A GEOLOGIC HISTORY

FLORIDA’S BARRIER ISLANDS

http://www.fishstock.com/sites/fishstock.com/files/images/2014/03/A01N913287.jpg

BARRIER ISLAND FORMATION

1. Offshore bar theory

2. Spit accretion theory

3. Submergence theory

(http://coast.noaa.gov/archived/beachnourishment/html/geo/barrier.htm?redirect=301ocm)

(http://upload.wikimedia.org/wikipedia/commons/thumb/4/48/Accreting_coast_Image6.svg/360px-Accreting_coast_Image6.svg.png)

(USGS)

BARRIER ISLAND ANATOMY

http://faculty.scf.edu/rizkf/OCE1001/Images/estuarytypes.jpg

(a) Coastal plain: Chesapeake Bay- drowned river valley

(b) Fjord: Puget Sound- glaciers

(c) Bar-built: IRL Barrier Islands

(d) Tectonic: San Francisco Bay- San Andreas faulthttp://en.wikipedia.org/wiki/Estuary

CHANGING COASTLINES

Coastline changes with sea level

and global temperatures

http://www.fnai.org/ARROW/almanac/geology/geology_history.cfm

CAUSES OF EARTH’S TEMPERATURE FLUCTUATIONS

• Moving continents affect oceanic and atmospheric circulation

• CO2 concentrations (high CO2 => high temp)• Volcanic eruptions, extraterrestrial collisions

(dust reflects sunlight => low temp)• Milankovitch cycles

• Eccentricity• How elliptical the orbit is

• Axial tilt (obliquity)• Diff btw orbital and rotational axis

• Precession- axis wobbles like a spinning top• 26,000 year cycle

• Seasons- small scale• Relates to tilt and not distance from

sunhttp://en.wikipedia.org/wiki/Milankovitch_cycles

http://en.wikipedia.org/wiki/Milankovitch_cycles

Circular orbit, no eccentricity

Orbit with 0.5 eccentricity.

precession

obliquity

http://en.wikipedia.org/wiki/Milankovitch_cycles

http://www.johnenglander.net/sea-level-rise-blog/why-sea-level-will-rise-centuries-ultimately-100-feet

TECTONIC PLATE MOVEMENT AND

FORMATION OF FLORIDA• Plates can move up to 10cm/yr!• Driven by convection currents deep

underground that either create or destroy Earth’s crust

http://en.wikipedia.org/wiki/Plate_tectonicshttp://www.ucmp.berkeley.edu/education/dynamic/session1/sess1_earthcurrents.html

http://upload.wikimedia.org/wikipedia/commons/8/8a/Plates_tect2_en.svg

TECTONIC PLATE MOVEMENT AND

FORMATION OF FLORIDA

• Mid Atlantic Ridge created Atlantic ocean• Was a factor in the separation of Pangea

• Crust being created, pushed land apart, gave east coast N. America sloping beaches, while the west coast slides over another plate, creating cliffed beaches

http://www.amnh.org/education/resources/rfl/web/bulletins/earth/A/6/4/A_0007_04_00_w_image1_lg.jpg

HOW OLD ARE FLORIDA’S BARRIER ISLANDS?

• About 18,000 years young• End of the Pleistocene • Last glacial melting period • Susceptible to frequent changes• Human and environment influenced

http://fcit.usf.edu/florida/teacher/science/mod2/resources/changing.coastlines.pdf

http://tracks.roojoom.com/u/shirly-ronen-harel,60/the-geological-time-scale-explained,3979

GEOLOGIC TIME SCALE

HURRICANE CHARLEY EROSION

NSB INLET MARCH 2014