Inner Earth processes and systems - Physical Processes in Earth and Environmental Sciences - page 235

processing enabled geophysicists to track the fate of
descending cool slab down to and often through the once
inviolate 660 km discontinuity. This was linked to the abil-
ity of seismologists also at this time to distinguish what was
interpreted as slab material at or about the core-mantle
boundary, a zone termed “D”. These developments sug-

gested that mantle plumes and therefore large-scale out-
bursts of intraplate continental magmatism might arise
from periodic “eruption” of molten slab at this boundary,
though there seems little evidence that core material itself
is involved in this process. It seems that Cybertectonica acts
from surface to core/mantle boundary.

(b)

(a)

core

core

(c)

Hawaii

Pacific Rise

core

Africa

Fig. 5.46 Models for plates, plumes, and mantle convection. (a) Whole mantle convection drives and recycles plates. (b) Two-tier system with
plate advection and lower mantle convection separate. (c) Upper level advection with deep slap penetration, periodic plume upwelling and
lower mantle convection.