A glacial ice cave can be an explorer's dream. But changing constantly, it can also be a deadly hazard. Glacial ice is created when several seasons of accumulated snowfall compact the underlying layers to a fraction of their former volume. Fire can last through at least one more warm season even if the snow above melts, and eventually the crystals interlock to form bigger and bigger chunks, squeezing out the remaining air bubbles. The glacier now takes on a beautiful blue appearance, because sunlight passing through the ice has had the red end of the spectrum filtered out.
Ice does the job more quickly and at a shallower depth.
The next step in the creation of an ice cave begins when meltwater trickles down through cracks and fissures on the surface, forming small streambeds on the ground below. These small streams grow in size and carve openings as they emerge from beneath the glacier. Through these openings, air begins to circulate when the water is low, and melts more ice on the walls and ceilings of the cave. Slowly, a network of caverns and tunnels is established, complete with a fairyland of ice crystals growing on exposed surfaces which assume strange and unworldly shapes in the eerie blue light. Because glaciers are living and moving things, the caverns do not retain their shapes for long, and a visitor never sees the same cave twice.