Coastal Types. Introduction Complex Environment – Shaped by tectonics, erosion & deposition, & rocks Several different classification schemes for.

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