Some causes include inadequate thickness of the pavement section to support the loads traveling across the asphalt, lack of maintenance, and weak or unstable subgrade components. Asphalt deteriorates when “fines” aggregates are worn away by weather and traffic. When the “fines” are worn away, there is nothing to bind the larger aggregates together and the surface begins to ravel. This weakens the pavement section and eventually allows water to penetrate the subgrade, which leads to pavement failure.