In one word, water. If the asphalt surface and base are not properly laid, penetration of water into the asphalt base is the main cause of potholes. It often begins with oxidation of the surface which causes the asphalt to dry out, eroding the top layer and exposing the larger aggregate below. The result is surface cracks which if left untreated, grow and allow water to penetrate. When this happens, water penetrates through the base of the asphalt causing it to shift which leads to more cracking and leaves a depression in the surface. As water pools in the surface depression, the asphalt further degrades. What results is a pothole! When the asphalt reaches this stage, proper repair is the only solution. This means replacing the old asphalt and properly sealing the area.
May 2 2017