Driving through rural New Hampshire I noticed a temporary road sign. The triangular yellow sign had “FROST HEAVES” written on it. Being that I am not exactly native to New England, I had no idea what it was. Since I was driving, I asked my Apple CarPlay-connected friend, Siri, what a frost heave was. She cited Wikipedia:

Frost heaving (or a frost heave) is an upwards swelling of soil during freezing conditions caused by an increasing presence of ice as it grows towards the surface, upwards from the depth in the soil where freezing temperatures have penetrated into the soil (the freezing front or freezing boundary). Ice growth requires a water supply that delivers water to the freezing front via capillary action in certain soils. The weight of overlying soil restrains vertical growth of the ice and can promote the formation of lens-shaped areas of ice within the soil. Yet the force of one or more growing ice lenses is sufficient to lift a layer of soil, as much as 1 foot (0.30 metres) or more. The soil through which water passes to feed the formation of ice lenses must be sufficiently porous to allow capillary action, yet not so porous as to break capillary continuity. Such soil is referred to as “frost susceptible”. The growth of ice lenses continually consumes the rising water at the freezing front.

Since I’m not very bright, I still had no idea what a frost heave was. I shrugged it off and continued driving on the crappy secondary road. And then, our friends at Auto Off Topic Podcast posted this video. Suddenly, it all made sense. Frost heaves, be aware of them!