Wave Erosion and Marine
Geology
Take-Away Points
1. Waves are created by the wind
2. Water in a wave oscillates but does not move
with the wave
3. What happens when waves hit the shore
4. Storm surges can be catastrophic
5. How coastlines evolve
6. Deltas are influenced by deposition, tides, and
wave action
7. Reefs are important coastlines in tropical regions
8. Submarine landslides
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
1. Waves are created by the wind
Wave Motions
2. Water in a wave oscillates but does not move with the wave
The Highest Recorded Ocean Wave
2. Water in a wave oscillates but does not move with the wave
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.
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
Rips
• When waves break parallel to a beach, rips
occur
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
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.
5. How Coastlines Evolve
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
5. How Coastlines Evolve
Marine Erosion
•
•
•
•
•
Chemical Attack
Abrasion
Wave Impact
Compressed Air
Backwash
5. How Coastlines Evolve
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
5. How Coastlines Evolve
Longshore Drift
5. How Coastlines Evolve
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
5. How Coastlines Evolve
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
5. How Coastlines Evolve
Secondary Coasts Are Modified by
Marine Erosion or Deposition
5. How Coastlines Evolve
Secondary Coasts
Erosion
• Stack
• Terraces
• 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
5. How Coastlines Evolve
Primary Coastlines Are Very Common
• Drowned
River
Valleys
(Estuaries)
• Drowned
Glacial
Valleys
(Fiords)
5. How Coastlines Evolve
Other Ways Primary Coasts Can
Form
• Deltas
• Volcanic Activity
• Uplift
5. How Coastlines Evolve
Primary and
Secondary
Coastlines
5. How Coastlines Evolve
Delta Coasts
• Deposition-Dominated
• Wave Dominated
• Tide-Dominated
6. Deltas are influenced by deposition, tides, and wave action
The Mississippi – A DepositionDominated Delta
6. Deltas are influenced by deposition, tides, and wave action
Yukon and Nile Deltas – Balance
of Deposition and Wave Action
6. Deltas are influenced by deposition, tides, and wave action
Sao Francisco, Brazil – A WaveDominated Delta
Ganges, Bangladesh – A TideDominated Delta
Reefs Are a Major Type of Coast in
Tropical Areas
7. Reefs are important coastlines in tropical regions
Tarawa – A Typical Atoll
6. Reefs are important coastlines in tropical regions
Reefs Also Form along the Edges
of Large Islands and Continents
These Are Barrier Reefs
• Australia
• Yucatan
• Belize
• West Florida
6. Reefs are important coastlines in tropical regions
Turbidity Flows – Grand Banks, 1929
8. Submarine Landslides
Take-Away Points
1. Waves are created by the wind
2. Water in a wave oscillates but does not move
with the wave
3. What happens when waves hit the shore
4. Storm surges can be catastrophic
5. How coastlines evolve
6. Deltas are influenced by deposition, tides, and
wave action
7. Reefs are important coastlines in tropical regions
8. Submarine landslides