SHORELINES 20
INTRODUCTION
Shorelines
CHAPTER OUTLINE
1.
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2.
3.
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4.
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5.
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6.
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8.
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9.
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LEARNING OBJECTIVES/FOCUS ON CONCEPTS
20.2 List and discuss
20.4 Describe
20.6 Contrast
20.8 Contrast
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TEACHING STRATEGIES
Muddiest Point:
Permanency of Coastlines.
Tides.
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TEACHER RESOURCES
Web Resources:
USGS
NOAA
NASA Earth Observatory
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EPA
Imagery, Animations, and Videos:
Images
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Animations
Video
ANSWERS TO QUESTIONS IN THE CHAPTER:
CONCEPT CHECKS
20.1 THE SHORELINE: A DYNAMIC INTERFACE
1. An interface is a common boundary where different parts of a system interact. The shoreline is
2. The shoreline is the line that marks the contact between the land and the sea; this line
migrates daily with tides, and over time as sea level rises and falls. The shore is the area that
3. A beach is an accumulation of sediment found along the landward margins of an ocean or
lake. Berms are the relatively flat platforms composed of sand that are adjacent to coast dunes
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20.2 WAVES
1. The three factors that determine the height, length, and period of a wave are (1) the wind
2. As a wave passes, a floating object moves in an imaginary circle: the object moves up and
3. As a wave moves into shallow water the waves speed decreases as it interacts with the
20.3 THE WORK OF WAVES
1. Waves often approach the shore at an angle, therefore their wave base interacts with the
3. Two processes that contribute to longshore transport are the zigzag transport of sediment
20.4 SHORELINE FEATURES
1. Wave-cut cliffs, wave-cut platforms, marine terraces, sea arches, and sea caves are erosional
features of coasts. Wave-cut cliffs form as erosion cuts against the base of coastal land. Wave-
cut platforms are flat, bench-like surfaces left behind by the receding cliffs. Marine terraces are
2. Some barrier islands originated as spits that were severed from the mainland by wave erosion
or by the general rise in sea level after the last episode of glaciation. Others are created when
20.5 STABILIZING THE SHORE
1. Methods of hard stabilization include the construction of jetties, groins, breakwaters, and
seawalls. Jetties are elongate structures, built in pairs, that are intended to prevent deposition
in a harbor or river mouth. Jetties interrupt the longshore movement of sand, and have sand
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20.6 EROSION PROBLEMS ALONG US COASTS
1. When storm waves strike an uninhabited barrier island, the sand that makes up the barrier
2. Natural inflow of sediment to the coast by rivers has been interrupted by the building of many
20.7 HURRICANES: THE ULTIMATE COASTAL HAZARD
1. Hurricane formation is influenced by sea surface temperatures and the Coriolis effect.
Hurricanes are fueled by warm, moist air, and thus form in narrow bands of the oceans where
2. The eye wall of a hurricane is a ring of intense convective activity surrounding the relatively
3. Hurricanes are fueled by the condensation of warm, moist air. When a hurricane travels over
4. The three broad categories of hurricane damage are the storm surge (which is responsible for
the greatest number of hurricane-related deaths), the wind damage, and inland flooding.
5. Winds and storm surge are the most intense on the right side of the eye where winds are
20.8 COASTAL CLASSIFICATION
2. Estuaries are drowned river valleys and are associated with submergent coasts where rising
sea level floods river valleys.
20.9 TIDES
1. The main plane of tidal bulges corresponds roughly to the equatorial plan. Rotation of the
2. Neap tides are smaller tides that occur about the time of the first- and third-quarter moons
when the gravitational forces of the Moon and Sun act on right angles on the Earth, and
3. A flood current is a tidal current that advances into the coastal zone as the tide rises. An ebb
current is a seaward-moving tidal current generated as a tide falls.
EYE ON EARTH
EOE #1 MAUI WAVES
2. As the wave approached the shore, its wavelength decreased.
4. Waves near shorelines have greater elliptical orbits because their bases are slowed by
interaction with the seafloor.
EOE #2 PORT SHELTON, MICHIGAN
1. This feature was constructed to protect a channel (possibly a river) from sediment
deposition.
3. Because this feature extends out into the ocean, it likely interrupts the longshore transport
of sand in the longshore current. When the current reaches the jetty, it slows, depositing
EOE #3 CYCLONE FAVIO
1. The slightly darker colored, circular area roughly between points B and C is the eye. The
eye wall is characterized by the brightest white clouds in the image, nearest the eye.
20.1, these winds speeds correspond to a Category 3 hurricane.
3. The strongest storm surge would be experienced by location B, where the wind speeds are
EOE #4 AERIAL VIEW OF A COAST
2. In the upper portion of the image, at least one marine terrace can be seen as a broad, flat
expanse above current sea level.
3. The eastern coast of the United States is characterized by depositional coasts with broad
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GIVE IT SOME THOUGHT
1. Beyond the surf zone, orbital motion of water would cause your raft to move up and down in a
2. The structures in the image are called groins. They are built to prevent sediment from eroding
along a shoreline. They often appear in long fields, such as this, as downstream locations also
4.
a) No, the city of Houston should not expect to experience Gastons fastest winds and greatest
5. Barrier islands appear stable, but are composed of low ridges of sand that take the brunt of
storm waves. As the waves impact barrier islands, the sand moves in response to the energy
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