarctica that would lie below sea level if ice were removed from the continent (diagonal pattern). http://www-bprc.mps.ohio-state.edu/ANTWGGG/tamrpt.html | |||