BREAKDOWN OF SEAMOUNTS AT THE TRENCH AXIS, VIEWED FROM GRAVITY-ANOMALY

The Daiichi-Kashima seamount in the Japan trench and a wedge shaped se amount in the Ogasawara trench are good examples that the seamount bre aks down and sink at the axis of the trench. We estimated subterranean structure of these seamounts using gravity anomaly and topography, an d proposed a model, Disappearance of a deep root of the mountain in th e upper mantle supporting the mass of the mountain, can explain the ph enomena. It is suspected that main reason of disappearance of the root is due to compression caused by the bending of the plate near the tre nch.