Chapter 2: The Geomorphology of Eroding and Accreting Coasts

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Chapter 2 The Geomorphology of Eroding and
Accreting Coasts
Examples Continental Margins Tectonic
Classification of Coasts Tectonic effects on
coastal sediment supply
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Example Coastlines Morphology
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Terminal Moraine Long Island
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Transgressive Regressive Sequences
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Natural vs Engineered Barrier Island Profiles
Data Westhampton Beach
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Sources of Sand For Littoral Transport
Bluff Erosion Offshore Glacially Deposited Sand
Ridges, Relict Ebb Shoals
Cliff or Bluff Coast
Tide Dominated Riverine
Gravel
2 m
Wave Dominated
Sand
Mixed Energy
Barrier Island
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Spit Accretion Theory
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Spit Accretion Fire Island Inlet
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• Littoral Transport reaches a maximum rate of
  463,015 to 601,657 yd3/yr at Democrat Point (Fire
  Island Inlet)

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Continental Margins
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Continental Shelves broad shallow extension of
the continents (75km wide) Regions of deposition
(rivers, glaciers, scrapped marine deposits,
calcium carbonate) Large bedform features,
reworked by tides, storms, waves
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Continental Slopes continental crust thins into
oceanic crust steep (20km, 1-25 degrees), 5deg
Pacific, 3deg Atlantic extend to depths between
1500-4000 m
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Continental Rise Fan like deposit where the
continental slope intersects the abyssal
plains Formed by turbidity currents
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Tectonic Evolution of Continental Margins
Atlantic Margin passive margin, edge of the
continent is in the middle of a lithospheric
plate, little seismic activity, no
volcanism Pacific Margin active margin, edge of
the continent coincides with a plate boundary,
rim of the Pacific Ocean, ring of fire, seismic
activity and volcanism
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Tectonic Coastline Classification (Inman
Nordstrom)

• Tectonic Setting (Pacific-vs-Atlantic type
  margin)
• Tectonic Setting of opposite side of the
  continent
• Geologic Age of the coast
• Exposure to open ocean conditions
• Collision Coasts
• Continental collision coasts
• Island arc collision coasts
• Trailing Edge Coasts
• Neo-trailing edge coasts
• Afro-trailing edge coasts
• Amero-trailing edgo coasts
• Marginal Sea Coasts

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Continental collision coasts continental
oceanic plate boundary narrow margin, deep
trench seismic activity, coast backed by high
mountains
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Island Arc collision coasts oceanic oceanic
plate boundary narrow margin, deep
trench moderate mountain ranges Ex Japan,
Philippines, Aleutian Islands
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Neo-Trailing Edge Coasts Atlantic type
margins geologically young Ex Red Sea, Gulf of
Aden, Gulf of California
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East African Rift System
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Afro-Trailing Edge Coasts both sides of the
continent are passive margins lack organized
drainage pattern Ex Africa, Greenland
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Amero-Trailing Edge Coasts opposite side of the
continent is an active margin organized drainage
pattern Ex Atlantic coast of NS America and
Europe, India
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Marginal Sea Coasts direct exposure to the ocean
is reduced due to island arc system Ex Gulf of
Mexico, Bearing Sea, Sea of Japan, East and South
China Seas
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Classification Based on Tidal Range
Microtidal lt 2 m Mesotidal 2 4
m Macrotidal gt 2 m
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Classification Based on Wave Energy
Walton and Adams, 1978
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Hydrodynamic Coastline Classification
Tide Dominated Wave Dominated Mixed Energy
(Hayes, 1975)
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Long Island Classification
Amero-Trailing Edge Coast South Shore Significant
Wave Conditions H 1.5 m, T 8
sec Micro-Tidal Environments
Cliff or Bluff Coast
Tide Dominated
Tide Dominated Riverine
Gravel, sand
Gravel
2 m
Wave Dominated
Sand
Mixed Energy
Barrier Island