Other
Scientific paper
Dec 2002
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002agufm.s11a1103h&link_type=abstract
American Geophysical Union, Fall Meeting 2002, abstract #S11A-1103
Other
3210 Modeling, 3230 Numerical Solutions, 8109 Continental Tectonics: Extensional (0905), 8121 Dynamics, Convection Currents And Mantle Plumes, 8450 Planetary Volcanism (5480)
Scientific paper
Seismic investigations of the Salt River Plain show that the axis of the Yellowstone hotspot track is underlain by a low velocity zone that is flanked on either side by high velocity material. If the structure along a hotspot track were produced by a deep-seated plume, then thermal effects alone would produce a broad slow velocity region. An alternative mechanism for generating small-scale volcanism is runaway asthenospheric instabilities driven by melt and residuum buoyancy [Tackley and Stevenson, 1993] and investigated recently using three-dimensional numerical modeling. In this scenario, the slow region is produced by the presence of partial melt, while the high velocity regions are produced by the pushing aside of melt-depleted residuum. Under the influence of plate motion, such small-scale convective instabilities tend to form rolls and align themselves in the direction of plate motion, and so present an attractive alternative to the plume hypothesis for the origin of hot spots. Special conditions are required, however, for this mechanism to exhibit time-progression similar to that observed along the Yellowstone hotspot track, whereas this time progression is generated simply by a deep-seated plume. We have conducted three-dimensional fluid dynamical simulations of both scenarios including the effects of plate motion, lithospheric extension, melt and depletion buoyancy. The presence of melt and depleted residuum are mapped into seismic velocities and can then be compared with one another and also with the seismic results. Preliminary results indicate that the two mechanisms may be difficult to distinguish on the basis of seismic structure, although the effect produced by a deep-seated plume can be stronger and more focused than that produced by melt-driven instability alone because additional thermal buoyancy supplied by the plume aids in pushing aside depleted residuum.
Hernlund John W.
Tackley Paul J.
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