A hotspot track - a line of volcanic rocks that can stretch for thousands of kilometres across Earth’s rigid crust and mantle - could be hidden beneath the eastern United States, reports a study published online in Nature Geoscience. This track, potentially formed as the North American tectonic plate passed over a plume of upwelling hot mantle about 100 million years ago, could have triggered seismic activity and fault movements in the New Madrid rift system in the state of Missouri.
Hotspot tracks are difficult to identify on land because the continents are so thick. Risheng Chu and colleagues use seismic data to analyse the structure of the continental eastern United States. They identify a linear, east-west trending seismic anomaly within the continent that extends from Missouri to Virginia, yet find no obvious expression at the surface. The authors use computer modelling to show that the anomaly could have been formed by a plume of hot mantle that upwelled beneath the North American tectonic plate as the plate gradually drifted across it.