The boundary between the Earth’s outermost layer, the crust, and the underlying mantle is speckled with mysterious, blob-like regions. Scientists have long known about these odd pockets, which are called ultralow-velocity zones. They slow down the seismic waves caused by earthquakes and may be the culprit for deep mantle plumes, which can lead to volcanic hotspots like those that created Yellowstone National Park or the Hawai’ian Islands.
Researchers have postulated a number of explanations for what these ultralow-velocity zones are made of and how they’re formed. But none of those ideas quite fit the data, especially given how differently some of the zones behave from one another.
Now, a team of scientists is proposing a new model that includes not only a feasible composition but also a plausible origin story for ultralow-velocity zones. Even so, the scientists behind the study concede that there could be different or even individual variations for other types of these mysterious, subterranean regions beyond their new findings.
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