The Wilson Cycle, the repeated opening and closing of oceans, commonly
along roughly the same lines, is here attributed to the presence of e
clogite-facies roots of partially collapsed orogens. We present a fini
te-element thermal model that suggests that such roots will weaken the
orogenic lithosphere relative to that of the adjacent foreland for hu
ndreds of millions of years and make it a preferred sire for later rif
ting.