The four ways that waves and tides erode the coast are described below:
1. Hydraulic action; Air becomes trapped in joints and cracks in the cliff face. When a wave breaks, the trapped air is compressed which weakens the cliff and causes erosion.
2. Abrasion; Bits of rock and sand in waves are flung against the cliff face. Over time they grind down cliff surfaces like sandpaper.3. Attrition; Waves smash rocks and pebbles on the shore into each other, and they break and become smaller and smoother.
4. Solution; Weake acids contained in sea water will dissolve some types of rock such as chalk or limestone.