This is a photo of a landslide. But it's not a landslide that happened, it's a landslide in progress. Very, very slow progress. At Snake River Canyon, Wyoming, this flow of dirt is moving down a hillside and across a highway at a rate of 50 centimeters per hour, says Dave Petley on the American Geophysical Union's Landslide blog.
The Snake River Canyon landslide is slow enough that Wyoming Department of Transportation workers can climb around on it, as it's moving. In fact, they took a video of themselves doing this. When the film is sped up, you can see the landslide in action—and see that it is actually two separate landslides moving alongside each other! You also get a delightful sequence of fast-moving DOT workers that's just waiting to be paired with Yackety Sax.
Maggie Koerth-Baker is the science editor at BoingBoing.net. She writes a monthly column for The New York Times Magazine and is the author of Before the Lights Go Out, a book about electricity, infrastructure, and the future of energy. You can find Maggie on Twitter and Facebook.