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SUMMARY:Multi-Scale Dynamics and Rheology of Mantle Flow with Plates - Lau
 ra Alisic\, Cambridge
DTSTART:20121010T153000Z
DTEND:20121010T163000Z
UID:TALK39650@talks.cam.ac.uk
CONTACT:Gareth Roberts
DESCRIPTION:Fundamental issues in our understanding of plate and mantle dy
 namics remain unresolved\, including the rheology and state of stress of p
 lates and slabs\; the coupling between plates\, slabs and mantle\; and the
  flow around slabs. To address these questions\, models of global mantle f
 low with plates are computed using adaptive finite elements\, and compared
  to a variety of observational constraints. The dynamically consistent ins
 tantaneous models include a composite rheology with yielding\, and incorpo
 rate details of the thermal buoyancy field. Around plate boundaries\, the 
 local resolution is 1 km\, which allows us to study highly detailed featur
 es in a globally consistent framework. Models that best fit plateness crit
 eria and plate motion data have strong slabs with high stresses. We find a
  strong dependence of global plate motions\, trench rollback\, net rotatio
 n\, plateness\, and strain rate on the stress exponent in the nonlinear vi
 scosity\; the yield stress is found to be important only if it is smaller 
 than the ambient convective stress. Due to coupling between plates\, slabs
 \, and the surrounding mantle\, the presence of lower mantle anomalies aff
 ect plate motions. The flow in and around slabs\, microplate motion\, and 
 trench rollback are intimately linked to the amount of yielding in the sub
 ducting slab hinge\, slab morphology\, and the presence of high viscosity 
 structures in the lower mantle beneath the slab.
LOCATION:Marine/Wolfson Building lecture hall
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