The main cause of potholes is that in cold climates water gets into a tiny crack and then freezes and expands, causing the crack to get larger. Then, when cars drive on it, it will eventually cause the top layer of asphalt to break off. In warmer climates the constant wear of vehicles and heat from the sun dries the asphalt and causes the top layers of asphalt to crack, which can widen from rain water. Small cracks in driveways, on the other hand, are usually caused by roots which can cause cement to crack and break up.
The process of pothole formation is generally made up of five steps:
- To start the process of a pothole's formation, moisture must first make its way through openings in the surface of the pavement that begins to "soften up" the underside or base of the road. Here, just below the actual visible surface of the roadway, this moisture gathers and freezes under severe conditions or temperature drops.
- Second, as with anytime water freezes, it expands and or pushes outward, or in this case upward as well. This pressure must go somewhere, and it forces the pavement up, weakening it and the traffic that continues to travel over the weakened pavement further causes stress to the affected area.
- The third step entails waiting patiently for sunshine to make an appearance and dry up the moisture after the damage to the pavement has been done. At this point, a hole is now left behind.
- Fourth, since there is now essentially no underside or base to the pavement, traffic that continues to travel over the weakened spot eventually collapses the spot.
- The fifth and final step to the formation of a pothole is the collapsing of the weakened area. Until road crews can be dispatched to deal with the original hazard created, it will continue to get larger under the stress of traffic continually riding over the edges of the hole and dropping into and out of the pothole itself.
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