ground, of course, expands because water
takes on a lattice
-like structure when it freezes. Hence
, a given mass
of water increases in size when chilled. (Go, try it and see for yourself!) Surprisingly (or not), this represents a powerful
force; freezing water can explode
rocks, collapse hillsides, topple trees, destroy houses, and create an effect on roads something like a natural speed bumb
, as veins of water running underneath the roadway freeze and expand outwards, buckling the concrete
/anything else the road was made out of.
I remember learning about this in my mid-teens, as a girlfriend from a frosty northern place proprietarily explained what all the road signs bearing nothing but the cryptic inscruption "Frost Heaves" meant. In cold enough places, it can become a serious driving hazard...