Massen et al.* also list the following possible causes: gravitational drainage of air for caves with one entrance, air resonance in large chambers, changes in the volume of air in a cave during flooding, and entrainment of air by water entering the cave.

The latter mechanism is quite common, especially where there is an entrance-filling waterfall, and has the advantage for our wonder of bring a constant flow of air. However this tends to produce only small drafts.