NileGuide Expert Says:
A freaky show of natural power - you have to be lucky to get the right conditions for it to form.
NileGuide Expert tip:
The NPS frazil ice video has been a viral sensation. Seeing it on screen is much easier than seeing it in person.
Frazil ice is a very transient natural phenomenon, best seen on early mornings in April on Yosemite Creek below Yosemite Falls. It doesn't happen every day or even every year, but if you see frazil in action, you'll be astounded. A portion of the mist falling from Upper and Lower Yosemite Falls will freeze while it's falling during the sub-freezing note. These ice particles will then flow in the creek water, turning the stream into a big slushie/slurpy. It can move like white lava, building up to several feet in depth as it flows, stalling and surging as it advances downhill in different directions. It's dynamic and not always predictable; it can cover trails and bridges, so be careful. What may look like a linear snow patch may be a few inches of unconsolidated frazil deposit with 6 feet of rushing icewater beneath it.
You have to be lucky and be out early in the morning to see it flow. Deep deposits may remain for months, looking like old snowbanks. See the video on the park's website to get an idea of this strange feature.