Watkins Glen State Park, New York
Google Earth view looking upstream, eastward, from Watkins Glen.
Geology of Watkins Glen State Park
Surficial geologic map of the Watkins Glen area. Glen Creek cuts across glacial gravels and down through the ancient bedrock. Glacial deposits are orange, light pink, purple, and brownish orange, and are made of gravel. The red pattern is the bedrock seen in the canyon. The olive color around Seneca Lake is river deposits.
During the last ice age, this area was covered by the continental ice sheet flowing southeastward out of Canada. Where the ice was able to carry sediments and loose bedrock away, it carved out the 11 Finger Lakes.
Contrary to popular thought, glaciers are not like "bulldozers" -- they are not dense enough to push large amounts of sediment and rock. Instead, they are very effective conveyor belts that drag material along their bottoms. When the ice pauses in one place, the ice continues to move in the conveyor, but the ice melts away only at the stationary end. That forms piles of gravel known as "moraines," the gravelly hills in this part of New York.
After the finger glacier dug out the valley for Seneca Lake, the stream at Watkins Glen was left high above the new valley. As a result, a series of waterfalls formed at the east end near modern Watkins Glen, and erosion progressed westward, deepening the gorge as waterfalls steadily collapsed and moved upstream. This process is called "headward erosion," and is how all canyons and gorges form. Because this gorge is relatively young, only starting 12,000 years ago, we can still see headward erosion taking place wherever there's a waterfall or ledge.
The photos below start at the stone pavillion ("you are here" on the map above) and proceed upstream on the south side trails and then back downstream on the north side trails.
The old stone pavillion is made of the local bedrock siltstone, seen here on the back side of the structure.
Looking closely, you can see "plumose structures" where the stones were split. They're the feather-like patterns on the siltstone. They originate where the hammer or chisel struck the rock, and spread outward.
Starting near the top (the west end), you'll go deeper and deeper into the gorge with great views of the layered sedimentary rocks, the stream cutting its narrow channel, and the winding trail.
Watkins Glen is all about the interaction of the stream with the thinly bedded sedimentary rocks and the natural fractures, seen here. The fractures (joints) tend to erode faster than the solid rock, and form most of the ledges in the streambed.
These sedimentary layers are mostly silstone and sandstone that were eroded off the huge "Acadian" mountains that formed when North America collided with Europe to form Pangea, beginning about 335 million years ago. The sediments were deposited westward into a warm tropical sea by rivers and streams.
Looking upstream here, you can see the fractures forming little ledges in the streambed.
Where water has pours over a ledge into one spot for a long time (centuries or longer), sand and gravel in the stream swirl around and dig holes like this one. In the gorge, you'll see old and new potholes.
The path takes you under waterfalls in several places. On a hot day, that's a great relief!
This section is a series of potholes that are eroding today.
You'll enjoy how the path is carved right into the sedimentary layers, giving you fantastic close-up views of the gorge.
These sedimentary layers were deposited by slow stream currents into a shallow tropical sea. You can see the effects of those currents in the cross-bedding, just as you would see in modern sediments.
Thicker layers represent periods of more rapid sediment deposition, or in some cases slower deposition over longer times. This layering shows you how the sea's environment changed in cycles.
There are few places you could ever visit that have a more narrow gorge.
I lost count of the waterfalls here! Each one invites you to pause, enjoy, and ponder. Over time, each waterfall undermines itself, the bedrock falls off, and the stream gradually moves upstream.
Down the east end you'll find this bridge. Don't worry, you won't find Shelob in the tunnel at the other end! (Lord of the Rings reference)
At the west end, the gorge opens up to the town of Watkins Glen. This is where a finger of the ice sheet flowed down the broad valley until 12,000 years ago. The stream has been deepening the gorge ever since.
