Ice caves are made by meltwater on the inside of a glacier. A hole that is formed gets so big that it becomes a cave. In ice caves the ice is so compacted that it looks blue. Ice caves are dangerous. When the glacier is melting the sides of the cave can get thin and fall in, burying everything. The other danger is that there can be flash floods in the ice cave. If you are too far inside you might not be able to get out fast enough.