system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why are potholes generally circular in shape and how do they form?
gpt
Potholes can be caused by several things.

If you are in an area where the temperature drops below freezing the cause is most likely water. When water freezes it expands. Small cracks in the road will hold water and the expansion will open the cracks further. The continued abuse on the imperfection by more ice and traffic only makes it worse.

An imperfection in the road bed can also cause settling. This will cause the road surface to sink. Again the constant abuse by traffic only makes it worse.

Heavy trucks will also damage the road. The pressure of the tires will slowly push the road out of the way. You will notice this on roads where there are shallow ditches in the surface where the tires usually run. Also at intersections the force required to suddenly stop can push the road surface forward.

Rain can wash away the road bed. Heat can cause uneven expansion. Physical damage due to impacts with foreign objects create imperfections.

Maintaining roadways is a complex problem.