Now that's cool.
The demise of a plate. We've never known just how deep they can go, how long a chunck of oceanic crust can last after being subducted. Some are thought to ride under the continental crust for quite a ways, even to the point of fusing to the bottom of a continent. Others dive steeply into the mantle. That a slab would go this deep also has implications to the circulation models of the mantle.