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A cliff from eroded from two sides produces a up and down
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The top of an arch erodes away, leaving behind a tall

Wave Deposition

Rivers carry sediments from the land to the sea. If wave action is high, a delta will not form. Waves will spread the sediments along the coastline to create beaches (Figure below). Waves also erode sediments from cliffs and shorelines and transport them onto beaches.
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Sand deposits in quiet areas along a shoreline to form a beach.
Beaches can be made of mineral grains, like quartz, rock fragments, and also pieces of shell or coral (Figure below).
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Quartz, rock fragments, and shell make up the sand along a beach.
Waves continually move sand along the shore. Waves also move sand from the beaches on shore to bars of sand offshore as the seasons change. In the summer, waves have lower energy so they bring sand up onto the beach. In the winter, higher energy waves bring the sand back offshore.
Some of the features formed by wave-deposited sand are in Figure below.
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Shores that are relatively flat and gently sloping may be lined with long narrow barrier islands (Figure below). Most barrier islands are a few kilometers wide and tens of kilometers long (Figure below).
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Barrier islands off of Alabama. A lagoon lies on the inland side.
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Barrier islands, such as Padre Island off the coast of Texas, are made entirely of sand.
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Barrier islands are some of the most urbanized areas of our coastlines, such as Miami Beach.
In its natural state, a barrier island acts as the first line of defense against storms such as hurricanes. When barrier islands are urbanized (Figure above), hurricanes damage houses and businesses rather than vegetated sandy areas in which sand can move. A large hurricane brings massive problems to the urbanized area.

Protecting Shorelines

Intact shore areas protect inland areas from storms that come off the ocean (Figure below).
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Dunes and mangroves along Baja California protect the villages that are found inland.
Where the natural landscape is altered or the amount of development make damage from a storm too costly to consider, people use several types of structures to attempt to slow down wave erosion. A few are pictured and described below (Figure below).
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are a long narrow pile of rocks built perpendicular to the shoreline to keep sand at that beach. Groins trap sand on the up-current side so then people down current build groins to trap sand too.
Some structures that protect the shoreline are built entirely in the water (Figure below).
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are visible in this satellite image, built away from the shore and parallel to the shoreline to protect areas from strong incoming waves.
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are built parallel to the beach but onshore. Extremely large storm waves may destroy the sea wall, leaving the area unprotected.
People do not always want to choose safe building practices, and instead choose to build a beach house right on the beach. Protecting development from wave erosion is difficult and expensive (Figure above).

Review Questions

  1. Name three structures that people build to try to prevent wave erosion. How well do they work?

2. What are the names of the parts of a waveform?

3. Describe the process that produces wave refraction.

4. If you were to visit a beach surrounded by coral reefs, what would the beach be made of?


wave-cut platform Level area formed by wave erosion as waves undercut cliffs. wave-cut cliff A sea cliff cut by strong wave energy. spit Long, narrow bar of sand that forms as waves transport sand along shore. sea wall Structure built parallel to the shore on the beach to protect against strong waves. sea stack Isolated tower of rock that forms when a sea arch collapses. refraction A change in the direction of a wave caused by a change in speed. groin Long, narrow piles of stone or timbers built perpendicular to the shore to trap sand. breakwater Structure built in the water parallel to the shore to protect from strong incoming waves. barrier island Long, narrow island composed of sand; nature’s first line of defense against storms. arch An erosional landform that is produced when waves erode through a cliff.