DENVER — Let’s get this out of the way: no, the Mile High City was not collectively celebrating 4/20 a week early on Saturday night.

There was, however, a big smoke ring in the sky that some people could spot all the way from Arvada. 9NEWS got about a dozen photos and videos of it, with lots of people making that same 4/20 joke. One person on Twitter even theorized it was a volcano.

The explanation for the smoke ring, though, is pretty straight forward.

It was the result of the pyrotechnics at the Supercross event at Mile High Stadium. The video below (which is from another event) shows how these large smoke rings come to be:

Check out a video of last night's smoke ring below: 

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