I haven't done this a lot but I can say building one with my friends one time on Mt. Shasta likely saved our lives in a white out blizzard that dropped 5 feet of powder snow on us without access to a good shelter. Someone might say, "Why didn't you just go back to your car?" The answer would be, "We could not see more than a foot in front of us because of the white out and blizzard and we didn't have a compass and since it was the winter of 1970 no one had mobile GPS devices or cell phones yet. So, a Christmas vacation lark on Mt. Shasta turned into a survival experience that many would not have lived through. So, since one of my friends who was attending Sacramento State University had attended a Snow Cave building seminar recently, he knew what to do and his knowledge saved the three of us.
When we found our tracks and that we had walked a big circle with our snow shoes and backpacks on we realized we were in danger. (Remember none of us were more than 22 at the time so we were still in male fearless mode most of the time). However, young male fearless mode doesn't necessarily keep you alive all the time. We realized a real adventure had begun and the question was would we survive it?
So, since the snow was deep in drifts above 5 and up to 10 feet deep in drifts up against hills where there were trees we took off our snow shoes and began to dig ourselves a survival shelter somewhere between the main parking lot at Bunny Flats on Everitt Memorial Hiway on Mt. Shasta and the Sierra Club Survival Shelter which had been our goal until we realized we were in danger because of the severe whiteout and blizzard. So, we used our snowshoes as shovels to dig our survival shelter according to our friend who had just taken a seminar on doing this at Sacramento State University. Since I tend to have some problems a little with claustrophobia since having whooping cough and childhood epilepsy I got to be nearest to the entrance of the snow cave. So, entering the snow cave for me was a little like going into a tomb that I didn't know if I was coming back from or not. During the night the snow melted into all our sleeping bags so when we woke up in the morning (we didn't really sleep because our teeth were chattering too much). And after that I found I was going into what I might call almost convulsive shaking. The person the warmest was in the middle but got his legs bent backwards because we were all trying to stay warm enough to survive the night, so he had some problems with his knees from this the next day. Luckily, during the night the storm ended and the whiteout had ended too. However, since 3 or 4 new feet of powder had come down I started to panic as I dug us out of the cave that had sealed itself off with new fallen snow because I hadn't considered the potential fact that the old entrance to our snow cave was now covered with 4 new feet of snow. We were lucky we didn't die without an air hole out of the cave to the outside.
But probably our breaths helped keep us warm and we were too cold to pass out and never wake up which is what literally happens to some people in snow or ice caves when they seal themselves completely off for the night from the outside world. I suppose if it isn't snowing a blizzard like we were experiencing at the time making a vertical hole about fist size through the ceiling should vent enough CO2 and allow enough oxygen in during most nights in the snow. After we got out of our Snow Cave our pants were wet from melting snow. Luckily, we didn't freeze to death because the temperature was around 20 degrees so our pants ( Blue Levi jeans) froze solid except for the knees. So, we were cold but the dead air space around our legs kept us from freezing to death. However, so much snow had fallen that even snow shoes were not very effective. Once we put on our packs to return to my 1966 VW Bug as we wanted to stay alive. But since 3 to 4 feet of powder had fallen we couldn't easily use snow shoes without falling into the snow sideways with our packs on. So, we finally realized that we had to take turns leading and each step in the snow had to be packed down three or 4 times in order to not fall down in the snow. If one of us fell down the other two had to place themselves strategically on both sides to pull the one that fell up on top of the snow that was 7 feet or more high with the top 5 feet that was now powder. Eventually, we made it down to Everette Memorial Hwy. However, because the snow had drifted so much none of us were sure if it was the road or not because there was now over 12 to 15 foot drifts on it. So, one of us dug down with our snow shoes and finally found the asphalt road so we knew where we were. But when we walked up to my Bug all I could see was was the top three inches of the aerial for the radio and the rest of the Bug was buried in the snow. So, again we were stuck miles away from any civilization. But then, in the distance we heard one of the big snow blowers that was headed towards the old Ski lift up past Panther Meadows at that time. (That ski lift since then was destroyed by a snow avalanche) and the new one is reached from hiway 89 now. The new one is the Mt. Shasta Ski Park but it is now closed for the season. I have skied there many times with my friends and enjoy it as well as metal edged cross country and mountaineering skiing on Mt. Shasta from Bunny Flats to 7 mile Curve. Also, I have skied up to the Sierra Club survival lodge and often it is completely covered over with about 20 to 40 feet of snow during the winter and spring.
