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Coastal Types
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Introduction Complex Environment
Shaped by tectonics, erosion & deposition, & rocks Several different classification schemes for coasts Erosional or Depositional Depends on whether coast loses or gains sediments Much depends on geological setting Active vs. passive margin Active usually erosional Passive usually depositional These coasts may be modified by Sea level changes Storms Sea Ice Reef-building corals
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Shepard Classification
Coasts modified by processes occurring at land-sea boundary—PRIMARY COASTS Coasts modified by mostly marine processes—SECONDARY COASTS
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Primary Coasts Primary Coasts :
Modified by running water, wind, or land ice Then subsidence or sea level rise Sediments deposited by rivers, glaciers or wind Volcanic activity Uplift and subsidence of land
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Secondary Coasts Formed by: Wave or current erosion
Sediment deposition by waves, currents, tides Alteration by marine plants/animals
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Primary Coasts--Examples
Fjords of Norway, Greenland, New Zealand Land subsided due to ice weight Moraines on coast of Long Island, Connecticut, Cape Cod River Erosion— Chesapeake Bay, Delaware Bay Drowned river valleys Coasts with deltas—e.g. Mississippi, Nile, Ganges Wind modified coasts—Western Sahara, central and northern Oregon Volcanic activity- Hawaii Fault coasts—Tomales Bay, Gulf of California, Red Sea
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Fjords Greenland Fjords Nasa image Norway Nasa image
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Drowned River Mouths Long Island, New York Cape Cod, Mass Nasa Image
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Chesapeake Bay Nasa image Delaware Bay Nasa Image
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Deltas Flow velocity decreases as water flows into lakes or oceans
deposition occurs and may lead to the origin of a delta, which can prograde as sediment is continually supplied by the stream topset, foreset, and bottomset beds
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Sacramento River Delta
NASA
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Ganges River
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Nile River
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Deltas Mississippi Delta, Nasa image Nile Delta Nasa Image
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Mississippi Delta
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Santa Clara River—Small depositional feature
Nasa
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Malibu Creek—smaller, temporary depositional feature
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Wind Modified Coasts Central Oregon Western Sahara, Nasa Image
Flickr.com
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Santa Maria
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Los Angeles Airport
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Volcanic Activity, Kilauea, Hawaii 2005 MSNBC
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Fault Coasts Point Reyes, CA Nasa Image Red Sea Nasa Image
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Secondary Coasts--Examples
Coasts modified by waves—southern California, southern Australia, New Zealand, Cliffs of Dover, England Coasts tend to be straightened Or sea stacks form Coasts formed of rocks with varying hardness Coasts with barrier islands—southeastern United States, Texas Rising sea level flooded coastal dunes Used to be primary coasts Protect coasts from erosion Coasts with sand spits—Washington, Delaware, Mississippii Coasts with reefs—Great Barrier Reef Australia, Pacific Coral atolls
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Straightened Coasts By Waves
Dover Cliff, England Santa Barbara Sylvester, UCSB BBC El Matador Beach, Malibu rockcitynews.com
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Barrier Islands North Carolina gpb.org Galveston, Texas gpb.org
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Sand Spit, Mississippi River, 1954 H. N. Fisk, E. McFarlan, Jr., C. R
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Reefs and Atolls Great Barrier Reef, Australia Nasa image
Atafu Atoll, Tokelau, Southern Pacific Ocean Nasa image
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