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Coastal Processes

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Title: Coastal Processes


1
20 Coastal Processes and Terrain
2
The Impact of Waves and Currents on the Landscape
  • Coastal Processes
  • Erosion Waves, mainly
  • Deposition Currents, mainly
  • Rocky cliffs and headlands
  • Main erosional features
  • Beaches and sandbars
  • Main depositional features

3
Coastal Processes
  • Erosion and Deposition
  • Involve the transfer of energy from the
    atmosphere to the hydrosphere (ocean) and then to
    the lithosphere (land).

4
  • Geomorphic agents
  • Waves
  • Wind-generated waves
  • Fetch
  • Other agents
  • Longshore (littoral) currents
  • Tides and tidal currents
  • Volcanic eruptions and earthquakes
  • Tidal (storm) surges
  • Long-term (tectonic and climatic) effects on sea
    level change
  • Reef-building corals
  • Sea ice and glacial ice

5
Waves
  • Wave Motion and Wave Refraction
  • Tsunami
  • Animation
  • Definition A disturbance in water caused by
    energy passing through it.
  • Wave terms wavelength, wave crest and trough,
    swash
  • Swell, height, and period
  • Fig. 20-2

6
  • Waves of Oscillation and Translation
  • Wave of Oscillation energy and mass move
    differently
  • Fig. 20-2

7
  • Wave of Translation energy and mass move in the
    same direction (horizontally)
  • Fig. 20-3

8
  • Wave Refraction water changes direction because
    of ocean bottom and/or land mass
  • Fig. 20-5

9
  • Headland erosion (idealized)

Wave Refraction (blue lines)
Headland
10
  • Fig. 20-6. Headland erosion in Australia along
    the southern coast of the state of Victoria.

11
  • Wave Erosion
  • Hydraulic pounding
  • Chemical action
  • Sea cliff erosion
  • Fig. 20-7

12
  • Tsunami (Seismic Sea Waves)
  • Rapid, pronounced vertical displacement
  • Main causes
  • Earthquake (submarine)
  • Landslide (submarine)
  • Volcanic island eruption

13
  • Fig. 20-8. Formation of a Tsunami.

Ex. 2004 Sub-oceanic 9.0 Earthquake and
Resulting Indian Ocean Tsunami
14
  • Tides
  • Animation (Tides)
  • Significant erosion agents in narrow bays,
    margins of shallow seas, and straits.
  • Fig. 20-9. Bay of Fundy has the highest tidal
    range in the world. Tidal action created these
    pedestal rocks on the edge of the bay.

15
  • Changes in Sea Level and Lake Level
  • Causes
  • Tectonic uplift or sinking of landmass
  • Eustatic sea-level change increase or decrease
    in the volume of water in the oceans (ice age vs.
    interglacial)
  • Fig. 20-10. Northern California coast is
    experiencing tectonic uplift.

16
  • Global Warming and Sea-Level Change
  • Causes
  • Glacial melting - more water
  • Thermal expansion - water takes up more space
  • Consequences by 2100
  • Vertical Sea Level Rise Up to 0.5 m (20) rise
    globally
  • Horizontal Retreat of Shorelines Up to 30 m
    (ca. 100 ft.) in some coastal areas
  • Ice Push
  • Annual freezing of sea ice causes near-shore ice
    to push against the land, causing minor erosion
  • Arctic and Antarctic regions only

17
  • Organic Substances
  • Aquatic organisms and calcium carbonate
    secretions
  • Reef-building coral polyps
  • Stream Outflow
  • Source of sediment for beaches
  • Fig 20-11. Sediment plume of the Betsiboka River,
    Madagascar.

18
  • Currents and Coastal Sediment Transport
  • Longshore Currents
  • Wave refraction

19
  • Beach Drifting
  • Particle-by-particle transport of beach material

20
  • Fig. 20-13. Waves approaching the shore obliquely
    causes longshore currents and beach drifting.

