This study will use a three.dimensional gravity and magnetics interpretation of existing geophysical data near the northern end of the Mariana Trough, which appears to be actively undergoing the transition from rifted to spreading crust. The study will utilize bathymetric, gravity and magnetics to calculate standard geophysical parameters and to claculate a sea floor magnetization solution in this backarc basin. The PI will collaborate with the proposed and ongoiong structural and petrological work of P. Fryer (University of Hawaii) and scientists from the Geological Survey of Japan.