On a recent visit to the Trinity area I had the opportunity to hike this trail and seek out the very old nearby Fox Island cache. It was while on this hike I noticed this Double Tombolo??? Could it be possible? Later, after my hike I did a little research into this geological formation to see how common this formation might be.
Turns out that it isn't as common as you might think. While there are a few notable Double Tombolos in the world, I have never seen one in our province. Maybe there are more. Maybe this one might get other geocachers to seek out more of these geological formations around our province.
According to Wikipedia:
"A tombolo is a sandy isthmus. A tombolo, from the Italian tombolo, meaning 'pillow' or 'cushion', and sometimes translated as ayre, is a deposition landform by which an island becomes attached to the mainland by a narrow piece of land such as a spit or bar. Once attached, the island is then known as a tied island.
Several islands tied together by bars which rise above the water level are called a tombolo cluster. Two or more tombolos may form an enclosure (called a lagoon) that can eventually fill with sediment."
Wave Refraction and Defraction:
True tombolos are formed by wave refraction and diffraction. As waves near an island, they are slowed by the shallow water surrounding it. These waves then bend around the island to the opposite side as they approach. The wave pattern created by this water movement causes a convergence of longshore drift on the opposite side of the island. The beach sediments that are moving by lateral transport on the lee side of the island will accumulate there, conforming to the shape of the wave pattern. In other words, the waves sweep sediment together from both sides. Eventually, when enough sediment has built up, the beach shoreline, known as a spit, will connect with an island and form a tombolo.
Unidirectional Longshore Drift:
In the case of longshore drift due to an oblique wave direction, the flow of material is along the coast in a movement which is not determined by wave diffraction around the now tied island, which it has reached. While the strip of beach material connected to the island may be technically called a tombolo because it links the island to the land, it is better thought of in terms of its formation as a spit, because the sand or shingle ridge is parallel rather than at right angles to the coast.
It seems that this is what we may have here at this location!! Two Tombolos that have created a water fiilled enclosure, or lagoon.
To get to this cache you will have to hike the Fox Isalnd trail system. It is rated at a easy to Moderate trail. The shoreline views along the way are well worth the hike. Return trip is approx 50-60 minutes depending on your hiking pace and breaks along the way.
Your task, in order to claim the find on this Earthcache, is to find the answers to the following questions:
1. Estimate the total length and width of the entire double Tombolo formation.
2. Are the rocky beach's on each Tombolo different or the same? Explain in your own words why you think so.
3. How do you think this particular Double Tombolo was formed? In other words why was a "Double" formed instead of a "Single" Tobolo?
4. Post a picture of youself or your GPS at the location of this Earthcache.