1. OCEAN WAVES
CHANGE
COASTLINES

2. Weathering / Erosion and Waves
Hydraulic pressure: The pounding force of water/waves breaks rock.

3. Corrosion: Minerals such as calcium carbonate and limestone dissolve in the water.

4. Abrasion: rock and sand particles suspended in the water, scrape and gouge surfaces that the water hits.

5. Wave Movement
Headlands: the protrusions of land that extend the farthest out into wave action.

6. Longshore drift: refers to the fact that dominant waves have enough energy to carry silt/sand from headlands along the shore where it is later deposited.
Longshore drift results in some sand being deposited parallel to the shore but connected to the headland. These landforms are known as spits.

8. Longshore drift causes headlands to be eroded and straightened over time.

9. The dominant waves move sediment to form the spit, and secondary waves cause it to hook at the end.

10. Sea Caves / Sea Arches / Sea Stacks
Wave refraction – waves bend as they approach shallow water, the energy of the waves is then concentrated on eroding headlands.

11. Sea Cave Formation waves strike the headland first;
waves refract around the headland and put hydraulic pressure on both sides of the headland;
erosion of the weak portions create caves in the sides of the headland.

12. Sea Arch Formation 
eventually sea caves, on alternate sides of the headland get deeper until they connect forming a tunnel or “arch” through the head land.

13. Sea Stack Formation
continuous erosion, of sea arches, causes the collapse of the ground over the arch;
this leaves a column or “STACK” of land standing alone where the headland was.

15. This process can also straighten out a coastline over time
This process can also straighten out a coastline over time. Notice how deep the bay is before the erosion begins and afterwards.