This is a video about "ice spikes" that form in the freezer, and as explained it does so due to the expansion of water when it freezes.
He is talking about ice forming in a standard ice cube tray but those of us who make clear ice cubes in trays know this phenomenon as the "mystery pillar" – one cube (or sometimes two) pops up and starts forming upward out of a tray suspended atop an insulated cooler.
Interestingly in this video the host cites three factors that help ice spikes to form: distilled water, warm freezing temperatures, and a fan blowing on the surface. Well in the case of directional freezing, the water freezes out impurities so that the ice near the surface is basically frozen distilled water; the cooler impacts the rate of freezing; and fans are usually in the way.
In the case of the directional freezing system, rather than spikes forming above the surface, we usually get whole cubes popping up. My theory is that the "ice spike" phenomenon is happening not on the surface of the ice, but through the bottom hole in the tray – pushing the entire cube up from the bottom. Often the new ice forming does up around the sides, so you get something like looks like a cupcake topping on your cube. (Other times it seems the new ice forms below and pushes the whole cube up.)
In any case, I think the "mystery pillar" is the same thing as "ice spikes" as it just makes sense.
