1 research outputs found
Dynamical effects of subducting ridges: Insights from 3-D laboratory models
We model the subduction of buoyant ridges and plateaus to study their effect
on slab dynamics. Oceanic ridges parallel to the trench have a stronger effect
on the process of subduction because they simultaneously affect a longer trench
segment. Large buoyant slab segments sink more slowly into the asthenosphere,
and their subduction result in a diminution of the velocity of subduction of
the plate. We observe a steeping of the slab below those buoyant anomalies,
resulting in smaller radius of curvature of the slab, that augments the energy
dissipated in folding the plate and further diminishes the velocity of
subduction. When the 3D geometry of a buoyant plateau is modelled, the dip of
the slab above the plateau decreases, as a result of the larger velocity of
subduction of the dense "normal" oceanic plate on both sides of the plateau.
Such a perturbation of the dip of the slab maintains long time after the
plateau has been entirely incorporated into the subduction zone. We compare
experiments with the present-day subduction zone below South America.
Experiments suggest that a modest ridge perpendicular to the trench such as the
present-day Juan Fernandez ridge is not buoyant enough to modify the slab
geometry. Already subducted buoyant anomalies within the oceanic plate, in
contrast, may be responsible for some aspects of the present-day geometry of
the Nazca slab at depth