•They are formed by corrosion in rivers where the fast-flowing water swirls, especially if the river bed is uneven. •Fragments of stones and pebbles carried by the river whirl around, drilling circular depressions into the river bed. •The flowing water keeps the fragments in motion, constantly wearing away the sides of the depressions. •These gradually become deeper and wider to become potholes. •Sometimes, two potholes join to create an even larger pothole.  

Formation of a pothole.

Examples of Potholes in the World