Quaternary Geomorphology A Workshop for P.G. Candidates December 18, 2010 Dr. Don Thieme 1

Geochronology, Glacial Intervals, Isotopic Dating, etc... Glacial Landforms and Sedimentary Deposits Soil Classification and Paleosols Sea Level and Coastal Geomorphology

Sea Level, Coastal Geomorphology

Shoreline 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.

Shoreline Change Erosion of the sea stack at Nye Beach, Newport, OR 1890 1910 1970 1990

Shoreline Change Beach erosion at Saint George Island near Appalachicola, FL destroyed Cape Saint George Lighthouse, built in 1852 1940s 2004 1999

Coastal 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

Sea Level Rise will have the greatest effect on low, tectonically passive coastlines because that is where the shoreline will shift the furthest distance inland

Tectonic Uplift in the past 21,000 years has been greatest in regions which are rebounding from the weight of the melting ice sheets.

Shoreline "Stabilization" Coastal communities frequently use hard stabilization to attempt to protect property from coastal erosion Jetties extend into the ocean at the entrances to rivers and harbors Groins are built perpendicular to the beach to trap sand transported parallel to shore Breakwaters are built offshore parallel to the shoreline to create a quite water zone Seawalls are built along the beach parallel to the shoreline to protect individual properties

Groins along the New Jersey shore at Cape May Which direction is the longshore drift?

New Jerseyfication

Beach "Nourishment"

Submergent Coastlines Coastlines that have been inundated due to a relative rise in sea level Drowned River Valleys (rias) become estuaries Drowned Glacial Troughs (fjords)

Chesapeake Bay - the drowned valley of the Susquehanna River

Fjorded Coast of Southwest New Zealand

Emergent Coastlines Coastlines where previously submerged shoreface offshore sediments are becoming "subaerial" due to Tectonic Uplift Rapid Withdrawal of Water by Global Glaciation Raised Beaches Raised Wave-Cut Platforms Caves or Valleys with mouths that "hang" above present sea level

Northern California has an Emergent Coastline due to tectonic uplift

Wave-cut Marine Terraces near Fort Ross, California 23

Continental shelf - beveled surface that was dry land for several periods in the past 66 million years Continental slope - gradually dipping at less than 10 degrees toward Continental rise - sediment mostly mud and microorganisms that settled out of seawater

The Fall Line divides the Coastal Plain from the Piedmont

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