Wave Erosion and Marine
Geology
How waves behave
How the sea modifies coastlines
Waves
Essential Points
1. Waves are created by the wind
2. Water in waves oscillates but does not
move with the wave
3. What happens when waves hit the shore
4. Storm surges can be catastrophic
How Waves Behave
Wave Fetch
Wave Fetch
The Highest Recorded Ocean Wave
1. Waves are created by the wind
Global Wave Heights
1. Waves are created by the wind
Freak Waves
• Addition of waves
of different
frequencies
• Theoretically
could reach 200
feet in Gulf of
Alaska
• One nearly sank
the Queen Mary in
WWII, with 15,000
troops aboard.
1. Waves are created by the wind
Wave Motions
• Particles in a wave travel circular paths
• The water in a deep-water wave does not
move forward
• Below wave base, wave effects are negligible
2. Water in a wave oscillates but does not move with the wave
Wave Motions
2. Water in a wave oscillates but does not move with the wave
When Waves Meet the Shore
When the bottom interferes with wave motion, the
wave steepens and the top overtakes the bottom.
3. What happens when waves hit the shore
Wave Refraction
• Waves change path when they reach shallow
water
• Wave energy is concentrated on headlands and
spread out in bays
3. What happens when waves hit the shore
Wave Refraction off Cape Cod
3. What happens when waves hit the shore
Rips
• When waves break parallel to a beach, rips
occur
3. What happens when waves hit the shore
Rips, Lake Superior
Oblique Rips
3. What happens when waves hit the shore
Storm Waves: Galveston, Texas, September 8, 1900:
• 6000-8000 dead
• 3600 houses destroyed
4. Storm surges can be catastrophic
Raising Galveston – 6 in. to 17 ft.
“A rickety maze such as Dr. Seuss might have drawn”
The Lift in Progress
Pumping in
the Sand
4. Storm surges can be
catastrophic
The Galveston Seawall
4. Storm surges can be catastrophic
Essential Points
1. Waves are created by the wind
2. Water in waves oscillates but does not
move with the wave
3. What happens when waves hit the shore
4. Storm surges can be catastrophic
How Waves Behave
How the sea modifies coastlines
Essential Points
1. Wave Action erodes or deposits material
along coastlines
2. Types of coastline
3. Deltas are governed by deposition, waves,
and tides
4. Reefs are a special type of coastline in
tropical regions
5. Global sea level is affected by ice ages and
plate tectonics
How the sea modifies coastlines
In the long run, nothing is as
futile as trying to resist shoreline
change.
Change can be resisted for a while,
but when the water wants
something badly enough, it will
come in and take it.
1. Wave Action erodes or deposits material along coastlines
Property
Values and
Shoreline
Erosion
• If more than half the original lot is left, it’s
Location, Location, Location
• After that, it becomes obvious there soon
won’t be any location left
1. Wave Action erodes or deposits material along coastlines
Marine Erosion
•
•
•
•
•
Chemical Attack
Abrasion
Wave Impact
Compressed Air
Backwash
1. Wave Action erodes or deposits material along coastlines
Water Velocity and Erosion
1. Wave Action erodes or deposits material along coastlines
Longshore
and Beach
Drift
• Most Beach Sand Is Created by Weathering and
Carried to Coasts by Rivers
• Beach Sand Moves along the Coast by Longshore
and Beach Drift
1. Wave Action erodes or deposits material along coastlines
Beach Drift, New Jersey
Types of Coast
Degree of Modification
• Primary - Not Modified Much by Wave Action
• Secondary - Highly Modified by Wave Action
History
• Emergent - Land Rises or Water Level Falls
• Submergent - Land Sinks or Water Level Rises
Dominant Process
• Erosional
• Depositional
2. Types of coastline
Effects of the Pleistocene
• Sea level has risen at least 100 meters in
the last 18,000 years
• Most coastlines globally are submergent
• Primary coastlines are very common
2. Types of coastline
Secondary Coasts Are Modified
by Marine Erosion or Deposition
Secondary Coasts
Erosion
• Stack
• Terraces
• Tombolo
• Erosion rate becomes very
slow
– wave energy dissipated
crossing the wave-cut
terrace.
– Cliffs become higher,
meaning more material to
move.
Deposition
• Spit
• Lagoon
• Baymouth Bar
• Barrier Bar
2. Types of coastline
Primary Coastlines Are Very Common
• Drowned
River
Valleys
(Estuaries)
• Drowned
Glacial
Valleys
(Fiords)
2. Types of coastline
Estuaries, Chesapeake Bay
Tidal
Marshes,
Chesapeake
Bay
2. Types of coastline
Fiord Coast, Labrador
Other Ways Primary Coasts Can
Form
• Deltas
• Volcanic Activity
• Uplift
2. Types of coastline
Primary and
Secondary
Coastlines
2. Types of coastline
Baymouth Bar, Michigan
Wave-Cut Platform, California
Footer
Coastal Terraces, California
Sea Stacks, Washington
Former Stack, Michigan
Sea Caves, Apostle Islands
Wave-Cut Arch, Lake Superior
Delta Coasts
• Deposition-Dominated
• Wave Dominated
• Tide-Dominated
3. Deltas are governed by deposition, waves, and tides
The Mississippi – A DepositionDominated Delta
3. Deltas are governed by deposition, waves, and tides
Yukon and Nile Deltas – Balance
of Deposition and Wave Action
3. Deltas are governed by deposition, waves, and tides
Sao Francisco, Brazil – A WaveDominated Delta
Ganges, Bangladesh – A TideDominated Delta
Reefs Are a Major Type of Coast
in Tropical Areas
4. Reefs are a special type of coastline in tropical regions
Fringing Reef, Tahiti
Tarawa – A Typical Atoll
4. Reefs are a special type of coastline in tropical regions
Reefs Also Form along the Edges
of Large Islands and Continents
These Are Barrier Reefs
• Australia
• Yucatan
• Belize
• West Florida and the Keys
4. Reefs are a special type of coastline in tropical regions
Sea Level and Tectonic Activity
5. Global sea level is affected by ice ages and plate tectonics
Depth of Ocean Crust
5. Global sea level is affected by ice ages and plate tectonics
Sea-Floor Spreading and Sea Level
5. Global sea level is affected by ice ages and plate tectonics
Sea Level and Tectonic Activity
5. Global sea level is affected by ice ages and plate tectonics
Essential Points
1. Wave Action erodes or deposits material
along coastlines
2. Types of coastline
3. Deltas are governed by deposition, waves,
and tides
4. Reefs are a special type of coastline in
tropical regions
5. Global sea level is affected by ice ages and
plate tectonics
How the sea modifies coastlines