Rise of Anna Maria EarthCache
Hidden : 5/7/2017
Difficulty:
2 out of 5
Terrain:
1.5 out of 5

Size: Size: other (other)

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Geocache Description:

Rise of Anna Maria Earthcache

IMPORTANT: This Earthcache will bring you to the historic Anna Maria Pier. There is ample parking nearby and access to the earthcache site is by foot.

Barrier Islands.
Barrier islands make up more than 700 miles of Florida’s coastline. They are typically elongate, low-lying islands occurring in linear chains parallel to the coastline separated by tidal inlets. Barrier islands are naturally formed by shifting sands that build upon an existing sandbar to eventually form an island. Specifically, the barriers formed as the result of a gentle wave climate transporting sediment (sand) to shallow water and shoaling upward to intertidal (between regular low/high tide) and eventually supratidal (exceptional tides or by tides augmented by a storm surge) conditions. The position of the barriers are aided by antecedent topography produced by the shallow Miocene limestone bedrock. The two most important variables that control barrier island development along the coast are the availability of sediment and the interaction of wave and tidal energy. A third important factor in the formation of barrier islands is a wide gently sloping inner shelf (a gradual decent of the underlying seafloor as you move out to the open water).

Barrier islands are active and are constantly being shaped by erosion (removal of sand from a beach), storms, accretion (addition of sand to a beach) and the natural drift of sand along the coast. Beach erosion and accretion are caused by ocean currents, wave action and changes in the sea level. Barrier islands are greatly affected by the forces of wind and waves and are constantly moving towards or away from the mainland. Because barrier islands provide mainland protection from hurricanes and large storms by absorbing the impact of waves and storm water over flow, entire barrier islands can be severely reshaped or completely destroyed by a major storm.


Anna Maria Island.
Anna Maria Island is a drumstick barrier island that is the first barrier south of the expansive mouth of Tampa Bay. The northern portion of the island formed around 3,000 years ago (making it is one of the oldest barrier islands) and has extended itself to the south only in the past few hundred years. The image to the right depicts a sequence of paleogeographic maps of Anna Maria Island showing various stages of development from about 3,000 YBP to the present. Anna Maria Island drumstick barrier is characteristic of mixed wave and tidal energy. Miocene bedrock has been shown to be at a depth of about 11 to 12 m below the northern part of the island. Beach, nearshore, and dune deposits represent the island composition and are characterized by well-sorted sand and shelly sand.


References.
S.D. Locker, et al., 1999. West-Central Florida Coastal Transect # 6: Anna Maria Island. U.S. Geological Survey Open-File Report 99-510.
Pekala, John M., 1996. Stratigraphy and geologic history of Anna Maria Island, Manatee County Florida: Master's Thesis, University of South Florida, Tampa, FL.

In order to log this Earthcache, you must email / message team wiji (see profile) the answers to the following questions:

1. At the posted coordinates, do you see evidence of the two most important variables that are required for barrier island development? Hint: The variables you are looking for are described in the text above. How do these two variables interact in the formation of Anna Maria Island?

2. To appreciate the third variable (a gently sloping inner shelf), let's take a walk along the pier. Estimate the distance from shore where you can see to the bottom of the water (the sea floor)? Based on your measurement, how do you think this impacts barrier island formation?

3. How do you think a 1 ft rise in overall sea level would affect barrier island formation and the overall shape of Anna Maria Island?

4. OPTIONAL - Take a photo of your GPSr or yourself/team on the Anna Maria Pier. You may include this photo in your log.

++ Congratulations to Grand Illusion Crew on the FTF!! ++

www.essexcountygeocachers.org

This cache was placed and is maintained by an essexcountygeocachers.org member.

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