The Giant's Kettles of Bulls Bridge EarthCache
The Giant's Kettles of Bulls Bridge
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***Congrats to nmctwx for FTF***In Gaylordsville, south of Kent, off Rt. 7, take Bulls Bridge Road to the parking area across the covered bridge; open dawn to dusk. From the parking area go to the river just above the bridge (west side) and down the steps on the bank. Caution should be used near the water, especially with young children. The banks and rocks are often slippery and this section of the river is filled with rapids. During one of my visits the river was running at almost 10,000 cfs.
Welcome to Bulls Bridge Scenic Area, where you can hike, geocache, white-water kayak, fish, or just sit and enjoy the beautiful surroundings, which includes an old covered bridge crossing the Housatonic River.
The Housatonic River has been around for millions of years, and began as a straight-flowing river originating in upper New York State, until erosion gradually changed the landscape and the Hudson River took over the headwaters, leaving the Housatonic's origin in western Massachusetts, near Pittsfield. Much of the Housatonic river basin is made up of gneiss and schist, but some portions in Connecticut contain marble, a softer rock formed from limestone. Evidence of this can be seen at Kent Falls State Park. As the glaciers advanced and receded, the course of the river was constantly changed, most easily in the softer marble areas, and resulted in the river as we know it today. However, from Gaylordsville to just north of New Milford, it passes through the much harder rock, gneiss.
Where are the Giant's Kettles? They should be right at your feet; in other words, glacial potholes. Although there are many more examples upstream and downstream, I chose this particular spot because it (most likely) will be accessible even during times of high water. At lower water levels you may be able to see more examples nearby, particularly upriver a hundred yards on the same side(see photo).
So, how were they formed? As you can guess, it didn't happen overnight. About 13,000 years ago a mile-thick glacier covered CT and all of New England. As it receded, the melting waters formed rushing streams and rivers, which carried many stones and pebbles left by the glacier. Sometimes, small stones (called "grinders")would find a crack in the bedrock and, though trapped, continued to move and swirl about, pushed by the force of the water, making these cavities wider and deeper over thousands of years; see illustrations 1 & 2 below. Careful observation of some potholes may reveal gouges on the inside walls due to uneven wear.
To demonstrate, place a small stone into a container and apply a jet of water using a faucet or hose. Note that the force of the water will cause the stone to move about, trying to escape its confined space.
In order to take credit for this cache you must email me the answers to the following questions:
#1. At this location, look for two potholes very close to each other; one is fairly circular and the other is oblong; both had short, stalky plants growing out of them at the time. Measure the longest dimension of the oblong one (if you don't have a measuring tool, use something else, such as a hiking pole, rope, etc. and mark it so you can measure it at home); is it closest to:
a. 24 inches
b. 48 inches
c. 72 inches
#2. How do you think this particular pothole attained its present shape?
#3. The bedrock you are standing on is gneiss (nice), a fairly common, hard, metamorphic (heat and pressure) rock. Based on what you have learned, what conclusion can you draw about one characteristic, or property, of the small stones that carved out the potholes in the gneiss?
You may post your find online prior to emailing, but I reserve the right to remove logs with inadequate or incorrect answers. Photos can no longer be used for proof of visiting, but are welcomed and encouraged. If you would like to see a really big pothole, visit Archbald Pothole State Park in northeastern Pennsylvania, where the pothole is 38 feet deep and 42 feet wide! I hope you enjoy this beautiful location.
Sources:
Wikipedia, (visit link)
Giant's Kettle (visit link)
The Ice Age in Connecticut (visit link)
HVA, Geologic Description of the Housatonic River
(visit link)
The Face of Connecticut by Michael Bell (visit link)
NYC Regional Geology, Kent Falls State Park (visit link)
Additional Hints
(No hints available.)