This week my Skeptoid episode was about fracking, short for hydraulic fracturing, the controversial mining technique for deep natural gas deposits. The shock doc Gasland put fracking into the public eye, and not in a very complimentary way. Gasland blamed fracking for putting flammable methane into tap water, for mysterious illnesses caused by its “toxic” fluids, contaminating ground water with poisons, and killing animals, in addition to a host of political conspiracy charges. If you’re wondering why this decades-old practice did not seem to cause any problems before Gasland came out, it’s because Gasland was largely fictional. Most of its charges are based on real phenomena, but fracking itself rarely has anything to do with them. That’s not to say there are no environmental concerns about the practice. There are, to be sure; and the EPA is in the midst of a major study to find out how serious these concerns are. Some of these were discussed in my episode. One, in particular, I omitted: the question of whether fracking causes earthquakes.
It doesn’t sound entirely implausible. Some fracking operations extend for as long as kilometer horizontally through strata several kilometers underground, and add pressure in the same way a hydraulic ram works. It’s enough the actually crack the rock layer. These cracks are then filled with sand to hold them in place. It sounds like such huge pressures might well trigger an earthquake in a zone that already has some stress from natural gas extraction that has caused underground pressure changes.
And, in fact, fracking does unquestionably cause earthquakes: tiny ones. Every time a rock cracks underground, it’s a seismic event. When a kilometer of shale is fracked, that’s a lot of seismic events. But they’re really small, and don’t have anything to do with natural fault lines.
Here’s a quick explanation of why I didn’t cover this question in my episode. It was in my notes from the beginning, and a quick read of Wikipedia or other online sources is likely to confirm the connection between major quakes (larger than 3.0) and fracking. But as I did research and spoke with geologists, regulators, and people in the drilling industry, I quickly learned that it’s something nobody takes seriously. My experience was anecdotal, but to those in the know it’s something of an old joke. So, when my episode was running long (as most of them do), I had to cut something (as usual), and earthquakes were what I redlined from my notes. I assumed the claim was oddball enough that it wasn’t something real people were actually concerned about.
I was in error. Fracking and earthquakes was the subject of many tweets and emails I received. Why didn’t I go into this? What was I trying to cover up?
24 hours after my episode came out, I was faced with an entire screen full of email notifications that someone had cancelled a recurring donation to Skeptoid. The fracking episode had caused unprecedented anger among many listeners. I’m pleased to note that all the communications I’ve received from people who are knowledgeable about fracking, including people working in drilling, former anti-fracking activists, state and federal regulators, and geologists of several stripes, all told me that my episode was spot-on. However that’s small comfort for having driven away so many of my supporters.
Here is abbreviated coverage of my understanding of fracking and earthquakes, based on the small amount of research I’d done on it before cutting it out. Shale, which is the main kind of rock in which fracking is performed, is fragile. It splits easily. If a shale bed is under tectonic stress, it gives readily. Large tectonic pressures will not build up behind shale. Fracking the shale to break it up is unlikely to relieve any massive forces; as a pressure barrier, shale is a dog that won’t hunt. (I did limited research and have no personal expertise in this area, so I invite any and all corrections from the geologically proficient.)
The point of fracking is not to make the shale unstable, but rather to open it up in a stable way. All that sand does effectively hold the fractures open, as intended, and does not result in an unstable layer. It’s not like it will suddenly all collapse and cause an earthquake. Remember, we’re really deep underground, and the pressures holding everything in place are immense.
In lieu of discussing earthquakes in the episode, I put a really good newspaper article in my References & Further Reading section on the web site. If you’re interested in the earthquake question, you should read that article. But here’s a summary. There was a lot of concern that fracking had caused the August 23, 2011 earthquake in Virginia, which was a 5.8 — damn big and unusual for that region.
What has caused earthquakes in the past is not fracking, but a superficially similar practice: that of disposing of waste liquids in deep (really deep) drilling holes. If you drill one of these through a fault zone, you can (a) lubricate it, and also (b) put a lot of pressure down there. Things might go, and have, on occasion (this procedure is now required to undergo strict review by the EPA to make sure there are no faults around). But fracking is different. Fracking drills horizontally through natural gas containing shale, not through hard rock fault zones. But in some cases, used fracking fluid has been transported and disposed of in such wells, thus potentially causing an earthquake. That’s about as close as we can get to connecting fracking with earthquakes.
As far as this particular earthquake goes? I quote from the article:
For Virginia officials, the conclusive proof that drilling did not cause last month’s quake is that no well — for natural gas extraction or fluid waste — exists within at least 150 miles of the quake’s epicenter. Pressure would have had to cross at least two major thrust faults and several smaller ones to travel from Marcellus shale drilling in the Appalachian Basin and affect the Central Virginia seismic zone in the Piedmont, said David B. Spears, Virginia’s state geologist.
“There’s just no way any kind of drilling or hydrofracturing in those wells could be physically transmitted through the Earth over such a great distance. It’s just physically impossible,” Spears said. “With eighth-grade physical science you can figure this out. It’s just way, way, way too far and completely geologically isolated by multiple barriers.”
The Marcellus formation lies in one of the least seismic zones in the world, said Helen L. Delano, a senior geologic scientist in Pennsylvania’s Department of Conservation and Natural Resources. The risk for earthquakes is minimal, even without drilling.
I believe there are enough questions about fracking to justify a good documentary film that explores what we actually know and what we’re still learning. Too bad it won’t be made: sadly, Gasland has already poisoned that well.