How Mantle Slabs Drive Plate Tectonics
Clinton P. Conrad,*
Carolina Lithgow-Bertelloni
The gravitational pull of subducted slabs is thought to drive the
motions of Earth's tectonic plates, but the coupling between slabs and
plates is not well established. If a slab is mechanically attached to a
subducting plate, it can exert a direct pull on the plate.
Alternatively, a detached slab may drive a plate by exciting flow in
the mantle that exerts a shear traction on the base of the plate. From
the geologic history of subduction, we estimated the relative
importance of "pull" versus "suction" for the present-day
plates. Observed plate motions are best predicted if slabs in the upper
mantle are attached to plates and generate slab pull forces that
account for about half of the total driving force on plates. Slabs in
the lower mantle are supported by viscous mantle forces and drive
plates through slab suction.
Department of Geological Sciences, University of Michigan, Ann
Arbor, MI 48109, USA.
*
To whom correspondence should be addressed. E-mail:
cpconrad{at}umich.edu
