PLANET EARTH
Weird blobs near Earth’s core may have been dragged from the surface
WORDS STEPHANIE PAPPAS
Strange ‘blobs’ deep in Earth’s middle layer may be chunks of ancient continental crust that have been dragged down by tectonic forces. These blobs, known as ultra-low velocity zones (ULVZs), have long puzzled scientists. They’re deep in the mantle, near the boundary with Earth’s core, so researchers can only glimpse them by studying earthquake waves as they reverberate around the planet’s interior. These waves slow down significantly in the blob regions, which indicates they are different from the mantle around them. In a new study, researchers suggest that these regions might be more widespread than previously believed, and that composition varies dramatically from blob to blob. “There’s more of that material down there,” said Samantha Hansen, a geologist at the University of Alabama. “Whatever that material is.”