December 11 was a weird day at the Grand Canyon.

This image, captured by Maci MacPherson with the National Park Service, looks like some alien cloud world and definitely not arid Arizona, but in a rare weather display, low-lying clouds nearly filled the entire Grand Canyon. This event is actually supposed to be extremely rare. However, a similar phenomenon occurred last year in December as well. Only this time, the park service time lapsed this seemingly otherworldly event.

What makes this cloud-filled wonder possible is a process called inversion, where warm air on top of the Canyon traps cooler air down below, creating the visible cloudstew in the world's largest mixing bowl.

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What was described last year as a "once in a lifetime" event now seems to have given us all an encore. Grand Canyon, now you're just showing off. [NPR]

Images via Maci MacPherson/National Park Service