Slab gap hypothesis

In geology, the slab gap hypothesis is one of the explanations put forward to explain several instances of extension that have seemingly paradoxically occurred near subduction zones (which typically compact crust).

The hypothesis is that when the spreading zone (the divergent plate boundary) of an oceanic plate is subducted under continental lithosphere[?], then a gap between the two now subducting chucks of oceanic lithosphere[?] forms. Since divergent plate boundaries are fed by mantle plumes[?] the hypothesis is that the mantle plume (which is far larger than a mere hot spot) exploits this gap and causes the overlying continental lithosphere (and the continental crust[?] on top of it) to spread apart.

This idea has been used to explain the extension and very large flood basalts[?] that occurred in what is now southern Washington, Oregon and northern California about 17 million years ago (see Columbia River Plateau[?]). Slab gap has also been used to help explain the earlier creation of the Basin and Range Province.