Houses made of snow delight and fascinate children. The idea of living in an igloo seems so cool. Our intuition tells us that igloos should not work — how could snow be used to build such a warm stable home? This may be a mystery to most people, but it can, in fact, be explained by simple physics!
Building an Igloo
Igloos are built from a collection of snow blocks, which are usually cut from the ground using long blades and knives. A skilled igloo builder stacks these snow blocks in spirals. The builder will shave a slight incline on the top of the blocks, so they look like a ramp. This makes all the snow blocks tilt inward, causing each new layer to spiral up to the top. The builder then adds some vents for air flow and an opening to enter and exit.
There are two key parts to constructing a sturdy igloo. First, the type of snow used has to be dense, dry, and compressed. The snow on the surface is usually too fresh and powdery. The snow way down deep is usually too frozen and may even be ice. The snow in the middle of these layers is just right.
The second key part is the shape of the dome. A stable igloo should be the shape of a parabolic arch; like the Gateway Arch in St. Louis or the Arc de Triomphe in Paris. This type of arch is perfectly shaped to make the snow blocks squeeze themselves together making the igloo very stable. This is really important when building with a weak material like snow. Too much tension and your igloo will collapse. Not enough compression and your igloo will never stay together.
Igloos are also perfect structures for preserving heat. The compressed snow blocks are filled with air pockets making them an excellent thermal insulator. This means they trap heat, like the body heat given off by a person inside the igloo. The temperature inside the igloo can easily be raised by adding more people, or by using oil lamps or candles. Won’t that make the igloo melt? Actually, it won’t. While it is warmer in the igloo than it is outside, the temperature inside an igloo isn’t much above the freezing point. That feels pretty warm when it’s -50° and windy out.
Build Your Own Igloo
You may not be able dig up snow blocks to make a real igloo, but you can still try your hand a building one with a few materials found around your house.
1 bag miniature marshmallows
1 container of frosting or white glue
1 small empty water bottle
1 paper plate
1 frosting bag, plastic knife or baggie