A tombolo is a sandbar that connects an island to the mainland. Tombolos are formed when the wave refraction off two landmasses (the island and the mainland) is such that sand and other sediments (solid fragments of organic or inorganic materials that come from weathered rock and transported by wind, water, or ice) are deposited between them and build up faster than they can be removed. Over time, these sediments form a ridge that eventually becomes higher in elevation than sea level and connects the island to the mainland at all tides. Once attached, the island becomes known as a tied island.
From the coordinates given, two tombolos are visible. First, to the east, is a narrow strip of land that connects the former island of Biddeford Pool to the mainland. The land on which the roadway and beach houses sit is comprised completely of sediments. If you drive down to the village of Biddeford Pool, you will see that where Milestretch Road makes a 90 degree turn to become Lester B. Orcutt Boulevard (N 43 26.746 W 070 21.102 degrees) there is a noticeable difference in the terrain. This is because the island is formed from bedrock (solid, unweathered rock) and not sediments.
Second, to the north, is a narrow strip of land that connects the former island of Fort Hill at Hill's Beach to the mainland. Across the tidal inlet, houses can be seen on the strip of land that was built from the deposition of sediments. The former island of Fort Hill is also visible across the tidal inlet (Biddeford Pool).
These tombolos are unique in that the two together enclose a tidal pool (Biddeford Pool) open to Saco Bay only through a tiny passageway known to locals as “The Gut.” This tidal pool is extremely shallow and is almost completely dry at low tide. Eventually, Biddeford Pool may become completely filled with sediment.
The coastal region of Biddeford is also unique in that two other tombolos are currently forming. These are visible off the coast of Hills Beach from the coordinates of N 43 27.001 W 070 21.541 degrees. A sand bar connects Basket Island to the mainland at low tide. This island is the summer home for eight families who have permits to drive their vehicles across the sand bar. The other sand bar connects Stage Island (the one with the monument) to Basket Island. While these islands are currently only connected to the mainland at low tide, there will eventually come a time when they are connected at all tides.
To log this Earthcache:
Send an email with answers to the following questions to me via my profile page. Please do not reveal any of the answers in your log. The email must be received within a couple of days of logging your find. Any logs not accompanied by an email will be deleted. Also, all geocachers must send their own email to get credit for this find. Do not state in your log that another geocacher is emailing the answers for you because your find will be deleted.
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Label your email as “Biddeford Tombolos.”
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State the date, exact time, and tidal phase during your visit.
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While standing at the coordinates and looking across the water, describe any observations that provide evidence that the two landmasses described above are tombolos. Think about the definition of a tombolo provided and base your evidence from that.
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Describe the sediment size near the water's edge on either side of the bridge on which you stand. Would you describe this sediment as sand (small particles approximately 0.0025 to 0.079 inches), gravel (slightly larger particles approximately 0.079 to 2.5 inches), or cobbles (2.5 to 10 inches in diameter)?
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Turn around 180 degrees and look at the terrain on the opposite side of the bridge. How would you classify this terrain?
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Walk across the street to the second waypoint at N 43 26.172 W 070 22.107 degrees. From these coordinates, describe this side of the tombolo. What is the sediment size in this location (sand, gravel, or cobbles)? How does this side differ from the interior side?
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Optional: Post a photo of yourself and your GPS at the original coordinates with one or both of the tombolos in the background.
Thank you for completing this Earthcache. This area is one of the most beautiful locations along the coast of Maine, so enjoy your visit!