Earthquakes

There have been a series of earthquakes in mid-America in the last few years.  Although we do not think about it, this is not all that unusual.  History shows us that there have been many earthquakes in mid-America.  One of the most significant was the New Madrid earthquake http://www.dnr.mo.gov/geology/geosrv/geores/historymoeqs.htm 
http://en.wikipedia.org/wiki/1812_New_Madrid_earthquake.

The New Madrid earthquake created Lake Reelfoot http://www.reelfoot.com/.  I have camped at Lake Reelfoot.  That was neat!

But, I have to wonder.  The increased frequency of these earthquakes makes me wonder what is going on.  I have to wonder if oil industry processes have impacted the geological integrity of the area. It stands to reason.  If the oil industry is taking materials out of the ground, it is creating cavities underground.  When will these cavities become sufficiently large and numerous to cause the strength and integrity of the ground to disappear, and result in cave ins http://en.wikipedia.org/wiki/Cave-in, and maybe even earthquakes?