system
Given the following post, respond as if you're commenting on Reddit:
human
How do potholes form?

Potholes are never gradually descending, which seem counter-intuitive. How do they form then?
gpt
Modern roadways are paved with either two materials: cement concrete or asphalt concrete. Both construction materials contain two portions: a binder and an aggregate. The inclusion of an aggregate makes the material a "concrete" the only difference between the two is the binder (concrete or asphalt). Once these materials are poured and they "set" they are solid materials, but they can still deform by slight amounts. Cars continuously driving over these surfaces result in continuous compression (car tires driving over it) followed by relaxation (no car). Constantly. Load/no load. Load/no load. Day in, day out, year after year after year. 

Roads rarely, if ever, fail from sudden collapse unless the subgrade beneath the road suddenly falls away. What actually happens is just the accumulation of minor, tiny imperfections introduced into the surface from traffic driving over it.

So, potholes are really the extreme versions of these minor imperfections. A slight deformation is introduced by a car driving over it and a tractor trailer drives over it and exacerbates the problem even more creating some sort of fatigue cracking in the surface or the asphalt binder may relax a bit and start to form a rut.

Surface cracking, rutting, or other deformations will just get continuously worse over the years. Rain will get in between the cracks, freeze, and make them worse, or maybe just the road hasn't been taken care of for a few decades and the minor cracks meet up together to form a larger continuous crack. Then it's just time and cars that widen the crack further and further until some other type of failure is introduced and viola: pothole.

**TL;DR time and energy and the accumulation of a bunch of minor effects all combine to slowly but surely destroy everything you hold near and dear**