We think of freezing and boiling as opposites, things that happen at very different temperatures. However, under conditions of low air pressure the two can occur together, as we see in this video.
Substances can only be liquid in the presence of a gas to apply vapor pressure. If there is no pressure, or too little pressure, a substance will go straight from solid to gaseous phase as it warms. If you do this in an enclosed space the gas produced will build up, creating pressure as it does so, until a liquid phase is possible. If not enclosed, the gas will escape and the process can continue indefinitely.
