Observations and results
Did the shoreline erode, or recede from the water, after you bobbed the water bottle up and down for two minutes? Did most of the shoreline erode less when there was a headland, especially the shoreline closest to it?
As waves hit the shoreline over time they erode it and push it further inland. When larger and stronger waves hit the shoreline, such as in a storm, more shoreline is eroded. On a beach that is made up of a mixture of small sand grains and larger, dense rocks, the sand will be eroded away first, leaving behind the larger rocks. Over time this can create a headland—an outcropping of the larger rocks—and a bay nearby. The headland receives most of the waves' energy and consequently protects the bay from erosion. Artificial headlands are sometimes created for this purpose: to prevent coastal erosion. In your model, you should have seen that less shoreline eroded near the headland, but further away from the headland, along the sides of the pan, more erosion occurred and the shoreline was pushed farther inland because the more distant shoreline was not as well protected by the headland.
More to explore
What Causes Beach Erosion? from Scientific American
Shoreline erosion and migration from the State of Delaware
A guide to managing coastal erosion in beach/dune systems: Artificial headlands from the Scottish Natural Heritage
Restore Your Shore from the Minnesota Department of Natural Resources
Building Beaches from Science Buddies
This activity brought to you in partnership with Science Buddies