Two other important things to consider before building an ice or snow cave is that the snow has to be cohesive enough not to cave the snow in on you. Another useful thing to know is under no circumstances can the interior of the snow cave go above 50 degrees Fahrenheit or the whole thing begins to melt down upon you. However, it is really amazing how warming a candle can be in a snow cave. If the air is still (no matter what is happening outside) a candle can warm your hands and through your hands your whole body in a short time as long as you can stay dry enough to stay warm.
Of all the people stuck on the mountain during that Blizzard we were the only ones at that high an atltitude or higher that didn't lose fingers or toes from frostbite. Although luckily no one died during that storm on the mountain that we knew of I experienced pain in all my joints, legs, arms and hands for several years from almost freezing to death during that 20 hours of almost freezing to death on Mt. Shasta on winter vacation from College in 1970. I tend to overdress whenever it is cold ever since and decided I didn't like camping in the snow anymore much after that near death experience. We were so worn out from the experience and even though we didn't go into shock we all were quite weakened from the experience. So, we spent the next 4 days taking turns thawing ourselves out in a hotel bath. Like I said all my joints hurt from almost freezing to death for several years and my temperature sense never did really come back right so I can't always tell whether I'm too hot or too cold after that. Usually I'm close to almost passing out from the heat or starting to shiver from the cold before I realize that I'm either too hot or too cold from that experience to this day. So, we all had signs of Exposure to the elements that took us about 1 full week to recover from so life started to begin to become normal at all again.
I think the coldest weather I have been in since is in the Himalayas in unheated hotels and unheated Sherpa homes during the winter of 1986 with my family. When we could buy a kerosene stove to heat water for tea and to sterilize water then we also kept warmer at night with the kerosene stove then. But at 10,000 feet the Sherpa homes had a fire pit in the middle of the living room and the smoke went up and out the eves. They didn't use chimneys within traditional Sherpa homes 25 to 50 miles from the nearest road. So heat was only really for cooking. Clothes and body heat was for staying warm even when there was a blizzard outside at it was 10,000 feet in elevation. But the temperatures that I saw usually didn't get below about 10 to 15 degrees Fahrenheit in the Himalayas in any area where people lived so this might be why they didn't heat homes. Maybe when it got colder they all would bring their beds nearby the cooking fire pit and keep the fires going at night. I don't know.
Since 1970 it has been 42 years now since I almost froze to death on Mt. Shasta that one time. However, I have kept up my knowledge about snow caves and ice caves because since one saved my life I have often thought about one saving someone else's life or my own again.
So, if you want to remain dry in a snow cave here are some of the best pointers I have heard about or seen in action. First, make all the walls rounded so if you get the temperature too high the drips go down the walls and don't drop from points down onto you or your sleeping bag. 2nd, elevate your sleeping area from the floor in case melting snow water gathers in pools in some sections of it. 3rd put your snow platform in the center of the snow cave away from the walls so melting snow doesn't get on your bag or you by transferring to your bag or you directly from the walls. And third as I mentioned above your heater will best be a candle or candle lantern to keep your snow cave cozy and warm enough to more easily maintain your body heat until the morning. Also, a snow cave also gets you out of the sun which might prevent snow blindness if you were separated from your sunglasses or snow goggles. I have dealt with someone who went snow blind for a week and it is not fun because I had to take care of them and feed them etc. So, always have really good sunglasses or sun goggles and maybe a back up too so you don't go snow blind in the wilderness. If you lose your sun glasses or goggles the best thing might be to dig a snow cave and close it up except for a vent hole and to light your candle until the sun goes down as long as you have some light for night time travel to your car or wherever, or maybe the moon or stars are out to light your way. I suppose you could take a stick or curved piece of wood or bone or even with a piece of dark or colored plastic and make slits for your eyes like Inuit people did before they had access to sunglasses or sun goggles if you have the right knife or tools but that might take almost a day to make depending upon what raw materials you can find and your skills with a knife or small saw. If it is overcast at all you should be able to travel without sunglasses, goggles or an eye protection of some kind with slits carved or cut into it as long as you can't see the sun at all and not go snow blind in the snow. If you make a slit device be careful you don't fall down because your field of vision is pretty small until you get used to something like that.
