An explosion at a coal mine northeast Wyoming was big enough to register on seismographs on the scale of
a small earthquake.
Some people in Gillette reported feeling the ground shake from 16 miles away.
The U.S. Geological Survey recorded the blast at 11:11 a.m. Tuesday. The blast happened in the area of Cloud Peak Energy's Cordero Rojo Mine southeast of Gillette and registered as large as a magnitude 4.5 earthquake.
Using explosives is a routine part of dirt and soil removal at the coal mines where the blast occurred but explosions that register with such force are rare.