Introduction to Coastal Process

Introduction  ½ world’s population in coastal regions  Coastal modification impacts humans and other organisms/plants  Present-day climate change will modify coasts LA Times

Class Focus  Shaping of Coastline  Processes operating on coastline  Changes along the coast

More Specific Class Focus  Geology influence on coastal features  Nearshore processes  Fluvial processes  Sea level and climate  Sediment transport

Some Terminology  Shore  Zone between low tide level & upper level of wave action. In our coasts, usually cliffs  Consists of foreshore, backshore, and nearshore

Terminology  Shoreline  Water’s edge  Beach  Loose sediment (sand, gravel, boulders) accumulation  Mostly in backshore  Coast  Includes shores & nearshore to where waves break  Inland to where marine influences cease—cliffs, lagoons etc  Will vary in width  Where air, sea, water mix  Influenced by  Tectonics and lithology  Oceanographic processes—waves, tides, current  Sea level  Atmospheric processes—wind, precipitation  Coasts shaped by  Erosion  Deposition

Ancient Coastlines  Sedimentary geologists  Reconstruct sedimentary environments  Ancient shorelines preserved throughout rock record  Help reconstruct ancient sea level rise and fall  Global record vs local record  Climate vs tectonic activity Oysters, Vaqueros Fm. Picasaweb.com

Shape of coastlines  Straight or curved  E.g. san Andreas Fault in San Francisco area  Madura, Indonesia  East Madagascar Based on U.S. Geological Survey map

Terminology  Coastline  Land margin at normal high tide  Difference between coastline and shoreline?

Straight Coastlines  Madagasgar  Indonesia

Some basic relationships  Headlands & promitories= resistant rocks  Bays = less resistant rock or tectonic folding, tilting  Embayed coastline with valley mouth usually submerged  E.g. east U.S. coast  Gulf coast formed by deposition = curved coast Marin Headlands, San Francisco area Photo (c) Andrew Alden

Gulf coast and Eastern Seaboard NASA ECB.org

Rounded Bays  Submerged volcanoes  E.g. Santorini  Hanauma Bay, Oahu Hanauma Bay and Koko Crater at Koko Head, Oahu NASA

Evolution of Coasts  Tectonic Processes  Separation of plates  Active tectonic processes—faulting and folding  Climate—wind, rain, weathering & decomposition, vegetation  Rising and falling tides

Changing Coastline  Advancing  Sedimentation is greater than erosion  Emergence, uplift, sea level fall  Retreating  Erosion greater than deposition  Sea level rise  subsidence

Rates of Coastline Change  Rapid  Storms  Lava flows  Earthquakes  Gradual  Longer termed changes  Tectonic uplift, sea level rise  Measure changing coastline  Maps, photographs, gps, etc.