What the heck is going on here?

The video appears to have first hit YouTube in early November and has been making its rounds on social media. There have been a lot of guesses as to what it is, ranging from a flowing sand dune to a river of quicksand.

The answer? Hail.

When you get enough of it, it can flow like a river, picking up loose dirt or sand along the way. It happened in Colorado a few years ago and in the Texas Panhandle in 2012.

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Natural Resources Defense Council