Jess and I decided to try snowcaving a little while ago.
Snowcaving is the activity of digging a cave, in the snow, and sleeping in it. Snowcaves are most often used as a survival technique for mountaineering. The idea is simple. Snow is a very good insulator. So good in fact that a well built snow-cave will almost always end up right around freezing (32F, 0C), basically regardless of outside temps. This is because if it gets any warmer, the snow melts. So, if it's much colder than that outside building a snowcave can be a huge win, and a way to survive.
It turns out to be a slightly complex process though, so it's not something you want to try for the first time when it *has* to work. So, Jess and I decided to take a trip up to Tahoe, and give it a try. Jess had talked to some people before about how to build a snowcave, and we both read a book she gave me a while back written by the Mountaineering club in Seattle (overly opinionated and single-thinking, but they do know what they are talking about). This was the bulk of our preparation.
We were feeling pretty paranoid. We rented a large vehicle with 4wd that we could sleep in if required. We brought our 10F sleepingbags, and spare sleepingbags to leave in the car (my spare was 40F, but oh well). We also left a bit of spare clothing in the car (Jess left a complete down ski-suit). Additionally as backup we had a HAM radio that... umm... honestly I really should relearn how to use.
Warm gear I used:
10F FF sleepingbag
3/4" ultra-dense closed cell foam pad
3/4 length ultralight thermarest (older square model)
2 pair mountaineering smartwools
1 pair super-heavy REI brand wool socks
1 pair thinner smartwools
Winter weight underarmer running tights
pertex qantum pants
wool smartool t-shirt
wool smartwool midweight shirt
fake-poofy-stuff insulated parka
"waterproof"-breathable rainjacket (not quite waterproof, but close)
insulated gore-tex ski-gloves
smartwool glove liners
oversized lightly insulated waterproof hiking boots
Other gear we brought:
whisperlight whitegas stove (we brought alcohol as well, to test melting snow with)
collapsable aluminum avalanche shovel
70" black diamond ice-axe
Leki hiking poles with mud-baskets swapped for snow-baskets
In other words, I threw everything warm I had into my backpack, and grabbed everything that looked useful for "snow". Jess basically did the same thing - but she owns more warm gear than I do :).
Jess had been pushing hard that week on work, and to prepare for the trip. So, she was feeling sick from pure exhaustion. After much consideration we decied to do it anyway. So, we left for tahoe on friday, after getting quite tired and discovering where *not* to try and sleep in your car on the road we slept the rest of the night in a wallmart parking lot. She felt better the next day, though not fully recovered.
Next day we drove up to kirkwood and rented the snowshoes. Jess picked up ski-boots as well, because she was worried about her newly waxed all-leather boots. We'd looked a bit before hand, but the lady there confirmed that avalanche danger was fairly low. We then backtracked to a sign that had said "8000 ft" that looked like it had about 6 feet of snow around it. There was a pulloff there and some trails leading off. Also, being at basically the top of the mountain, it seemed like a good place to start searching without worrying about avalanches.
So, after quite a while of changing clothes and such, we tromped off into the woods. Not far in (thus giving us the ability to bail in an emergency) we saw a nice hill that looked promising. So, after staring at it for a bit we found a good spot to start digging. By this time we had maybe an hour until dark.
So, here's a quick overview of how a snowcave works (please don't use this as a guide, go read a book by someone who knows this stuff). The question is, how do you keep heat in the snowcave? Well, heat rises right? Basically, you find a hill and you dig down and in. Once you have a tunnel a little ways in, you start digging upwards. The goal is to get a platform that is entirely above the entrance, so that heat will pool up in that space, and not leak out the entrance. If the snow is right, you can cut blocks of snow out to block off the top of the entrance, reducing the amount of digging that has to be done, and you can block the bottom part of with a backpack as sort of a "door".
For obvious reasons you want the shelter to be as small as is comfortable, so there's less space to heat. You need airholes so you can breath, so you drill some in the roof so you get flow-through ventilation like groundhogs due - because the hole in the roof, and the unblocked bit of the door are at slightly different elevations the pressure differential will slowly push air through (not a ton, but enough). As a last and exciting constraint, you want to stay *dry* in what is, fundamentally... a whole lot of frozen water, which you are about to heat up. To do you this you smooth the roof as much as you can, so it drips down the walls rather than on you, and you make it large enough that you don't touch the sides and can dig a trench around you to collect the water and funnel it elsewhere.