21
  • Coastal Deposition
  • Sediment budget of a shore
  • Input from longshore current and wave action
  • Output from storm wave action, mainly.
  • Large beaches and sand dunes
  • Inputs exceed outputs.
  • Sediment budget

Fig. 20-14
  • Fig. 20-14. One of the largest coastal dune
    complexes is on the Oregon coast.

22
Coastal Landforms
  • Depositional Landforms
  • Animation (Coastal Stabilization
    Structures)
  • Beaches
  • Most widespread marine dispositional feature on
    land
  • Mostly sand deposits
  • Extent
  • Inland margin (storm wave deposits)
  • Seaward margin (neap tide line)

23
  • Components of the beach environment
  • Fig. 20-15

24
  • Spit and related features
  • Spit - linear strand of marine sediments attached
    to shore
  • Formation usually involves longshore current
    transport
  • Related features
  • Lagoon
  • Estuary
  • Delta
  • Fig. 20-16. Types of spits and the longshore
    current.

25
  • Idealized drawings of formation of spit and
    related features

Bay
Land
Ocean
26
  • Tombolo formation

Land
Ocean
Small island, sea stack
27
  • Photographs of spits and related features
  • Fig. 20-17. Spit at Cape Henlopen, Delaware

28
  • Fig. 20-18. Tombolo and Mont Saint Michel on the
    northwest coast of France.

29
  • Barrier Islands
  • Coastal islands
  • Parallel to the shoreline
  • Sand and other materials
  • Complex origins
  • Pleistocene sediments washed toward mainland
  • Longshore transport and spit segmentation

Barrier Island
30
  • Lagoon formation
  • Landward side of barrier island, protected from
    large waves
  • Low energy environment, fine mud deposits (tidal
    flats)
  • Fig. 20-19

31
  • Human Alteration of Coastal Sediment Budgets
  • Beach starvation (unintentionally shrinking
    beaches)
  • Dam construction on rivers reduces sediment
    discharge into oceans, starving nearby beaches of
    sand
  • Old debris dam in Santa Ynez Mountains, near
    Santa Barbara, CA (Richard A. Crooker photo)

32
  • Beach nourishment (re-building beaches)
  • Adding sand to beaches by dredging and pumping
    sand from off-shore
  • A slurry of sand and water is pumped on shore and
    the sand is spread onto the beach of Rehoboth
    Beach, DE (Richard A. Crooker photos) (overlay,
    dissolve)

33
  • Beach preservation (maintaining beaches)
  • Build structures that modify longshore transport
    and wave action in order to keep sand on beaches
  • Jetty, groin, breakwater
  • Fig. 20-22

34
  • Shorelines of Submergence
  • Ria Shorelines
  • Hilly or mountainous areas
  • flooded valleys become estuaries
  • - Fig. 20-23. Chesapeake Bay.

35
  • Fjorded Coasts
  • Fjord glacial trough that is inundated by the
    sea
  • Fig. 20-24

36
  • Shorelines of Emergence and Erosion
  • Wave-cut Cliffs and Platforms
  • Marine Terraces
  • - Fig. 20-27. Near Fort Ross, CA

37
  • Coral Coasts
  • Coral Polyps
  • Reef-building varieties, warm tropical waters
  • Fig. 20-28

38
  • Shallow-water Platforms
  • Australias Great Barrier Reef

A Major Problem Coral Bleaching death of the
entire ecosystem Why?
  • Fig. 20-30

39
  • Sinking Islands
  • Three types of reefs

40
  • Fig. 20-31

41
  • Fig. 20-32. Part of the fringing reef on the
    island of Moorea, French Polynesia.

42
Homework
  • Read Ch. 20
  • Create a study guide including material from Ch.
    20.
  • Summary, list, notes, review slides

43
Coastal Processes and Terrain Ventura County
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Activity
  • Read Ch. 20
  • BEACH FIELDTRIP! (tba)
  • Review next time
  • Start preparing for the final, covering all
    lectures, activities, and homework throughout
    chapters 11 to 20.
  • Suggestion Write a study guide and resolve
    unknowns... Im here to help!
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