In revisiting moderate hikes that I often repeat, one morning this week I returned to the Kelley Trail. I drove out Route 113A from Tamworth Village and just after the Wonalancet Chapel, turned right into Ferncroft. In the hiker parking lot was one car with Massachusetts plates and an icy windshield, perhaps winter campers.
I headed up the Old Mast Road and bore right on the Kelley Trail. Entering a logging road, the trail bore right down the road for a 10th of a mile. Then at a small sign in a tree on the left, I followed the trail back into the woods with the sound of a nearby stream through the trees.
I followed it up the west side of a steep ravine with the stream gurgling far below. Then it turned way from the stream on gentler terrain, only to return to it at the head of the ravine, and cross to the east side. I was approaching a small box canyon that makes the Kelley Trail unique.
The story of this canyon began 12 to 15,000 years ago at the end of the last ice age. Further north, beyond the ridge above and in the wide Albany Intervales where the Kancamagus Highway is today, a young Swift River came down out of the mountains and filled up the valley with water — the post glacial Lake Albany. At the narrows approaching the Conway area, a plug of glacial debris blocked the water from spilling forth that way. This plug was mostly comprised of rocks and gravel, with chunks of ice mixed in.
The banks of Lake Albany rose higher and higher, eventually spilling over low spots, such as Paugus Pass on the ridge above ravine where the Kelley Trail is located today. For a few decades, a torrent of water spilled over there, gouging out the small box canyon and the steep ravine below it.
Meanwhile further east at the narrows, water seeped into the debris of the plug, slowly turning it to mud. The ice blocks mixed in also melted, loosening up the material more. Eventually it burst, spewing down the narrows and spilling out into the valley below. If one drilled or dug in the Conway Village area today, where the most common material would be the sand and clay of flood plains, a chaotic deposit of coarse stony dirt would likely be found from that sudden release.
This process was related to me by the geologist Brian Fowler of Madison. He also mentioned a classic example out west of such dam releases that occurred periodically from the same lake. Post glacial Lake Missoula on the Clark Fork River was much bigger than Lake Albany. It was the size of a small Great Lake. It had various enormous debris dams. When these burst periodically, water spilled out across eastern Washington, scouring off topsoil. Today that wide area is called the Scablands. These individual floods all continued down the Colombia River Gorge.
Back to my recent hike up the Kelley Trail, in the narrowing canyon the trail began to go directly up the rocky stream bed, any water invisible below the rocks. At one point it widened into what was known by early Wonalancet Outdoor Club members as the "Pleistocene Plunge Pool," a "bowl shaped remnant of an Ice Age waterfall."
Then after a short climb out of the canyon, the trail followed a more gentle dry V-shaped stream bed to Paugus Pass on the ridge top. I turned left there on the Lawrence Trail and in 0.3 miles reached "Four Way" junction, where I bore left again down the Old Mast Road, reaching the parking lot and my car and making for a very pleasant 4.6 mile loop.
There are no outward view points on this loop. That may seem like a limitation, but when you are passing the Pleistocene Plunge Pool on a drizzly day, there will likely be little desire for an outward view.