This body—the "Farallon Plate"—was once one of the three ... that are weakening the base of the crust. A map of the North American craton—outlined in black—as revealed by seismic velocity ...

The Farallon slab, a sunken tectonic plate, appears to be the cause, influencing mantle flow and weakening the craton's base ... researchers created a detailed map of what lies beneath the ...

researchers created a detailed map of what lies beneath the central United States. What they saw were large, drip-like structures extending from the base of the craton into the mantle transition ...