Analysis of a shear zone where a tractor fell into a crevasse, western side of the Ross Ice Shelf, Antarctica

The site of a tractor fall into a crevasse in the transition between ice sh elves is investigated. Two satellite images of the McMurdo Ice Shelf and Ro ss Ice Shelf junction are used to map features and processed to obtain velo cities and strain rates. The accident occurred at a minor maximum in strain rate, occurring in a flow trace originating at the side of an outlet glaci er from the Transantarctic Mountains. The flow trace ice has been altered i nto surface rollers that are parallel with ice motion. The surface rollers would seem to be a major reason for the tractor fall. On a larger scale, me asured strain rates are used in a calculation of the budget of forces for t he Ross Ice Shelf. The resistive forces to flow as deduced from the new and old measurements are insufficient to balance the gravitational driving for ce. There must be major resistive forces from other sites, such as Minna Bl uff and Cape Crozier. (C) 2001 Elsevier Science B.V. All rights reserved.