"A lithospheric drip is a geological phenomenon in which a heavy rock formation sinks in a lighter rock formation, the latter having been made plastic by high temperature and pressure.  A long trail is left behind the heavy material, like honey dripping off a spoon.  A lithospheric drip has been discovered below the Great Basin in Nevada." 

Mr West's team thinks the "drip" started some 15 million to 20 million years ago but only detached from the overlying plate recently. 

Okay, so what does that mean it will do now?  My memory of honey dripping off a spoon is that 1) the honey falls and 2) There's air where the honey was.  If the surrounding area isn't sinking, does that mean it's only a "thin" plate on top of a gaping hole where the blob used to be?