So, we set about digging this shelter. The digging went fine, we started by digging downwards, being worried that we might end up going through the roof. We also stuck 1-foot long sticks in the ceiling, if you hit these while digging, you stop digging upwards so you don't collapse the roof. We had one shovel, so we took turns. Whoever was shoveling had cold knees, but was otherwise warm, whoever wasn't was just cold. We only used the shovel for digging. We discovered that having a collapsable handle was very useful for digging in such a tight space.
The digging process takes a LONG time, I think we were digging until near midnight. 2 shovels would speed it up, but not by twice. As it cooled off, and we got deeper into the hill it became obvious how much warmer it was in there. My pertex pants were completely soaked. Every time I went in they melted, when I came out they froze solid (note that this means my tights were just soaked). I was very paranoid about the roof depth, because I wanted to sleep that night. When we were finally nearing completion we attempted to punch a hole in the ceiling. We tried the poles, first. After a lot of fiddling we managed to get the entire length of a hiking pole in... without seeing it on the other side. It turned out that we had about a 5 foot thick ceiling! The snow where we'd dug is was MUCH deeper than needed. Well, I ended up going on the roof and shoveling down about 3 feet, then we used the handle of the ice-axe to actually poke the hole.
About now Jess simply maxed out, she ran out of energy and was completely exhuasted. We were just about to do dinner and I'd grabbed some of my stuff and thrown it in the shelter, so she took a quick nap in my sleepingbag while I cooked up some dinner on the whitegas stove (after melting some snow to do so).
To melt snow I used a trick a friend of ours explained to me. The trick with melting snow is to do a little at a time, water transfers heat wonderfully, snow doesn't... so melt the snow in water. If you have some water, prime the pot with it. Now, put some snow in it, so it's kinda slushy, but still nice and wet. Heat it up until it's not slushy anymore, add more snow, repeat until you get the amount you want, then heat that up. It should be noted that melting snow takes a LOT of energy, phase transitions are expensive (I'll probably write an article on this later).
In any case, I made up some hot Jello first, which tasted amazing, then I made dinner and we ate up and crawled into bed. Digging in the awkward space had used an enormous amount of midriff muscle, along with strange shoulder muscles and the like. We were also quite wet, I especially was soaking wet.
For the period of dinner, and getting in my sleepingbag had remained unpacked, and had gotten slightly damp. My tights were much wetter than a realized (given that my pertex pants were soaked this shouldn't be surprising, but I was exhausted, intelligence kinda goes out the window). So... I soaked my down sleepingbag.
We slept okay. The walls and floor of the cave quickly turn to ice. Jess' pads didn't supply sufficient protection, so she bruised her hip during the night. She also couldn't feel her toes for most of the night. I have very good circulation, so despite a wet bag, I slept okay due to having a lot of upper-body insulation (the parka, and the wool shirt) as well as my hat. I also wore a dry pair of socks.
Oddly, it was *still* good enough that Jess felt better the next morning than she had all week :P. We did it, and it worked. If I was expecting this to keep me safe I'd do a few things differently though.
1) wear waterproof pants, that was by far my biggest problem
2) bring a waterproof bivy-sack, this just makes it harder to screw yourself over, and gives you a good backup plan
I'm amazed though, apparently it dropped to about 9F, that should've happened while we were asleep, but it probably got close to that while we were digging. I was soaking wet in my pants and tights, and was still okay (not great, but no permanent damage I can tell). That is really impressive for those tights!
Jess had a full thick wool outfit, thick pants, thick shirt. As a result she didn't have problems with the damp and cold excepting for her feet. I had waterproof boots that were oversized (this is *really* important, it lets your toes flex), she had undersized ski-boots that didn't fit right (turns out she would've been better off in her leather bots - we know now).
The next morning we spent quite a while dismantling the cave. The 5 to 6 foot thick roof wouldn't just collapse, we had to dig it out with the ax and shovel, which made for quite a project.
We then went snowshoeing that day in the beautiful warm sun. The snowshoes were so-so (all plastic, so very loud, and they were too small, not enough flotation for off-trail). We had a great time running up and down hills, and wandering aimlessly across a lake a few miles. Then drove home.
All in all a HUGE success! we came back with all our limbs and digits, no permanent damage, and learned a LOT, and we even had fun doing it.
Note - please don't take what we do to imply it's safe. 1) Jess has SAR training, where you walk down rivers in below freezing weather for multiple days. 2) we've both slept at 15F or so before, and with worse gear 3) even still it seemed rather plausible that one of us would leave with frostbite and maybe missing digits on this trip.
I encourage you to adventure, but please keep it within your limits (which may well be farther out than you expect). Push your limits one step at a time, and any time you do so intentionally make sure you have a fallback. Don't treat our blog like we know what we're doing, we don't, so don't believe us :P.