Igloo Night in the Storm Zone at Norikura-dake (Elevation 2,640m)
Crossing Norikura-dake on a Unique Route in Fierce Winds
During a spring weather pattern with intense winds, I traversed Norikura-dake via a unique route. My partner’s long-established route design follows a ridge leading directly up to the sharp peak of Eboshi-dake. We spent nearly ten hours breaking trail through beautiful coniferous forests before reaching the volcanic plateau at the summit, where we entered the storm zone. A tent (not that we had one) would have been blown away for sure.
Roof Collapsing in the Wind → Ski Roof Construction
The Norikura Skyline road was covered in blue ice, requiring ice screws for traction. We found a snowdrift with packable snow deep enough for a saw to cut through, and we began constructing our igloo there. The first row of blocks was easy to carve, but beneath that was solid blue ice. We widened the block supply area, transported them, and stacked them.
Around the third row, we attempted to place long blocks as a roof, but the wind knocked them down the moment we looked away. Every time they fell, they snapped in half. After this happened three times, we switched to using skis and poles as beams. That worked like a charm, and the roof was up in no time.
Double Layering the Windward Side to Seal Gaps
Unlike usual, I couldn’t afford to leisurely fill in the gaps. On the windward side, I added an extra exterior wall for a double-thickness defense. Even so, the powder snow carried by the ground blizzard kept infiltrating through the cracks?just like what happened to me on Mt. Fuji before.
My partner was busy collecting blocks at first, but soon, his face was covered in frost formations (sastrugi), and his glasses became useless. The wind-driven snow kept striking his eyes, blinding him from looking upwind. I had him wait under a bivy sack, though even that was a struggle to keep from being blown away.
Bivy sack Sticking to the Wall Thanks to Bernoulli’s Principle
Inside the igloo, snow was still blowing in from the gaps. But when we wrapped ourselves in a bivy sack, something curious happened?it clung to the walls without any support. The fast-moving wind outside created lower pressure compared to the inside, making the tarp stick to the surface. It was a real-life demonstration of Bernoulli’s principle?the same aerodynamic effect that makes an airplane wing generate lift. I’ve been interested in aeronautical engineering since middle school, so I recognized it immediately.
Bernoulli’s effect lasted until morning. But I sure wished the wind would die down sooner…
The Igloo Filled with Snow, but at Least the Wind Was Just Noise
The snow that blew in between the walls and the bivy sack kept creeping inside. Snow piled up on both sides, covered my sleeping bag, and eventually fell underneath me, melted from my body heat, and turned into a freezing puddle. I shivered all night, but it wasn’t life-threatening.
The wind occasionally slammed against the igloo like a powerful punch. I had simulated an emergency plan in case the walls collapsed, but fortunately, they held.
I lit my stove on my lap, drank multiple cups of milk tea, and finished both dinner and breakfast. By morning, the wind was still howling. I stuffed my soaking wet sleeping bag into my backpack, pinched my nose, and made a break for the treeline. The visibility was a blessing. Under clear but violently windy skies, we descended to safety. The trip was only half of what we planned, but given the conditions, that was inevitable. More than anything, I felt deeply satisfied that we managed to push through.
Building an Igloo in Strong Winds with Minimal Snow
I had encountered similar conditions before on Mt. Fuji. There, with little snow, we had to stack flimsy blocks while an endless stream of granular snow particles tumbled through the gaps. That time, my companions swore they were done with igloos for good.
This time, the bivy sack inside made it somewhat bearable, though certainly not comfortable. A larger tarp might have helped if we had stretched it over the exterior, but anchoring it on blue ice would have required screws, and the wind would likely have shredded it anyway.
Of course, the best option would be to avoid camping in such places. But mountains don’t always follow orders. When faced with the unexpected, you just have to make do with what you have.
テーピングテープでシール剥がれを処置。数時間は持つ。赤いシリコンベルトは厚い手袋でも操作できてとても重宝。針金で固定する仕掛けを作ったけど、金属疲労で折れた。横ずれもして外れる。In cold temperatures, ski skins can cause issues. I use taping tape to secure peeling skins?it lasts for a few hours. The red silicone belt is extremely useful as it can be operated even with thick gloves. I once made a mechanism to secure the skins with wire, but the metal fatigued and broke. It also shifted sideways and detached.
When temperatures drop below around -15°C, adhesive skins stop sticking because fine powder snow adheres to the glue surface, preventing them from attaching to the skis. This is especially problematic during ski tours that involve repeated ascents and descents, as the ability to quickly attach and remove skins is crucial. If skins fail to stick, even a small uphill section becomes impassable. I wrap taping tape or a silicone belt around the skins to deal with this issue. A few years ago, I heard a news story about someone who panicked upon facing this problem and called for rescue, unaware of these countermeasures.
