The four types of coastal erosion are solution, hydraulic action, abrasion and attrition. Solution erosion occurs when the ocean’s water is acidic. The acidic water causes some of the rocks along the beach to dissolve into the water. Chalk- and limestone-based coastlines are particularly susceptible to this type of erosion.
The term hydraulic action refers to the phenomenon by which air trapped inside rocks along the coastline becomes compressed from the pressure of the waves. The pressure normalizes when the wave retreats, stressing the rock. When this occurs, the rock surrounding the air pocket weakens, causing it to crumble and collapse. Attrition and abrasion are similar processes that cause mechanical destruction of the coastline. The ocean’s waves pick up sand and rocks. When these rocks smash into other rocks on the coast, it is called attrition; when sand and small pebbles grind a cliff face, it is called abrasion.
Coastal erosion is a natural process; however, tsunamis, storm surges and human activity all cause the rate of erosion to accelerate. According to Texas A&M University, the Atlantic coastline of the United States is eroding at a rate of 2 to 3 feet annually, while the Gulf Coast is eroding as much as 6 feet per year.