The Canadian Avalanche Association describes a Size 1 avalanche as relatively harmless to people with a mass of 10 tonnes, a run of 10 metres and a force of 10 kilopascals. The CAA describes a Size 2 avalanche as on that could "bury, injure or kill a person". Typically with a mass of 100 tonnes, a run of 100 metres and a force of 10 kilopascals.
If you look at the top of the picture, you can see the crown of the slide just under the trees. I am standing at the bottom of the debris field. I'm going to call this a 1.5...
The above image is the result of a slide I kicked of while skiing in the West Bowl of Mt. Cain last Saturday. The decisions I made leading up to this are a classic example of what happens when the powder is beckoning...
My Saturday started out pretty early with shovel crew. This is a volunteer gig at Mt. Cain where you get towed up by the snow-cat at 7:30 am to shovel off part of the upper tee line before the mountain opens. While it is often pretty hard work the reward is one run before lifts open and then the advantage of being on the upper tee right at 9:30 am when everyone else is just boarding the lower tee. Usually you can get 2-3 laps in before there is a line up at the upper tee. On a powder day this pretty damn awesome!
Saturday was a typical west coast powder day. 24 hours prior it had been around or just above zero right to the summit resulting in significant amounts of heavy snow and rain. 12 hours prior temperatures had dropped and it kept snowing. It was also windy. This resulted in 25-30 cm of light fluffy powder, with some wind loaded areas sitting on denser wetter snow. Good for skiing on but also good for avalanches.
I spent most of the morning in bounds, but around lunch decided to head out to dig a pit to see just how reactive the light storm snow on the surface was. I was supposed to meet up with my friend Dougal to do this, and then the run I wanted to try if it didn't look to dicey was a safe line across the plateau in the bowl and down the main draw - a conservative line that slides relatively rarely. I was just about done digging and ready to cut some blocks to test the wind slab, when a guy I have toured with and two I hadn't showed up looking like they were going to ski the bowl. The guy I know, Todd, is very experienced in the area and I've toured with him a couple of times before, so I felt somewhat comfortable jumping in with him. Keep in mind visibility isn't very good and while I hadn't made anything really slab off in bounds, I had a feeling things were pretty reactive. The bulletin was also saying that the risk was "Considerable" - meaning "Natural avalanches possible. Human triggered avalanches probable." They sure had that right.
I caught up with them at their first safe spot, thinking they had heard me ask to tag along. They hadn't and appeared a bit perturbed that I was there, but at that point they were stuck with me. I made sure I insisted on tail gunning and we started to leapfrog down. We were heading into an area of the bowl called "Sliders". It's called that for a reason - it slides.
We made it down to the last pitch without incident, and I moved to a safe spot where I could see everyone get down. Marty headed to the left and wound his way down amongst some rocks and trees - no slides. Robin headed almost straight down the last pitch (you can see his tracks in the photo) with no problems and was waiting in a safe spot below. Todd went down to the right, and while I couldn't see it he triggered a slab on that side of the run. He skied out of it and I saw him waiting down below. So far, I had made some good decisions - digging a pit, going last, waiting for everyone to get clear, watching them ski. I had also made some bad decisions - not finishing my pit so I fully understood the snow pack and jumping in with a group at the last minute without really asking them or making a plan. Those bad decisions were about to catch up with me.
I was standing on a little knoll at the top of the last pitch looking to the left. I dropped in and cut across Robin's tracks heading to the untouched snow on the right side of the slope (lookers left in the photo). Immediately, I felt and saw the snow slab off and start to slide. I wasn't too worried as I have skied in slough before, and managed to get ahead of the slide and was sure I would be able to ski away from it. However, on my next turn it seemed like the whole pitch went with slabs coming off above and below me. I started to feel the snow grab at my skis and drag me down and it was everything I could do to hop off it and cling to the slope. I yelled "Slide slide slide" and sat down on the now exposed wind crust and watched it run out. Fortunately, as I had made one good decision in making sure everyone else was down and in safe spots it didn't come near anyone.
I am generally a cautious skier and wouldn't normally go anywhere near sliders with conditions the way they were. So, why did I go? I wanted powder. The temptation of light fluffy snow got the better of me and as an end result I could have been pretty badly hurt. I got very lucky.
Later in the day I headed out again, but with a different group skiing a much more conservative line. In this group was my friend Trevor who got caught in a slide last season and lost a ski - I almost immediately noticed that he was much more cautious in his approach and as a group we were discussing the lines, the snow pack and areas that could slide in a lot more detail. I tail gunned again and I have to say I have never skied more conservatively in my life especially as we were skiing a conservative line to begin with.
We had a great run, and at the bottom I ducked off to get the picture at the top of this post. The slide I triggered was pretty big and I am very lucky I was able to get out of it. Very lucky.
Let my bad decisions be a warning and lesson to everyone else. If you think its dangerous, it is. If you have made a plan in your head, stick with it and never dive into the back country without discussing the plan with your group.