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

Fjords Greenland Fjords Nasa image Norway Nasa image

Drowned River Mouths Long Island, New York Cape Cod, Mass Nasa Image

Chesapeake Bay Nasa image Delaware Bay Nasa 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, and bottomset beds

Sacramento River Delta NASA

Ganges River

Nile River

Deltas Mississippi Delta, Nasa image Nile Delta Nasa 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 Coasts Central Oregon Western Sahara, Nasa Image Flickr.com

Santa Maria

Los Angeles Airport

Volcanic Activity, Kilauea, Hawaii 2005 MSNBC

Fault Coasts Point Reyes, CA Nasa Image Red Sea Nasa 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 Dover Cliff, England Santa Barbara Sylvester, UCSB BBC El Matador Beach, Malibu rockcitynews.com

Barrier Islands North Carolina gpb.org Galveston, Texas gpb.org

Sand Spit, Mississippi River, 1954 H. N. Fisk, E. McFarlan, Jr., C. R

Reefs and Atolls Great Barrier Reef, Australia Nasa image Atafu Atoll, Tokelau, Southern Pacific Ocean Nasa image