Okay so avalanches. I find this to be supremely fascinating, especially considering I never really grew up around mountains and this is all so new. So as the climbers from the last post explained, basically what happens is that snow falls on a mountain and when the sun comes out and starts warming the snow up (especially in the spring when it starts getting warmer), the snow starts to melt. At night when the temperature drops, the snow turns into ice which then begins to act more like ball-bearings. When the next layer of snow comes down, it sits on top of the slick snow and isn't embedded onto the actual slope of the mountain anymore. It's like a layer of a cake that can slide right down when it starts to shift around a bit. They tried climbing the rock face next to the shop and felt it start to slide down several times so they came off since it was too dangerous to continue.
So that said, check out the avalanche pictured here, or actually the aftermath of it. Look up at the top right and you'll see the fractures where the section of snow broke away from the rest of the sheet. It then started plowing its way down the mountain, leaving this path of snowy carnage down the slope. Note the difference between the smooth powder and the area where the avalanche went through. It all dumped down on the road, effectively blocking the whole thing down.
I'd asked the ranger how long it would take to clear an avalanche off the streets and he said typically 3-4 hours. A big dump would take the crew all day.