Exercised Rocks

In colder climates, the up and down motion of the soil below a poorly built wall can sometimes cause the rocks above to shift out of position, and eventually fall off. This movement is the result of what is called the 'freeze-thaw cycle' Moisture in the earth freezes and pushes upwards, and later when the earth thaws, it causes the ground, and the wall, to subside.



A 'heavy' rock exercises a lot of downward force on the ground, and the actual movement associated with any freeze-thaw cycle may not be that obvious. You'll seldom see individual rocks actually moving, shifting or tipping, but if you're lucky you might see one 'out for a spin'.