Contrasting Mantle Plume Structure: Imaging Hawaii, Iceland and Yellowstone

Wednesday, 17 December 2014: 5:45 PM
Richard M Allen, Cheng Cheng and William Bythewood Hawley, UC Berkeley Seismological Laboratory, Berkeley, CA, United States
Regional seismic images of hotspot regions are now providing detailed constrains on the upper-mantle structure driving these volcanic sources. Comparing the observed structure in different regions reveals a complexity to mantle plume structure, and their interaction with the over-riding lithosphere, that we are only beginning to understand. Beneath Hawaii, at the top of a near-vertical conduit extending from the lower mantle, we observe two horizontal layers to the present-day plume pancake structure. The first is at ~410 to ~250 km depth, and the second extends from ~150 km to the base of the lithosphere. Beneath Iceland the plume pancake appears to consist of only a single layer from ~200 km to the Moho. Beneath Yellowstone there is also only a single layer pancake, but it fills a layer from 300 km depth up to the Moho. These differences are likely the result of both different source chemistry, and also differences in the over-riding lithospheric structure. In this presentation we will explore the upper mantle structure of all three plumes and the possible explanations for these variations.