
A Gurgling Mud Pool Creeps Across So California Like a Geologic Poltergeist - HillaryBriss
https://www.livescience.com/63998-mud-pool-creeping-across-california.html
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HillaryBriss
_...the spring is acting like a moving sinkhole, with mud about 40 feet (12 m)
deep. As it moves through the region 's mudstone (a soft, sedimentary rock),
it leaves behind a sunken trail..._

