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Seismic evidence that the source of the Iceland hotspot lies at the core-mantle boundary

Helmberger, D. V. and Wen, L. and Ding, X. (1998) Seismic evidence that the source of the Iceland hotspot lies at the core-mantle boundary. Nature, 396 (6708). pp. 251-255. ISSN 0028-0836. doi:10.1038/24357.

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Although Morgan proposed in 1971 that hotspots such as Iceland were the result of hot, rising mantle plumes, it is still debated whether plumes originate from a thermal boundary just above the core-mantle boundary or at the base of the upper mantle. Although seismic evidence of plumes in the upper mantle is accumulating, narrow plume conduits in the deep mantle have yet to be detected. Details of plume formation in the lower mantle have therefore remained largely unconstrained. Here, however, we present seismic evidence for the presence of a localized patch of material with ultra-low seismic wave speed, located at the core-mantle boundary beneath the Iceland hotspot, and propose that this zone represents the hot, partially molten source region of the Iceland mantle plume. Through the modelling of seismic waveforms, we constrain the seismic velocity structure at this patch of the core-mantle boundary using a numerical-analytical interfacing code5 designed to reproduce the complex interference of shear-wave phases transmitted through, and refracted at, the boundary. Although this structure is difficult to constrain precisely, our preferred model consists of a dome which is 250 km wide, 40 km high and contains P- and S-wave velocity (wave-speed) reductions of 10% and 30%, respectively.

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Additional Information:© 1998 Macmillan Publishers Ltd. Received 4 September 1997; accepted 10 September 1998. We thank J. Ritsema for comments on early drafts. This work was supported by the NSF.
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Issue or Number:6708
Record Number:CaltechAUTHORS:20130402-103002791
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Official Citation:Helmberger, D. V., L. Wen, et al. (1998). "Seismic evidence that the source of the Iceland hotspot lies at the core-mantle boundary." Nature 396(6708): 251-255.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:37717
Deposited By: Tony Diaz
Deposited On:12 Apr 2013 00:00
Last Modified:09 Nov 2021 23:30

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