12:45 PM EDT, July 10, 2012
I agree with many of Mike Tidwell's suggestions about extreme weather ("Going to Extremes: Intense energy extraction is fueling climate change-linked bizarre weather events," July 6). More and more evidence indicates that the earth's climate is changing, and most of us scientists think that we humans are the major cause.
I am concerned, though, with the way Mr. Tidwell meandered off-message into a critique of hydraulic fracturing. He asserts that burning natural gas is only marginally better than burning coal. This may be, but coal releases more CO2, and it also produces other pollutants. But his linking of fracking with "an astonishing rise in earthquakes all across the mid-section of America" is extreme.
According to a June 15 U.S. National Research Council report, fracking itself does not pose a high risk for felt seismic events. An article from the American Geophysical Union reports that while 35,000 shale gas wells have been fracked in the U.S., only one case of felt seismicity is even suspected. Globally, there was one confirmed case — a small magnitude-2.3 quake — in the U.K. in 2011. Thus, in regions of low historically felt seismicity (including Mountain Maryland) the NRC report suggests that fracking poses little seismic risk.
Slightly more risky, though, is deep injection of used fracking fluids and other wastewater. Few people realize that there are over 150,000 wastewater injection wells in the U.S. (but none in Maryland). Earthquakes have been linked to wastewater injection, especially in areas of known historical seismicity. Other more troublesome risks of wastewater injection include the possibility of surface spills and well failures, so this practice clearly needs to be monitored and regulated with utmost attention.
David A. Vanko, Towson
The writer is a geologist and dean of the Jess and Mildred Fisher College of Science and Mathematics at Towson University.
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