QT Yellowstone Caldera (the eruptions of which can be violent enough to send a layer of ash six feet deep as far away as Chicago and which erupts every 600,000 or so years and last erupted 640,000 years ago) update

The Yellowstone monthly earthquake count almost quintupled in September to 158.
Scientists assured us that the seismic activity remains at “background levels.”
They did not say background to what.

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