1. Coastal Geomorphology:
The Oceans, Coastal
Processes, and Landforms
Chapter 12

2. Ocean Water:
Salinity, Temperature, and Density
• Salinity
– Dissolved mineral salts (sodium chloride, magnesium,
sulfur, calcium, potassium, etc.)
– Differences in salinity are related to evaporation rates
and fresh water inflow
• Avg. max. salinity found in subtropics (high evap., low precip.)
• Avg. min. salinity found in tropical regions (fresh water from high
precipitation, low evaporation due to high atmospheric saturation)

3. Ocean Water
• Temperature
–Decreasing temperatures with increasing latitude
•Polar water = cold, equatorial water = warm
–Decreasing temperatures with increasing depth
•Deeper waters are colder (sunlight can’t reach, there
is little or no mixing)
–Western sides of oceans are warmer due to ocean
circulation patterns (see next slide)

4. Warm and Cold Ocean Currents

5. Ocean Water
• Density
– Related to temperature
• low temp. = high density
– Molecules are less active, so cold water contracts
– Related to salinity
• high salinity = high density
– More solids in the water (salts) increases overall density
– Related to depth
• deep water = high density
– Pressure of water above compresses deep water, increasing density

6. The Movements of The Oceans
• Tides
• Currents
• Wave motion

7. Tides
• A “bulge” in the
world’s oceans, caused
by the gravitational
pull of the moon and
sun
Fg = G m1 m2
d2

8. Tides
• Tidal range—the difference
between high and low tide
• Affected by the shape of
the coastline and seafloor
• Spring tides—highest tides,
strong and quick
– Occur when sun, moon, and
Earth line up (the sea
“springs” up and back)
• Neap tides—lowest tides
– Sun and moon at right angles
with respect to Earth
– Neap = A low incline of bend
(when graphed)

9. Monthly Tidal Cycle

10. Extreme High Tides
• The Bay of Fundy
• A 50’ (15m) tidal
fluctuation is common (x2)
•A tidal bore (several in. to
several ft. high) rushes miles
up the Petitcodiac River in
New Bruswick

11. Landforms shaped by extreme tides

12. Extreme tides: Mont Saint Michel, France
Low tide High tide
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13. Currents: Surface

14. Currents: Thermohaline Circulation

15. Waves and Wave Dynamics

16. Waves and Wave Dynamics
• Period—The time it takes two successive
waves (from crest to crest, or from trough to
trough) to pass a given point
• Fetch—The distance over which the wind
blows, creating waves

17. Waves and Wave Dynamics
• Factors affecting open ocean waves:
–Fetch
•The greater the distance over which the wind blows,
the larger the waves
–Wind strength
•The stronger the wind, the larger the waves
–Wind duration
•The longer the wind blows, the more waves will be
created

18. Waves and Wave Dynamics
Wave base

19. Waves of Oscillation (Transition) and
Waves of Translation
• Water molecules on the open ocean move in a
circular motion
– The motion passes through the water, but the water
doesn’t move forward (to oscillate is to move up and
down)
– What moves the water forward is wind blowing over the
surface and the movement of currents
• Water molecules that reach the shore have their
circular motion interrupted
– Their energy is translated into the shore face (it passes
from the water to the land, where it does work to move
material—like sand—around)

20. Waves and Wave Dynamics
Waves of translation
Waves of oscillation

21. Wave Break

22. Wave Refraction and
Longshore Current
• As waves reach the shore and “feel” the bottom,
they slow and break
• The direction of wave break follows the underwater
topography
• This causes the wave to “bend” and become more
parallel to the shoreline
– This bending is called wave refraction
• As it breaks from one side to the other, it creates a
current
– This current, called the longshore current picks up
and moves sediment (sand) down the shore

23. Wave Refraction,
Longshore Current and Beach Drift

24. Erosional Environments
• If there is not enough sediment replacing what’s
being lost through wave erosion/longshore current,
erosion will occur, creating a rocky coastline
– Dammed or channelized streams
• sediment can’t get to the beach
• Erosive environments create distinctive landforms
– rocky headlands and pocket beaches, sea arches and
sea stacks, wave-cut cliffs, wave-cut platforms, wave-
built terraces, etc.

25. Wave Energy is Concentrated at
Headlands and Dissipated in Bays

26. Wave Motion and Wave
Refraction

27. Wave Motion and Wave
Refraction

28. Laguna Beach, CA
Headlands

29. Headland Erosion
and the Formation of Sea Arches

30. Stacks and Cliffs
Victoria, Australia

31. The Holderness Coast is one of Europe's fastest eroding coastlines. The
average annual rate of erosion is around 2 metres per year. The main reason
for this is because the bedrock is made up of till. This material was deposited
by glaciers over 18,000 years ago.

32. Depositional Environments:
The Structure of a Beach

33. Common Depositional Landforms

34. Barrier Island Structure

35. Barrier Island Coast
Padre Island, Texas
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36. Lagoons, Marshlands, and the
Formation of New Coastlines

37. Coastal Stabilization and
Human Impact
“Any serious researcher would be hard-
pressed to find a marina, a sea wall, or any
other human structure along the shoreline
that does not pose some long-term
deleterious effects to both the natural and
cultural environments it attempts to protect.”
--Physical Geography: Earth’s Interconnected Systems
Angela Orr, 2007

38. Coastal Stabilization and Human
Impact
• Damming and channelizing streams
–Causes a loss of sediment where streams empty
into the sea. Without sediment, the beach will
erode away.
• Groynes (groins)
• Seawalls
• Breakwaters and jetties
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39. Coastal Stabilization Structures

40. Groynes (groins)
40

41. • Can you tell which way the longshore current is
moving material?
• Once you put up one groyne, you need to keep
building them all along the shore to keep erosion from
destroying property downshore from your first
structure. Note the severe erosion at the top of the
photo where the groynes stop.
41

42. Breakwater

43. Breakwater
• These breakwaters are creating tombolos in
the wave shadow behind them.
43

44. The Example of Marina del Rey, CA