Back when I was a student at Hokkaido University (40 years ago), skins were belt-fastened rather than adhesive, so this issue didn’t exist. However, adhesive skins have become the mainstream, and belt-fastened skins are now almost impossible to find.
Even with adhesive skins, it would be ideal if they came with a belt. However, many skins have a poorly designed tail section that lacks a way to secure it once it starts peeling. I wonder how others handle this. Do backcountry skiers remove their skins after one descent and never reattach them? Or do they simply not expect to ski in extreme winter conditions? Maybe they’re unaware of the issue due to fewer extremely cold days caused by global warming.
I modified my skis by cutting the tail and attaching a rubber band to the skin’s tail.
I used to make similar modifications back when belt-fastened skins were common. I cut a notch into the ski tail to prevent the metal hook from shifting sideways, then secured the skins with round rubber to prevent peeling. Nowadays, electric grinders make cutting notches in skis much easier. If elastic cord isn’t strong enough, I’ll try using a bicycle inner tube. Last time, I used wire, but repeated use caused metal fatigue, leading it to snap. Additionally, without a notch, the clip shifted sideways and detached easily.
ノコギリは刃が40ｃｍです。ちょうど刃の後ろ部分の層が「かるかた雪」です。ここだけを使います。The saw blade is 40 cm long. The layer just behind the blade is the ideal “karukata snow.” We only use this part.
湯船から下一段切り出して、もう笹が出てきた。上一段目しかできていないので、切り出し場を求めて「廊下」を作り始めます。After cutting the first layer of blocks from the “bathtub” area, bamboo grass started appearing. With only the first layer completed, I needed another source for blocks, so I began extending a “hallway” to create a new cutting area.
イグルー側から見た廊下の先の「ブロック切り出し場」これまではサイコロ状を切り出し続け、最初の長細いブロックを切って転がしたところ。View from the igloo: The end of the hallway where blocks are cut. So far, I’ve been cutting cube-shaped blocks. Here, the first long block has been cut and rolled.
「切り出し場」からイグルーを「廊下」越しに見たところ。廊下を通って長いブロックを屋根として積む。View from the cutting area: Looking back at the igloo across the hallway. Long blocks are transported through the hallway and stacked as the roof.
手を使ってやさしく手前に転がした。スコップでやってはいけない。両脇がハの字に切れている。これを優しく立てて、ノコで縦切りRolling the block: Using hands to gently roll it forward. Never use a shovel for this step. The sides of the block are cut in a V-shape. Carefully stand it upright and cut it vertically with the saw.
窓はもちろん富士山側にして、最後まで夕景を楽しむ。日が暮れたらサムいから、この隙間を埋めておしまい。Of course, the window faces Mount Fuji, so I can enjoy the sunset until the very end. Once the sun sets, it gets cold, so I’ll fill in this gap and call it a day.
This Time, the Snow Depth Was 60cm
Last week, I had two consecutive igloo expeditions. One of them was in the Higashiyama area of Matsumoto City, on a mountain with an altitude of just under 2000 meters. This region does not have heavy snowfall, and since it is a cold area, the fresh snow never gets a chance to melt. Over time, it also doesn’t get compacted by the weight of more snow from above. The deepest snow I found was about 60 cm. However, that was still enough to build an igloo.
In our usual training sessions, we cut blocks only from the foot area of a 1.5m × 1.5m “bathtub” space and stack them. This method works when there is sufficient snow depth, with a usable snow layer of 30 cm stacked in two or three layers.
This time, the snow depth was 60 cm, but the top 10 cm was a loose powder layer, and the bottom 10 cm had become granular due to ground heat, mixed with bamboo grass and small twigs, making it unsuitable for blocks. That left a 40 cm thick middle layer that was usable for cutting blocks.
External Block-Cutting Method for Igloos in Low-Snow and Cold-Snow Areas
For a one-person 1.5m × 1.5m igloo, if the snow depth is insufficient, the first layer of blocks will be exhausted quickly, and after stacking the second layer, there will be no way to cut more blocks from inside.
To solve this, we extend a hallway outside the “bathtub” area of the igloo, allowing free movement in and out and placing the block supply point nearby. The blocks are cut as we extend the hallway. If the location is on a slope, it’s easier to transport the cut blocks if the supply area is placed uphill. Since the entrance is usually made on the lower slope side, it’s a good idea to create a separate back entrance.
Additionally, when the snow depth is shallow, there isn’t much room to expand below the snow surface. To ensure enough legroom, the igloo should be built slightly larger in advance, around 1.5m × 1.7?1.8m.
As long as the snow layer is good, working outside is much easier since there are no walls or ceilings to restrict movement. Long and sturdy blocks can be cut one after another. A recommended approach is to cut and transport multiple blocks in one go, place them in position, and then assemble the roof all at once at the end. The back “service entrance” can be quickly sealed with just a few large blocks.
