Geodynamics Seismology Plumes Gillian R Foulger University of

Geodynamics, Seismology & Plumes Gillian R. Foulger University of Durham, UK

The classical model 2

The alternative model 3

Plume Plate 4

How can we test these hypotheses?

Model Predictions Plume 1. 2. 3. 4. Uplift “Plume head” eruption “Plume tail” to the CMB Time-progressive volcano chain 5. High temperature Plate 1. Extension 2. Volume: source fusibility 6

Seismology

Downwellings (slabs)

Ritsema et al. (1999) 9

Ritsema et al. (1999) 10

Upwellings (plumes)

The “Superplumes” 12

The “Superplumes” are not hot. They are dense, chemical anomalies. Vs Density Trampert et al. (2004) 13

Smaller-scale features

The Iceland mantle plume 15

… oops … where did it go? 16

Truncation & colour scales Bijwaard & Spakman (1999) Hudson Bay plume? 17

Problems with tomography • Insufficient resolution • Poor data coverage • Ambiguity in interpretation 18

Resolution Pilidou et al. (2005) 19

Poor data coverage “Finite-frequency” tomography (“banana doughnut” tomography) 20

Finite frequency tomography Montelli et al. (2004) 21

“plumes” = seismic stations van der Hilst & de Hoop (2005) 22

Ambiguity in interpretation • Phase – Mineral – State • Composition • Temperature 23

Basin & Range Province, USA 24

Azores

Huge vertical exaggerations 200 km Silveira & Stutzmann (2002) 26

Azores plume tail? P-wave model no S-wave model Yang (2006) 27

… and a plate model for the Azores?

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Resources http: //www. mantleplumes. org/ 31

That’s all folks