Underlying the Ozark plateau is an ancient volcanic uplift. That vulcanism is the reason that there are hot springs in Hot Springs, and that the only diamond deposits of any note within the continental US are in Arkansas.
Perhaps a Magma intrusion is forming underneath Guy, and we will have a new non Cascadian volcano!
to Post 43
3.8-magnitude quake rattles Guy [Arkansas]
http://www.arkansasonline.com/news/2010/oct/11/38-magnitude-quake-rattles-guy/
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Earthquake disappears from Google Earth, in the Midwest 10/11/2010
http://www.youtube.com/watch?v=kUvT-WIam_M