February 15, 2013 - Kamakura Snow Cave Festival

Children in Yokote, in northern Japan, build little snow caves for this festival. After putting a straw mat on the floor of the snow hut (which looks a lot like an igloo) and lighting a hibachi (a charcoal stove), the snow cave becomes comfortable! The hibachi can be used to heat soup and tea, and families visit each others' snow caves, leaving their boots outside. 

Some kids even sleep in their snow caves!

Isn't it fun to see all the snow huts lit up?

Snow is cold but can keep you warm!

A shelter made of snow or ice can keep you warm. That's because it blocks cold winds, and it insulates you from cold outside temperatures. A candle, hibachi, or other source of heat warms the air inside the snow hut—and the air cannot easily escape to the outside.

Basically, the snow acts in the same way that a blanket or sleeping bag acts—it keeps the warm air in. And the smaller the snow hut, the easier it is to warm up. Your own body may generate enough heat to warm up a tiny snow cave!

Here are instructions for building a snow hut. Notice that one key to this snow hut is to heap up snow loosely. Don't pack the snow. A loosely heaped-up pile of snow traps a lot of insulating air, like the air trapped between the down feathers inside a good sleeping bag.

And here are instructions for building an igloo. Note that this design does use blocks of packed snow! The interior layer of snow melts when it is heated—but then refreezes into ice. And, according to the article, ice is an excellent insulator!

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