The Effects of Coastal Erosion on Shoreline Features

Lesson Transcript
Instructor: Rebecca Gillaspy

Dr. Gillaspy has taught health science at University of Phoenix and Ashford University and has a degree from Palmer College of Chiropractic.

Shorelines constantly change due to the pounding of waves that erode coastal structures. Learn about shoreline features that are formed through coastal erosion, such as wave-cut cliffs, wave-cut platforms, sea arches and sea stacks. Updated: 01/15/2020

The Shoreline

If you visited the beach as a kid and then went back with your children 30 years later, chances are the beach and shoreline would look different. This is because coastal areas are constantly changing in form and shape due to the impact of waves.

The pounding of waves is constantly eroding the shoreline, and this creates some interesting shoreline features. In this lesson, you will learn about the effects of coastal erosion, and how the relentless pounding of waves carves out unique features, such as cliffs, platforms, sea arches and sea stacks.

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  • 0:06 The Shoreline
  • 0:43 Coastal Erosion and Headlands
  • 1:29 Wave Refraction
  • 2:11 Wave-Cut Cliffs and Platforms
  • 2:57 Sea Arches and Stacks
  • 3:56 Lesson Summary
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Coastal Erosion and Headlands

Coastal erosion, which is the wearing away of coastal land or beaches, is mainly caused by the impact of waves along the shoreline. This is accentuated during storms when waves are large and crash on shore with a lot of energy.

If a coastal structure, such as a headland, which is a narrow strip of land that projects out into a body of water, contains cracks or crevices, the waves can force water into the openings, dislodging land and rock fragments. Rocky structures along the coast are also subjected to erosion caused by sand and rocks stirred up by and carried within the waves. As the sand and rocks crash into the coast, they grind away land and rock.

Wave Refraction

Waves do not typically strike the shore head on. Wave refraction is the bending of waves as they travel toward the shallow waters of the shore. When waves move from the deep ocean waters to the shallow waters of the shore, the part of the wave closest to the shore hits bottom and slows first.

However, the part of the wave that is still in deep water proceeds at full speed. This contrast in speed causes a bending of the wave crest. As the wave approaches the coast, it is almost parallel to the shore. Because of wave refraction, the energy carried by waves pummels the sides and ends of shoreline protrusions, such as headlands leading to greater erosion.

Wave-Cut Cliffs and Wave-Cut Platforms

Shorelines are carved over time, leaving unique and oftentimes spectacular shoreline features. A wave-cut cliff is a steep rock face created by the eroding action of waves. As waves continue to hit the supporting rocks of the cliffs, a notch is carved into the cliff face. Rocks overhanging the erosion weaken and crumble, causing the cliff to retreat farther inland.

This leaves behind a somewhat flat area found at the base of a wave-cut cliff, called a wave-cut platform. These may be seen during times of low tide when the overlying water recedes. These platforms are sometimes referred to as coastal benches because when they are exposed during periods of low tide, they resemble large benches made of flat rock.

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