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Chapter 12:Agents of Erosion & Deposition
Section 1: Shoreline Erosion & Deposition
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Chapter 12
Section 1 Shoreline Erosion and Deposition
Wave Energy
• When waves crash into rocks over long periods of
time, the rocks are broken down into smaller and
smaller pieces until they become sand.
• Waves usually play a major role in building up and
breaking down the shoreline. A shoreline is the
boundary between land and a body of water.
• As the wind moves across the ocean surface, it
produces ripples called waves. The size of a wave
depends on how hard the wind is blowing and
how long the wind blows.
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Chapter 12
Section 1 Shoreline Erosion and Deposition
Wave Energy, continued
The wind that results from summer hurricanes and
severe winter storms produces large waves that
cause dramatic shoreline erosion.
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Chapter 12
Section 1 Shoreline Erosion and Deposition
Wave Energy, continued
• Wave Trains Waves travel in groups called wave
trains. When wave trains reach shallow water, the
bottom of the wave drags against the sea floor,
slowing the wave down.
• The upper part of the wave moves more rapidly
and grows taller, and begins to curl and break.
These breaking waves are known as surf.
• The time interval between breaking waves is
called the wave period.
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Chapter 12
Section 1 Shoreline Erosion and Deposition
Wave Energy, continued
• The Pounding Surf Tremendous energy is
released when waves break. Crashing waves can
break solid rock and throw broken rocks back
against the shore.
• Breaking waves also wash away fine grains of
sand, which are picked up by the waves and wear
down and polish coastal rock.
• The process continues until rock is broken down in
smaller and smaller pieces that eventually become
sand.
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Chapter 12
Section 1 Shoreline Erosion and Deposition
Wave Erosion
• Shaping a Shoreline Wave erosion produces a
variety of features along a shoreline. Much of the
erosion responsible for coastal landforms takes
place during storms.
• Sea cliffs are formed when waves erode and
undercut rock to produce steep slopes.
• Sea caves are formed when waves cut large holes
into fractured or weak rock along the base of sea
cliffs.
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•Sea arches form when wave
action continues to erode a sea
cave completely cutting through the
rock.
•Sea stacks are offshore columns of
resistant rock that were once
connected to the mainland.
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Chapter 12
Section 1 Shoreline Erosion and Deposition
Wave Deposits
• Beaches are areas of the shoreline made up of
material deposited by waves. Some beach
material is also deposited by rivers.
• Waves carry a variety of materials, including
sand, rock fragments, dead coral, and shells.
• The colors and textures of beaches vary because
the type of material found on a beach depends on
its source.
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Chapter 12
Section 1 Shoreline Erosion and Deposition
Wave Deposits, continued
• Wave Angle and Sand Movement Waves moving
at an angle to the shoreline push water along the
shore and create longshore currents.
• Longshore currents move sand in a zigzag pattern
along the beach.
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Chapter 12
Section 1 Shoreline Erosion and Deposition
Wave Deposits, continued
• Offshore Deposits When waves erode material
from the shoreline, longshore currents can transport
and deposit the material offshore, which creates
landforms in open water.
• A sandbar is an underwater or exposed ridge of
sand, gravel, or shell material.
• A barrier spit is an exposed sandbar connected to
the shoreline.
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