This award supports a project to use airborne ice penetrating radar and topographic information to map internal layering of the divide zone between the Amundsen Sea and Ross Embayment to search for evidence of divide migration. If collapse has been in progress for some time, it should be detectable in distortions of the layering. The project will use the Support Office for Aerogeophysical Research (SOAR) Twin Otter aircraft to map the ice along flow lines which cross the divide. The data will be used together with ice flow models to infer an ice divide migration history, obtain information about recent accumulation rate over planned traverse routes and will provide important information on time scale and layer thickness for the inland West Antarctic ice sheet ice coring project.