Rime Ice Rivers: How many ways can water flow down a mountain?

Two years ago, I joined a couple of friends on a climbing trip to Mount Shasta. We failed to summit due to high early morning winds, and turned around at sunrise when we noticed no climbers above us were advancing to the windblown ridge. On the way down, we encountered incredibly beautiful rime ice rivers, coursing down the steepest part of the route, pushed by the incessant downslope wind.

Rime ice coating the rocks the day before.

There were so many incredible things about that morning, I forget to tell people about the magical rivers of rime. I usually tell the story of how intense and insane it was to be very sleepy, standing on the steepest part of the route, in the dark between moonset and dawn, and have gusty winds blast hard chunks of snow into you at high speeds. It was fairly mellow while the moon was still up, and I would close my eyes and take 30-second naps every time I stopped. But after it got dark, it felt like the mountain was taking advantage of the darkness, trying to knock us off the route. Often we couldn't easily identify our climbing partners among all the climbers. In between gusts we could make upward progress, but when you heard the gusts approaching, you had to dig in your crampons, lean your helmet over your ice axe, and brace yourself while the wind and snow pummeled you. It would stop, and you would straighten up and take a few more steps until the next gust. In the dark. At one point I thought for a few terrifying seconds that a companion had tumbled down the mountain, but he had just moved across the slope below me to my other side.

It was insane.

But there I go again, not getting to the amazing rime ice rivers. I won't spend a lot of words describing them. Here they are--see (and hear!) them for yourself in several very short videos.

So how windy was it? When we got back to our tents, it was clearly very windy compared to what a tent is able to withstand: