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Crustal material is returned to the upper mantle in convergent margins via sediment subduction or trenchward erosion of the forearc by the downgoing plate (ie, subduction erosion). The active Aleutian arc is currently classified as an accreting margin as most of the arc has a well-developed accretionary prism that formed in the Pliocene. Geochemistry of Pliocene-Recent lavas in the central Aleutian arc indicates significant sediment involvement during magma genesis. However, prior to the late Pliocene, the Aleutian arc was in a long-term state of episodic forearc subduction erosion with minor involvement of subducted sediment compared to that since the late Pliocene. The central Aleutian volcanic front has migrated northwards tens of kilometers since the construction of the broad arc massif by voluminous volcanism during arc inception in the early to mid-Paleogene. We have recently added more than forty new …