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

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

3. Sea Level, Coastal Geomorphology

4. 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.

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

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

7. 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

10. 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

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

12. 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

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

16. New Jerseyfication

17. Beach "Nourishment"

18. 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)

19. Chesapeake Bay - the drowned valley of the Susquehanna River

20. Fjorded Coast of Southwest New Zealand

21. 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

22. Northern California has an Emergent Coastline due to tectonic uplift

23. Wave-cut Marine Terraces near Fort Ross, California23

24. 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

25. The Fall Line divides the Coastal Plain from the Piedmont

26. 1,500,000
1,000,000
500,000
30,000
4,000