This research was supported by grants from USSAC-JOI to C.E. Lesher and K.V. Cashman (Leg 163) and by the U.S. National Science Foundation (EAR-94-19382 to CEL and EAR-95-08144 to KVC). The Danish Lithosphere Center provided support to CEL during the final preparation of this manuscript. We thank J. Kauahikaua and M. Mangan for their thorough reviews.