New Mexico Is Stretching, Slowly but Surely

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The Rio Grande Rift

The driving distance between Phoenix and Dallas is getting farther. It’s a minuscule difference – not even a millimeter a year – but it’s a tangible phenomenon, and you can blame on the middleman: New Mexico. The Rio Grande Rift, the fault line that bisects the southwestern state, is bursting at the seams, pushing apart New Mexico’s borders and stretching the land around it.

But don’t expect to straddle the fault line and have your legs ripped out from under you, unless you have centuries to wait:  the state is getting just one inch wider every 40 years. Scientists calculate the Rio Grande Rift’s pace of expansion as approximately 1.2 nanostrains per year. So it’s less an expanding waistline than a stretchmark. Still, it’s having an effect on hundreds of miles of surrounding terrain. According to the group of seven scientists from New Mexico, Colorado and Utah, who studied the Rio Grande Rift for more than four years before releasing their findings in the January 2012 issue of Geology Magazine, the pull of the canyon isn’t a localized problem.

(PHOTOS: Along the Rio Grande, Scenes of a Tense Border)

“We didn’t expect it to be so spread out,” University of Colorado geophysicist Anne Sheehan told the Albuquerque Journal. Indeed, the rift’s movement hasn’t been absorbed into the land directly around it, leading to a widespread stretching and rucking that has affected terrain in a radius of hundreds of miles – and maybe even more, stretching not just New Mexico but Texas and Arizona as well.

The research team calls it a “distributed deformation,” but we prefer to think of it as an America-shaped piece of taffy stretching endlessly, slowly but surely. And that should give you an idea of what will happen if this rifting phenomenon keeps occurring.  It’s hardly a visible effect, but it’s an unexpected feature of the ever-changing landscape. The scientists plan to continue monitoring the 25 GPS units they’ve set up in the region to see if the pace keeps up. They’re not yet sure if the rifting puts the geology of the region in peril. The stretching of the Earth’s surface is easier to see at the edges of tectonic plates, where there are typically volcanoes or mountains, but movement on an continental rift is more mysterious. Fortunately, at the paltry rate it’s happening, scientists will have centuries, if not millennia, to come up with a game plan for dealing with it.

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