Download Garrison Oceanography 7e Chapter 12

Oceanography
An Invitation to Marine Science, 7th
Tom Garrison
Chapter 12
Coasts
Coasts Are Shaped by Marine
and Terrestrial Processes
Coastal regions are important because they interconnect sea with
land.
They are affected by both marine and terrestrial processes.
Coasts are indicators of eustatic changes, variations in sea level.
Glaciation, global warming, volcanic outgassing, tectonic activity, and
weather events all have their affects.
Coasts Are Shaped by Marine
and Terrestrial Processes
Coasts can either be:
Erosional- caused primarily by
loss of materials.
Water, wind, weather, and plants
can cause erosion.
Depositional- caused by the
addition of materials.
Accumulation through volcanoes,
waves, tides, and rivers can
cause deposition.
Shorelines Can Be Straightened
by Selective Erosion
The rate of erosion is dependant on 2 factors:
The energy or force of erosion and the hardness of the rock
Marine erosion is usually most rapid on high-energy coasts, areas
frequently battered by large waves.
Low-energy coasts are only infrequently attacked by large waves.
Concept Check 12.1-12.2
1. Name 2 types of marine forces that shape the coasts.
2. Name 2 types of terrestrial forces that shape the coasts.
3. Name the process responsible for raising and lowering
sea level.
4. Using fig. 12.2 when did the oceans hit a low point,
explain why.
5. Explain the difference between erosional coasts and
depositional coasts.
6. Give 2 factors that dictate the rate of erosion.
7. Name 2 types of coastal features formed by erosion.
Beaches Often Have a Distinct
Profile
A beach is a zone of loose particles that covers a
shore.
What are the features of a beach?
• Berm
• Berm crest
• Backshore
• Foreshore
• Beach scarp
• Longshore trough
• Longshore bars
Draw a labeled diagram of a
beach in your journal
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Include the following along with definitions:
Berm
Berm crest
Backshore
Foreshore
Beach scarp
Longshore trough
Longshore bars
Waves Transport Sediment on
Beaches
A longshore current moves
sediment along the shoreline
between the surf zone and the
upper limit of wave action.
Beach textures depend on
particle size, wave action, and
slope. The flatter the beach,
the finer the material.
Sand Input and Outflow Are
Balanced in Coastal Cells
Longshore drift- movement of
sand along the coast by wave
action.
Longshore current- movement of
sand along the coast by currents.
Coastal sediment transport cells.
Sections of coast in which sand input and
sand output are balanced are referred to
as coastal cells.
Coastal configurations…
Barrier islands-rises that form and run
parallel to the coast
• Formed possibly 6000 ears ago by higher
sea levels
• Susceptible to forces of nature
• Provide protection to the mainland (i.e.
Miami Beach, West Palm Beach, Atlantic
City)
Our barrier Island
Coastal configurations cont.
• Sea islands – like barrier islands, except
they were once part of the mainland
• Deltas – form as sediment deposit at the
mouth of a river
Coastal configurations cont…
• Reefs – structures made by the deposition
of skeletons of coral animals
• Water must be clear, well lit, and warm
• There are 3 types:
– Fringing
– Barier
– atolls
Coastal configurations…
• Mangroves – dominated
by shallow water where
trees can grow in
saltwater
• Estuaries – sheltered
areas which contain a
mixture of saltwater and
freshwater
– The “nurseries” of
marine life
– Majority of marine life
starts here
Human dependence
• Coastal areas are subject to nature and
man.
• Nature – weather, tides, waves
• Man – overdevelopment, pollution,
overuse
• Highly prized for tourism, real estate
• Should be valued for importance to nature
• Constant dredging of sand is expensive
The Characteristics of U.S. Coasts
• The Pacific Coast - An actively rising margin
where indications of recent tectonic activity
can be observed.
• The Atlantic Coast - A passive margin on
the trailing position of the North American
plate.
• The Gulf Coast - Smaller wave size and a
smaller tidal range characterize the Gulf
Coast.
Humans Have Interfered in
Coastal Processes
A map showing shore erosion by region. One example of shore
erosion is the lighthouse on Cape Hatteras, which was moved
during 1998 and 1999 to protect it from destruction. It was
threatened by rising sea levels and a changing shoreline.