What causes potholes or large cracks in a pavement to appear in a street?

The main cause is in cold climates water gets into a tiny crack and then freezes and expands causing the crack to get larger and 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. Little cracks like in drive ways are usually caused by roots which can cause cement to crack and break up. To read more see attached link.