Why doesn't an igloo melt inside?
The igloo, a temporary winter hunting shelter to the Alaskan Eskimo
does, in fact, melt inside, but not to a great extent.
The snowflakes falling outside of the igloo, in the harsh Alaskan
winter, quickly melt when they land on its roof, and provide a
replacement layer of insulation for the igloo. The ongoing freezing
and re-freezing of the igloo, hardens it, and transforms the blocks of
snow the Eskimos used in the construction process into a solid, icy,
domed refuge. The igloo can now withstand the weight of a massive
polar bear, should one happen along and have the urge to play "king of
the mountain."
The initial freezing and re-freezing of the igloo takes place at end
of the igloo's construction. First, the men must dig a trench into a
fresh snow- drift, and, using their knives, cut blocks of snow from it
that are specifically shaped to face inward when fully laid out. They
then lay the blocks on their edges to form a circle, cutting them to
size as they go, so that the end result will be a narrowing spiral.
They cap the igloo by dropping a keystone, or block with edges cut
wider above than below, into the remaining gap in the roof, and
"grout" the gaps between blocks of snow with additional snow.
The men then call in the resident expert, the Eskimo woman, to put the
finishing touches on the igloo. Armed with her whale blubber lamp, she
enters the structure, lights her lamp to the highest possible setting,
beats a hasty retreat, and seals the entrance with a block of ice.
Inside the igloo, the snow on the roof begins to melt but, because of
its domed design, the water melts down the sides of the igloo, and
soaks the blocks of snow. When the blocks are almost completely
saturated with water, the Eskimo woman returns, douses her blubber
lamp, and allows the frigid outside air to rush in, transforming the
fragile snow structure into one of hard, solid ice.
The igloo is now prepared for its temporary tenants, whose body heat,
combined with the warmth of one to two blubber lamps, maintain its
exterior temperature rises, does the igloo begin to melt. Hopefully,
the Eskimos will be long gone by then, as the igloo will
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