This convection is presented as whole mantle or whole asthenosphere
cells with hot material rising under the Earth's divergent plate boundaries and cooler material sinking at the convergent boundaries with the lithosphere dragged along by the horizontal flow of the asthenosphere
This important geodynamic change induced upwelling of asthenosphere
material, which led to adakitic magmatic activity and east-west extension.
These plates are not static, but move relative to each other at varying speeds, "gliding" over a viscous asthenosphere
. Exactly what mechanism or mechanisms are behind their movement is still debated, but are likely to include convection currents within the asthenosphere
and the forces generated at the boundaries between plates.
The archipelago is characterised by numerous contemporaneous volcanoes, some with plume magma sources, others from the asthenosphere
, possibly due to the young and thin oceanic crust.
This stage is accompanied by upwelling of the hotter asthenosphere
which worms up the lithosphere.
Therefore, quartz diorite might be formed in the post-collision extension environment after the collision of Lhasa block and Qiangtang block; lower crust delamination caused uplifting of asthenosphere
material, which further caused partial melting of lithospheric mantle and let basic melt mix with the acid melt.
It floats on a layer called the asthenosphere
- a silly putty like plastic material directly below it a few 100 miles in thickness.
Prograde metamorphism of the bounding thick crust may have led to formation of a dense, eclogitic lower crustal root that had detached from the more buoyant overlying granulitic crust and sank, together with its attached underlying lithospheric mantle, into the convecting asthenosphere
of the backarc region (see Krystopowicz and Currie 2013).
Although the lithosphere and asthenosphere
have to be distinguished by the viscosity, imaging the Earth's structure in terms of viscosity provides only weak resolution even with the most recent technology, (25) compared with seismic or electromagnetic imaging methods.
The dense crust would have dripped down into the mantle, triggering a return flow of mantle material from the asthenosphere
that would have melted to form new primary crust.
Francalanci, "Generation of oceanic-island basalt-type volcanism in the western Trans-Mexican volcanic belt by slab rollback, asthenosphere
infiltration, and variable flux melting," Geology, vol.