There is a hotspot track cross-cutting the New Madrid Fault Lines!
And it may explain the upstick in recent intraplate earthquakes across the eastern United States!
At present, most hotspot tracks are observed on oceanic or thin continental lithosphere.
For old, thick continental lithosphere, such as the eastern United States, hotspot tracks are mainly inferred from sporadic diamondiferous kimberlites putatively sourced from the deep mantle.
As shown in the above figure, scientists have discovered an unexpected linear seismic anomaly in the lower lithosphere.
The unexpected scar in the lower part of the crus has both a reduced P-wave velocity and high attenuation and thus has been interpreted as a hotspot track.
The anomaly extends eastwards, from Missouri to Virginia, cross-cutting the New Madrid rift system, and then bends northwards across a 75-million-year-old diamond-bearing formation in Kentucky.
There is no sign of the hotspot track on the surface.
The New Madrid rift system is responsible for some of the most powerful earthquakes in North American history and this newly discovered hotspot track could explain the late Mesozoic reactivation of the New Madrid rift system and the increased seismicity of the eastern United States. [Nature]