Double Treat EarthCache
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Located on shore of the Gulf of Maine on the road to Pinkneys Point. You must go at low tide to observe one of the features. Public access general use field and parking area on land side of the beach. Use site coodinates; can’t miss it. Wear solid shoes.
A common tenet of geomorphology, the study of land forms, is that the lands forms we observe are the result of an interaction between materials available and the physical processes involved in moving or shaping them. That is form = material + process. For example, given sand as a beach material, high energy waves, as in a winter storm, will produce a steeper beach profile (form) than the same sand being processed by low energy waves, such as we might find in the summer. Understanding the concept of the form, material, process equation helps us to observer and better understand the world of land forms about us.
This idea is well illustrated in Double Treat - the happy meeting of a glacial Drumlin and a more recently formed Tombolo.
Based on the description in Wikipedia, a DRUMLIN is an elongated whale-shaped hill formed by glacial action. Its long axis is parallel with the movement of the ice with the blunter end facing into the glacial movement. Drumlins frequently occur in drumlin fields and this is true of the many drumlins in southwest Nova Scotia and Yarmouth County.
The drumlin we observe here is an off-shore feature formed at the end of the Last Wisconsin ice age, about 10,000 years ago. At that time the sea level was much lower than it is now so it would have been sitting on dry land. As sea level rose it surrounded the feature we observe today. Its form is the result of process of glaciation and the availability of glacial till, a collection of stone and gravel picked up as the glacier scoured the land surface. According to Wikipedia, there are many theories as to the exact mode of origin.
The presence of the drumlin off-shore is responsible for the more recently (in relative terms) formed TOMBOLO, which is a depositional spit or bar which forms as a narrow piece of land between an island (the drumlin in this case) and a mainshore beach. Our tombolo is only visible at low tide which is why you need to visit it at that time. The waves at this location roll in mostly from the west, parallel to the general trend of the coast you can see looking south. When these waves hit the drumlin they are refracted, that is, they bend around the drumlin depositing sand and stone (shingle) moved by longshore drift in each direction around the island to where the waves meet and form a ridge of material.
Thus, to form a tombolo, we need sand and shingle as materials which are very common in this coastal setting. However we need a process of wave refraction, as caused by the drumlin, to form the tombolo. Without the drumlin the sand and shingle would just end up parallel to the shoreline. There is a good chance that the drumlin has also supplied much of the material in the tombolo.
What you need to provide in order to log,
Do not answer in cache page, except for #1.
#1. You must photograph the exposed tombolo and drumlin with GPS in the scene. Informative shots including refracted waves, materials or things you found interesting about the formations are encouraged.
#2. What is happening at the south end of the drumlin and what are the clues that lead you to that observation?
#3. If sea level continues at its present level or rises, what do you predict will happen to this drumlin?
#4. What can you tell me about the wave energy dynamics that are forming the tombolo? How do you know this?
#5. You are observing the tombolo at low tide at 15:00 hours today. What time time tomorrow afternoon would you suggest your friend visit to see it at the same state?
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