As the water rushes up the beach it forms the swash and as it returns down the beach, the backwash . Eventually the material will be deposited on a beach or will form a larger feature such as a spit . Corrasion - this is caused by the waves picking up stones and hurling them at the cliffs. Attrition - any material carried by the waves will become rounder and smaller over time. The nature of a coastline is often determined by its geology .
Some coastlines are very dramatic, with tall, vertical cliffs whilst others are low-lying or marshy.
Some coastlines are straight for miles and miles whilst others are indented with many headlands and bays .Long, fairly straight coastlines result where the rocks are very similar or just one type. If there are many rock-types and they vary in their resistance to erosion, then headlands and bays will form. Many areas have cliffed coastlines. The nature of the cliff again depends on the geology of the rocks. Hard, resistant rocks form tall cliffs with a jagged upper section and a smoothed wave-cut notch at the base.