Edge Driven Convection and Iceland
One of the alternative hypotheses for hotspot volcanism is Edge-Driven Convection (EDC). A small-scale convective instability forms at any step or discontinuous change in thickness in a thermal boundary layer [e.g., Elder, 1976]. The EDC hypothesis envisions that this instability will form at bounda...
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| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.536.6707 http://www.mantleplumes.org/Penrose/PenPDFAbstracts/King_Scott_abs.pdf |
| Summary: | One of the alternative hypotheses for hotspot volcanism is Edge-Driven Convection (EDC). A small-scale convective instability forms at any step or discontinuous change in thickness in a thermal boundary layer [e.g., Elder, 1976]. The EDC hypothesis envisions that this instability will form at boundaries between stable cratons and oceanic, or young continental, lithosphere [e.g., King and Anderson, 1995; 1998]. Because this is a relatively weak instability, large lat-eral variations in temperature or fast plate-scale flow can overwhelm EDC instabilities. (These same factors would also overwhelm most plume instabilities.) In the Central Atlantic, seismic tomography supports the EDC hypothesis–seismically fast anomalies (presumably cold down-wellings) are observed at the edge of the South American and West African cratons (Figure 1) just where we would expect the downwelling limbs of EDC to be located. King and Ritsema [2000] conclude that many, if not all, of the off-ridge Central and South Atlantic hotspots could be explained by EDC. The question remains, “Can an EDC mechanism explain the excess volcanism at Iceland (and the Azores)? ” The answer is not as clear as we would like, yet it is premature to throw out the EDC hypothesis. The biggest obstacle to considering the EDC hypothesis for Iceland is |
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