Staying outside overnight in a snow cave to wait out a blizzard doesn’t exactly sound like it would be a comfortable experience, but being able to build an effective survival shelter in such conditions can be a lifesaver. Snow is an insulating material, so if you construct a cave shelter out of snow, you can rest protected from the elements within a space that will grow warmer as your body radiates heat.
Building a snow cave will require time and effort, but if the alternative risks include death by exposure, then it’s well worth the energy expenditure.
In order to build an effective snow cave, a good backcountry snow shovel will help immensely. Look for a lightweight but sturdy shovel that has a collapsible handle and can fit easily into your backpack. An aluminum shovel should be one item you carry as part of your essential avalanche gear kit, but if you are planning on hiking, snowshoeing, skiing, or winter backpacking, it can come in handy even in areas that that lack avalanche danger.
If you need to build a snow cave but you do not have a shovel, then survey your gear and surroundings and look for something from which you can fashion an improvised shovel, such as a backpack or a flat piece of wood.
Look for a steep snow slope--around 30 degrees--that is covered with several feet of snow. Since you will burrow into the slope, the snow needs to be at least a foot deeper than you are tall if you plan to lie down inside of the cave. Choose an area covered in dense snow, as light or non-consolidated snow will not form a solid roof or walls within which you can shelter. Choose to build the cave in an area free of trees since snow may dump unexpectedly from branches and collapse the roof of your shelter.
Snow Cave Construction:
Begin burrowing directly into the snow slope in front of you by hollowing out a tunnel that’s as wide as your body but only about five feet tall. Once you’re deepened the tunnel by a few feet, begin excavating the snow from around you to make a waist-high platform. Then widen the space above you and all around. Continue hollowing out the space in all directions except downward, opening up the cave so that its ground level sits about a half a foot above the initial entrance hole.
Continue hollowing out the space, but be careful to leave about two feet of snow above for a solid roof. A smaller cave will be warmer than a larger cave, so only dig out as much space as you will need to sit and sleep comfortably.
Pack down and smooth out the sides of the cave and the ceiling. Be especially careful to smooth out the ceiling of the cave since any protrusions will cause water to collect and drip. If the ceiling is smooth, then condensation will run more easily down the sides of the cave’s walls instead of dripping on you or your gear in the cave’s center. Create a small ditch around the edges of the walls to keep any melted water from pooling in the center of the cave.
Create a few ventilation holes in the roof with a trekking pole to prevent accumulation of carbon monoxide within the cave, but be careful not to damage the integrity of the structure while doing so. Finally, create a door by putting a backpack or a snow block at the entrance, but leave some space for ventilation here as well.
- Sit or sleep on a sleeping pad, an emergency blanket, or on your backpack to prevent loss of body heat while you are inside of a snow cave.
- Avoid cooking inside of a snow cave to prevent asphyxiation, and check vent holes regularly to make sure that you are getting adequate oxygen and gas exchange.
- Create a dome-shaped ceiling for the best support and best chance of avoiding drips.
- Use snow blocks to extend the entryway and to make the entrance more windproof.
- Customize the interior as you wish, but don’t get too comfortable, as your survival shelter is only a temporary stopping point on the way to safety.
- Collapse the snow cave when you vacate it so that unsuspecting hikers and skiers don’t fall through the roof.