Sable Island EarthCache
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The Graveyard of the Atlantic.
Note: Access to Sable Island is controlled by Parks Canada. Details on requirements for access can found on this web site -http://www.pc.gc.ca/eng/pn-np/ns/sable/index.aspx
Southeast of Nova Scotia is a section of the Continental Shelf known as the Scotia Shelf. It's about 700 Km in length and varies between 120 to 240 Km in width. It's depth averages about 90 m. During the last ice age, about 11,000 years ago, there were areas of dry land separated by deep basins and channels. When the glaciers retreated and sea levels rose the only remaining dry land was Sable Island located about 160 Km Southeast of Nova Scotia. In area the island is about 1.5 Km wide and 40 Km long.
Sable Island has caused over 350 recorded shipwrecks due to its location on the shipping route from Europe to the Americas. This has given it the name "Graveyard of the Atlantic".
Sable Island's most famous fauna are the wild horses which number from 200 to 350. The horses are descendants of domestic animals brought to the island during the late 1700s to the early 1900s. The horse population is unique because it is not managed and not subject to interference. Sable Island is also home to numerous sea birds, the Ispwich Savannah Sparrow and the world’s largest congregation of Grey Seals.
Geological features include sand dunes and beach sands. The beach sands often extend to a depth of 300 m below the surface. Most of the island's surface is a series of dunes and beaches composed entirely of sand with very little organic content. Scattered layers of soil and peat can be found at various depths. The island has survived because of the binding effects and protective nature of the plants, especially Marram grass.
A ground water reservoir spans the entire length of the island. This reservoir exists due to the high permeability of the prominent surficial sands. Streams are not present on the island although freshwater ponds exist. The water table is generally flat with a slight concave geometry and a slope from the center to each shore.
The technical term for a water table underlying sand is a "Surficial aquifer". This type of aquifer is usually shallow with a thickness typically less than 15 m. The groundwater is unconfined and moves along the hydraulic gradient to areas of discharge. Surficial aquifers are recharged as the water table responds to precipitation/snowmelt. Besides precipitation/snowmelt, the only other source of groundwater recharge are the freshwater ponds.The water level in these ponds fluctuates 0.9 to 1.2 m a year. Their depth is usually about 1.5 to 3.0 m. They are well protected from sea water by the dunes.
The freshwater pond in the picture is bordered by tall sand banks. The hydraulic conductivity ability of the sand results in a high water table which gives way to many ponds.
In order to log this Earthcache, please do the following:
1. Post a picture of you and/or your GPS at the posted coordinates with the pond in the background.
2. Post your estimate of the area encompassed by the pond.
3. Post the number of freshwater ponds you observe as you explore the island.
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