Dynamite blasts divulge runny layer roughly 100 kilometers below surface
Using ricocheted vibrations from dynamite blasts, researchers have glimpsed a layer of gooey material sandwiched between the Pacific tectonic plate and the underlying mantle. If present beneath all plates, the layer of partially melted rock could help explain how tectonic plates slide around Earth’s surface so easily, the researchers report in the Feb. 5 Nature.
“A weak, slippery base essentially decouples the plate from the sticky, underlying mantle,” says lead author Tim Stern, a geophysicist at Victoria University of Wellington in New Zealand. “This gives us a good idea about the forces required to push and pull the plates around.”
Earth’s outermost shell is a fragmented jigsaw puzzle of rocky plates sliding over the mantle below. The bottoms of these plates can be hundreds of kilometers underground, making them much too thick to drill through. Geophysicists