You may have seen the Youtube video giving the natural history of the fascinating ice flows that move down Yosemite Creek.

If not, here it is. It was produced by a fine photo artist, Steven M. Bumgardner.

Frazil ice is a harbinger of spring in Yosemite National Park, according to rangers and naturalists. It appears in March and April, forming as water from Yosemite Creek freezes on its plunge down spectacular Yosemite Falls.

As naturalist Pete Devine and ranger Victoria Mates say in the video, this is a phenomenon that goes unseen by visitors who show up only in summer.

If you get the chance, you might try to catch it this year. It is an amazing sight, but there is one caution: Don't try to walk on the ice. You could plunge straight through to the cold, cold water below.