Treebeard's Homepage : Stumpers

Treebeard's Stumper
14 November 2003

Pothole on the Road

All at once it's the winter season, and I have chores to do, like fixing that bad pothole in my road. Even the name "pothole" is a stumper! Sometimes a road just is in bad shape, but sometimes a pothole suddenly appears in a perfectly good road, like a gopher made a wrong turn. I understand how these "axle busters" are formed by frost heaving in colder climates, but why do we get them here in central California? Why are some roads worse than others? Why are potholes usually round, though we always drive across them in the same direction? (I'm sure it's not the gophers!)

Here are a few stages of pothole formation:
Step 1 - Cracks in the road. Note there is already a roundness to the cracks. (This is East Camino Cielo, my road home.)
Step 2 - More cracks, and they now penetrate the asphalt. A few chunks are missing, but the gaps are not round.
Step 3 - A proper round pothole, though it's not yet an "axle buster". It's in the middle of the road, so it gets traffic in both directions.
Step 4 - The pothole that ate the road! (This is Manzanita Lane at Paradise.)

I reckon the real stumper is why these potholes are usually more-or-less round, at least in stage 3. Cars always drive across them (in both directions up here in the mountains!), so why aren't they usually much longer than wide? What other natural processes is this related to?


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