When trying to understand and appreciate any present-day geological formation, you have begin with understanding the rocks that the formation is made of. The history of the rocks gives you context for how erosional forces ultimately created the formation in question, and understanding the gorge at Watkins Glen State Park is no different. In a quick-and-dirty summary, fine-grained sediments were deposited in a shallow sea, and these sediments formed a thick layer of a soft rock called shale. Large-scale tectonic forces then exerted pressure on this shale layer, creating thousands of fractures called joints. These joints represent weak areas in the shale, and when glacial and post-glacial forces met these joints, water was able to easily erode the shale and cut a deep gorge over the time span of several thousand years.
|Map courtesy of Woudloper, from Wikimedia Commons.|
|Map courtesy of Dennis C. Murphy via The Devonian Times.|
Many of the sediments that were deposited in the Catskill Delta—especially the area that would become western New York—were fine-grained (i.e. small). These fine-grained sediments eventually became fine-grained rocks like shale and siltstone, although there are some thinner layers of limestone and sandstone mixed in as well. The rock layers of the Catskill Delta are incredibly thick, ranging from several hundred feet thick to several thousand feet thick, depending on your location. This large formation is subdivided into smaller layers, and the rocks that are exposed at Watkins Glen State Park belong to a specific slice of the Catskill Delta formation called the Genesee Group.
As the Permian Period began around 300 million years ago, another orogeny took place. This orogeny—termed as either the Appalachian or Alleghenian Orogeny—occurred as Gondwana (specifically the part of Gondwana that would become Africa) collided with Euramerica (the continent that was made of Laurentia plus the newly acquired Avalonia and Baltica from the Acadian Orogeny). A giant mountain range was formed that included the Appalachian Mountains, Ouachita Mountains, Atlas Mountains, and several other associated ranges. The ocean that used to separate Gondwana and Euramerica was also closed up during this orogeny. The resulting Euramerica-Gondwana landmass is known today as Pangea, a name many of you have undoubtedly heard.
|The dissected Allegheny Plateau.|
|Map adapted from Google Maps.|
Beginning around 2.5 million years ago, the Earth began a cyclical period of cooling, and a large ice sheet formed at the North Pole. Thus began the Pleistocene Ice Age. During this ice age, the polar ice sheet advanced and retreated in a cyclical fashion nearly two dozen times. Each time this ice sheet advanced southward, it would travel up those north-south running valleys in western New York, making them wider and deeper.
|Remnants of the hanging valley carved by Glen Creek as it empties out into the main Seneca Valley. The valley no longer "hangs" above Seneca Valley.|
When it comes to liquid water, it’s really important to know that gravity is forcing water to travel to the lowest point of land it can possibly get to. This is why water flows downhill. This feature of liquid water can create spectacular erosional features, especially if a stream finds itself having to cover more vertical distance than it previously had to. When a stream finds itself in such a situation, it begins to incise (which is eroding downward in a narrow fashion). Stream incision has led to formations like the Grand Canyon in Arizona, or the New River Gorge in West Virginia. And in western New York, stream incision led to the creation of Watkins Glen Gorge.
|Glen Creek as it begins cutting into the top portion of the Genesee Group layers.|
Glen Creek began incising deeply into the shales of the Genesee Group. The joints made it easier for the water to do so, as well. As we mentioned earlier, joints are an area in a rock layer that can be more easily eroded than a solid piece of rock. Essentially, joints allow for water to access and impact a greater surface area of the bedrock than a solid block of rock would allow. Liquid water in a joint can mechanically and chemically weather and erode the rock, and water in the joint can freeze and further crack and break apart the rock as the water expands.
For the past 12,000 years, Glen Creek has been carving its way down through the black shale and siltstones of the Genesee Group, exploiting the hundreds of joints found throughout the bedrock layer. A gorge dotted with waterfalls, plunge pools, and other features has since taken shape. This is Watkins Glen Gorge as we currently know it.
A Journey Through the Watkins Glen Gorge