When you see a road sign that reads “Caution, Falling Rocks,” what size rocks do you expect to see? Pebbles? Softballs? Bowling balls? Five-story buildings? If you answered the last, you must live in Arizona where a 50-foot tall, 30-foot wide, 500,000-pound slab is breaking away from a canyon wall and threatening to fall onto the power and water facilities for the Glen Canyon Dam. Oh, and on a road too. I wonder what that sign says. What’s worse, the rest of Arizona is breaking apart too and there are many reasons why.
The canyon wall is made of Navajo sandstone and is prone to cracking, but the U.S. Bureau of Reclamation says this is the biggest crack in years. It sent rappelers to scale the wall and drill bolts 6 to 8 feet into the sandstone. Unfortunately, pieces are breaking off despite the bolts. The only other alternative is to evacuate and hope it doesn’t damage the dam.
This is just the latest mysterious crack in Arizona. In March 2013, a fissure in Luepp became so big that it had to be fenced off. At the time the crack measured 900 feet long and 500 feet deep. The US Geological Service had no explanation for the crack and no predictions on how big or deep it could get.
There are many possible causes for the cracks and fissures breaking up Arizona. One is the removal of groundwater to support cities and towns. Giant fissures began occurring shortly after the state’s population began growing in the 1920s and leaving empty underground crevices where water once was.
Another possibility is mining and drilling. Abandoned mines can cause cracks and sinkholes, as seen recently in Russia. New oil and gas wells, especially those using fracking, can cause earthquakes and those are on the rise in Arizona. Then there’s climate change. Arizona has variations in elevation unlike any other state, so fluctuations in the climate are amplified here, causing both heat cracks and ice fissures. Many fissures, many possible causes, no one solution.
The Navajo Nation resides partially in Arizona and is the location of many of the cracks but even these ancient people can’t explain why so many are breaking apart the state.
Or maybe they can …