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Transcript of Hindsight Heresy
Examples of “Hindsight Heresy” in which a hypothesis is constructed after looking at a data set, and then using the same data to support and test the hypothesis, to prune the data or change parameters (Burke 2008; Torsvik at al. 2006; Lithgow-Bertelloni & Richards 1998; Courtillot et al 2003; Coutier et al. 2007; etc.).1. Courtillot, V. et al. Three distinct types of hotspots in the Earth's mantle. Earth Planet. Sci. Lett. 205, 295308 (2003).2. Torsvik, T.H. et al. 2006. Large igneous provinces generated from the margins of the large low-velocity provinces in the deep mantle. GJI 167, 1447–1460.3. Burke, K. et al. Plume generation zones at the margins of large low shear velocity provinces on the core–mantle boundary. EPSL 265, 49–60 (2008).4. Lithgow-Bertelloni, C., Richards, M.A., 1998. The dynamics of Cenozoic and Mesozoic plate motions. Rev. Geophys. 36, 27–78.5. Cottaar, S., B. Romanowicz, An unsually large ULVZ at the base of the mantle near Hawaii, EPSL, 355-356, 213-222, 2012.6. Courtier, A. M. and 14 others. Correlation of seismic and petrologic thermometers suggests deep thermal anomalies beneath hotspots. EPSL 264, 308-316.
100 km depth
Ridge, slab related
Using the same parameters as Burke, the correlation of hotspots & backtracked LIPs with tomography is higher for the uppermost than for the lowermost mantle
Slabs in TZ
11 hotspots on edges
Most hotspots are in broad ridge-related LVAsLIPs & some hotspots started at edges of slabs
6 ‘aberrant’ hotspots
14 ‘aberrant’ hotspots
Burke et al.
(“outside of plate boundary related low wavespeed areas)
true within-plate hotspots are underlain by average or fast mantle at 100 km depth.
100 km depth
Core-mantle boundary (CMB)
“Hotspots” correlate with upper mantle LVAs
There is a strong anticorrelation between the inferred positions of plate divergence, ridges, hotspots and LIP initiation & subduction zones over the last 250 Myrs and high wavespeed features in and just below the TZ.
Plates move over less dense hotter mantle as they move away from ridge
This explains seafloor flattening & residual bathymetry
Constrains thermal gradient
Constrains melt content