Review: How to Cut Large, Long Blocks
Ensure the saw cuts align properly and fully separate the block.
Cut the sides in a V-shape, then tilt the block forward to roll it out.
A shovel is only used to create space for inserting fingers.
Using force with a shovel can break the block. Always roll it by hand.
Stand it up carefully.
Since it is heavy, lower your stance and bring your body close for control.
Cut it vertically with the saw.
Hold both sides with your left hand to prevent it from falling after the cut.
Building igloos requires different techniques depending on the season (December to May) and the snow conditions. There’s always something new to learn?it’s a deep and fascinating process.
個別イグルーを地下でトンネル続きにしています。迷路みたいだよ。The individual igloos are connected underground by tunnels. It’s like a maze!
Igloo workshop＠Nagoya rousan three groups
Impressions from This Session
Igloo-ski demonstrated the process in 36 minutes, and then everyone tried it on their own. I was worried about the low temperature, but the sun came out, and there was no wind, making it another great day for training.
Mizutani-san, in her second attempt, quickly succeeded in sealing the roof this time and was absolutely delighted. Many others followed, successfully completing their igloos one after another.
The snow depth was over 2 meters, and those struggling with block-making kept digging deeper. As a result, many couldn’t reach the ceiling. The trench-cutting method for making blocks wasn’t working well.
Key points for improvement:
Carefully align the saw cuts.
Don’t poke the blocks with a shovel until they start moving at the cut.
When stacking blocks, don’t just place them directly on top?push them inward as much as possible, testing the limits before they fall.
After demonstrating these techniques inside the hole, things progressed much more smoothly.
Many people were using 24 cm saws instead of the recommended 30 cm ones, resulting in blocks that were too small, making it impossible to close the roof. Later, those who had finished lent their saws to others, helping them realize the difference. It became clear that igloos cannot be built properly with short saws.
Failures lead to success. The lessons learned from mistakes are deeply ingrained, and if everyone applies them in their next attempt, I believe they will make significant progress.
Once the igloos were completed, people enjoyed ramen inside their own igloos. The aroma of ramen filled the air at the site.
どうすか？かるかた雪ってのは軽いからこんなに大きくても持ち上がるのです。固くて丈夫だからこんな無茶な積み方でもOKです。What is karukata snow?Because it’s light, you can lift large blocks like this.Because it’s firm and sturdy, you can stack them in seemingly impossible ways.
かるかた雪の長細ブロックなら、わずか数段で、見かけ上、背の低いイグルーができます。With long, narrow blocks of karukata snow, you can quickly build what appears to be a short igloo in just a few layers.
いちばんやりたいこと・イグルーの窓から飽かず絶景を見ることThe Ultimate Goals: Enjoying the stunning view through the igloo window
いちばんやりたいこと：イグルーの中でおいしいもん作って仲間とたべること これはですね、ベトナム屋台料理のエビバナナフライナンプラー浸しです。The Ultimate Goals:Cooking delicious food inside the igloo and sharing it with friends.This time, she made Vietnamese-style shrimp & banana fries soaked in fish sauce.
参加者29人、ひとり風邪で来られず。みな楽しそうで、うれしかったです。We had 29 participants, though one couldn’t attend due to illness. Everyone seemed to have a great time, which made me really happy!
Igloo Workshop @ Gakuto Matsumoto Mountain Forum in February
Thank you always for your inquiries about the igloo workshop! This past weekend, we held the first of two sessions as part of the “Gakuto Matsumoto Mountain Forum,” a mountaineering training series sponsored by Matsumoto City. This time, we conducted the workshop near Jizo-no-Kashira on the Tōmi Ridge in Hakuba Village.
The weather was perfect?clear skies with no wind?and we had a breathtaking view spanning from the Southern Alps to Kubiki and Mt. Naeba. The snow depth was about 2 meters, with the top 50 cm being soft, but underneath, we found the ideal “karukata snow” (light yet firm snow). I believe all participants experienced the joy of working with this type of snow. We were able to cut long blocks just as we wanted!
Key Learnings from This Session
Trench depth matters ? If it’s too shallow (e.g., 20 cm), building becomes difficult. Cut to the full length of the saw (30?40 cm) for better results.
Preventing broken blocks ? Make sure to cut all the way through with the saw before using a shovel to lift them out.
Starting size mistakes ? Some people made their initial igloo area too large, others too small. Giving early guidance could have helped, as both cases were doable but took extra time.
Dealing with soft snow layers ? The top 50 cm of soft snow tends to form potato-shaped blocks, so I had participants discard them liberally.
Stacking technique for second layers and beyond ? Blocks tend to be stacked vertically, but if you take a moment to reposition them slightly closer inward, you can quickly form a roof with a significant difference in structure stability.
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