coastal types. introduction complex environment – shaped by tectonics, erosion & deposition,...
Post on 20-Dec-2015
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Coastal Types
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
Shepard Classification
• Coasts modified by processes occurring at land-sea boundary—PRIMARY COASTS
• Coasts modified by mostly marine processes—SECONDARY COASTS
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
Secondary Coasts
• Formed by:– Wave or current erosion– Sediment deposition by waves, currents, tides– Alteration by marine plants/animals
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
FjordsGreenland FjordsNasa image
NorwayNasa image
Drowned River MouthsLong Island, New YorkNasa Image
Cape Cod, MassNasa Image
Chesapeake BayNasa image
Delaware BayNasa Image
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, andbottomset beds
Sacramento River Delta
NASA
Ganges River
Nile River
DeltasMississippi Delta,Nasa image
Nile DeltaNasa Image
Mississippi Delta
Santa Clara River—Small depositional feature
Nasa
Malibu Creek—smaller, temporary depositional feature
www.santamonicabay.org/.../ tabid/77/Default.aspx
Wind Modified CoastsWestern Sahara,Nasa Image
Central OregonFlickr.com
Santa Maria
Los Angeles Airport
Volcanic Activity, Kilauea, Hawaii 2005MSNBC
Fault CoastsPoint Reyes, CANasa Image
Red SeaNasa Image
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
Straightened Coasts By Waves
BBC
Dover Cliff, England
Santa Barbara
Sylvester, UCSB
El Matador Beach, Maliburockcitynews.com
Barrier Islands
North Carolinagpb.org
Galveston, Texasgpb.org
Sand Spit, Mississippi River, 1954H. N. Fisk, E. McFarlan, Jr., C. R
Reefs and AtollsGreat Barrier Reef, AustraliaNasa image
Atafu Atoll, Tokelau, Southern Pacific OceanNasa image