Beneath the American Midwest, on the continent of North America, the underside of Earth's crust is dripping into the planetary interior. There, blobs of molten rock are coalescing in the upper mantle of the planet, eventually gaining enough mass to precipitate deeper, a slow, gradual mechanism revealed through seismic monitoring that shows the thinning lithosphere underlying the region. It's nothing to worry about. Only recently discovered, lithospheric dripping occurs in other parts of the world, too – but the revelation opens a new window onto our dynamic Earth's unique geological processes. "This sort of thing is important if we want…