So, as you can see it can be important to be prepared for almost anything if you are going to go backpacking or skiing or snowboard or snowshoe camping in the snow.
CO2 'drove end to last ice age'
A new, detailed record of past climate change provides compelling evidence that the last ice age was ended by a rise in temperature driven by an increase in atmospheric carbon dioxide.The finding is based on a very broad range of data, including even the shells of ancient tiny ocean animals.
A paper describing the research appears in this week's edition of Nature.
The team behind the study says its work further strengthens ideas about global warming.
"At the end of the last ice age, CO2 rose from about 180 parts per million (ppm) in the atmosphere to about 260; and today we're at 392," explained lead author Dr Jeremy Shakun.
"So, in the last 100 years we've gone up about 100 ppm - about the same as at the end of the last ice age, which I think puts it into perspective because it's not a small amount. Rising CO2 at the end of the ice age had a huge effect on global climate."
The study covers the period in Earth history from roughly 20,000 to 10,000 years ago.
This was the time when the planet was emerging from its last deep chill, when the great ice sheets known to cover parts of the Northern Hemisphere were in retreat.
The key result from the new study is that it shows the carbon dioxide rise during this major transition ran slightly ahead of increases in global temperature.
This runs contrary to the record obtained solely from the analysis of Antarctic ice cores which had indicated the opposite - that temperature elevation in the southern polar region actually preceded (or at least ran concurrent to) the climb in CO2.
This observation has frequently been used by some people who are sceptical of global warming to challenge its scientific underpinnings; to claim that the warming link between the atmospheric gas and global temperature is grossly overstated.
But Dr Shakun and colleagues argue that the Antarctic temperature record is just that - a record of what was happening only on the White Continent.
By contrast, their new climate history encompasses data from all around the world to provide a much fuller picture of what was happening on a global scale.
This data incorporates additional information contained in ices drilled from Greenland, and in sediments drilled from the ocean floor and from continental lakes.
These provide a range of indicators. Air bubbles trapped in ice, for example, will record the past CO2 concentrations in the atmosphere. Past temperatures can also be inferred from ancient planktonic marine organisms buried in the sediments. That is because the amount of magnesium they would include in their calcite skeletons and shells was dependent on the warmth of the water in which they swam.
"Our global temperature looks a lot like the pattern of rising CO2 at the end of the ice age, but the interesting part in particular is that unlike with these Antarctic ice core records, the temperature lags a bit behind the CO2," said Dr Shakun, who conducted much of the research at Oregon State University but who is now affiliated to Harvard and Columbia universities.
"You put these two points together - the correlation of global temperature and CO2, and the fact that temperature lags behind the CO2 - and it really leaves you thinking that CO2 was the big driver of global warming at the end of the ice age," he told BBC News.
Dr Shakun's team has now constructed a narrative to explain both what was happening on Antarctica and what was happening globally:
- This starts with a subtle change in the Earth's orbit around the Sun known as a Milankovitch "wobble", which increases the amount of light reaching northern latitudes and triggers the collapse of the hemisphere's great ice sheets
- This in turn produces vast amounts of fresh water that enter the North Atlantic to upset ocean circulation
- Heat at the equator that would normally be distributed northwards then backs up, raising temperatures in the Southern Hemisphere
- This initiates further changes to atmospheric and ocean circulation, resulting in the Southern Ocean releasing CO2 from its waters
- The rise in CO2 sets in train a global rise in temperature that pulls the whole Earth out of its glaciated state
He was not involved in the Nature study. Prof Wolff told this week's Science In Action programme on the BBC World Service:
"It looks as though whatever kicked off this whole sequence of events to get out of the ice age was something really, in global terms, rather minor and regional, and yet it led to a sequence of events that led to a complete change in the way the surface of the Earth looked, with ice sheets disappearing.
"So, that just reminds us that although climate might seem quite steady to us because it's been relatively steady for the last few thousand years, it is actually capable of undergoing big changes. And as one famous palaeoclimatologist put it: 'we poke it at our peril'."
Jonathan.Amos-INTERNET@bbc.co.uk and follow me on Twitter