Made by: Natural melting
Most glacier caves are started by water running through or under the glacier. This water often originates on the glacier’s surface through melting, entering the ice at a moulin and exiting at the glacier’s snout at base level. Heat transfer from the water can cause sufficient melting to create an air-filled cavity, sometimes aided by solifluction. Air movement can then assist enlargement through melting in summer and sublimation in winter.
Some glacier caves are formed by geothermal heat from volcanic vents or hotsprings beneath the ice.
Some glacier caves are relatively unstable due to melting and glacial motion, and are subject to localized or complete collapse, as well as elimination by glacial retreat.
This is particularly interesting to me because the transformation between water, ice and vapour results in this kind of beautiful scene. And we can think more about the effect of different forms of one material.