4Shoreline Change Shorelines are always changing Shorelines change on many time scales:very short, hours to days (hurricanes, northeasters)intermediate, years to decades (“normal” coastal erosion, deposition)long term, hundreds to thousands of years (sea level change, erosion of hard rocky coasts)These changes affect both natural and man- made features.
5Shoreline Change Erosion of the sea stack at Nye Beach, Newport, OR 1890191019701990
6Shoreline ChangeBeach erosion at Saint George Island near Appalachicola, FL destroyed Cape Saint George Lighthouse, built in 18521940s20041999
7Coastal Erosion - horizontal retreat of the shoreline at rates of up to 8 m/yr on some barrier islands. Average rates range from 5-50 cm/yr
10Sea Level Rise will have the greatest effect on low, tectonically passive coastlines because that is where the shoreline will shift the furthest distance inland
11Tectonic Uplift in the past 21,000 years has been greatest in regions which are rebounding from the weight of the melting ice sheets.
12Shoreline "Stabilization" Coastal communities frequently use hard stabilization to attempt to protect property from coastal erosionJetties extend into the ocean at the entrances to rivers and harborsGroins are built perpendicular to the beach to trap sand transported parallel to shoreBreakwaters are built offshore parallel to the shoreline to create a quite water zoneSeawalls are built along the beach parallel to the shoreline to protect individual properties
21Emergent CoastlinesCoastlines where previously submerged shoreface offshore sediments are becoming "subaerial" due toTectonic UpliftRapid Withdrawal of Water by Global GlaciationRaised BeachesRaised Wave-Cut PlatformsCaves or Valleys with mouths that "hang" above present sea level
22Northern California has an Emergent Coastline due to tectonic uplift
23Wave-cut Marine Terraces near Fort Ross, California 23
24Continental shelf - beveled surface that was dry land for several periods in the past 66 million yearsContinental slope - gradually dipping at less than 10 degrees towardContinental rise - sediment mostly mud and microorganisms that settled out of seawater
25The Fall Line divides the Coastal Plain from the Piedmont