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Victoria University Antarctic Research Expedition Science and Logistics Reports 1994-95: VUWAE 39

1. Summary

page 1

1. Summary

The Transantarctic Mountains form one the highest and longest mountain chains in the world. Mechanisms for forming the mountains are debated, though it is believed that the mountains are a result of rifting between East and West Antarctica. The boundary between East and West Antarctica is marked by where the mountains meet the Ross Ice Shelf/Ross Sea. The occurrence of rifting suggests that at the mountain front a depression, or graben, should exist in the West Antarctic crust.

During December 1994, the K044 geophysical traverse collected data on the Ross Ice Shelf intended to enhance and extend the image of the crustal structure of the boundary between East and West Antarctica that resulted from the 1990/91 Seismic Experiment on the Ross Ice Shelf ("Seris", see ten Brink et al, 1993). The traverse at ~82°S covered a total distance of almost 200 km, starting at the edge of the Transantarctic Mountains and moving north-east onto the Ross Ice Shelf.

Data collected included GPS data for navigation and position finding, gravity data, magnetic data and radio echo sounding measurements of ice thickness.

The gravity data collected confirms earlier data and has initially shown some interesting features on the new portion of the traverse, though at this stage it is unclear what these variations represent. It is possible that the variations seen could be associated with the graben that was not imaged during the 1990/91 work closer to the mountain front.

Measurements of the Earth's magnetic field were made over the length of the traverse, such data were not collected on the earlier traverse. Once effects from the daily variation in the magnetic field and the general shape of the background field have been removed, we expect to see magnetic anomalies relating to the transition between West and East Antarctic crust.

Measurements of ice thickness made with an ice penetrating radar suggest that the Ross Ice Shelf becomes thinner away from the mountains, a result that would be expected given that further from the mountains, ice is further from its source. The main purpose of the radar measurements was to make ice thickness measurements up the Robb Glacier. Such measurements would have been used in reprocessing of seismic data from the 1990/91 traverse. However poor weather and time constraints meant that this part of the event was not carried out.

Future work may involve making the ice thickness measurements not achieved this year on the Robb Glacier, along with magnetic measurements. It is also feasible that a larger seismic expedition could be carried out should results from the Seris-A traverse suggest this is warranted. Such an expedition could easily be extended still further across the Ross Ice Shelf.