Several types of geophysical observations indicate that the lithosphere in the southcentral Pacific is undergoing diffuse north-south extension. As a partial test of this hypothesis, the Principal Investigator will survey a previously uncharted series of echelon ridges that extend for over 2500 km from the East Pacific Rise to the northern edge of the Tuamotu archipelago. A major implication of the stretching hypothesis is that some volcanic activity in the west Pacific may be related to tensional failure of the lithosphere rather than numerous mantle plumes. The goals of the survey are to first establish that the ridges exist where they have not been charted, and that they are continuous. The ridges will also be dredged for petrologic and age studies, and the magnetic signature of the ridges will be determined.
