Bluff Point & Keuka Lake Geology
The Seabed Became A Plateau
The Keuka Lake region belongs to a topographic province called the Allegheny Plateau. The shale and sandstone formations found here represent mud and sand deposits that settled on a shallow sea floor over millions of years. These sediments gradually became rock under the pressure of successive layers in a process called lithification. Many area gorges and glens contain fossils such as trilobites, brachiopods, and corals. Geologically speaking, the surface rocks belong to the West River Group and are sandstones, siltstones, and shales originating from the erosion of the Acadian Mountains to the east. These mountains were a product of the collision of the North American and Avalonian Plates. The region first became dry land more than 300 million years ago during late Devonian times. A long period of uplift and erosion began. During this time, about one vertical mile of rock material was eroded from the original two-mile-thick stack by a system of rivers that developed in the area. One such river occupied the Keuka valley.
Glaciers Covered The Area
The Ice Age or
The continental ice sheets slowly flowed into existing river valleys as valley glaciers, massively reshaping the topography. The valleys running north-south were greatly deepened and changed from a V-shaped cross-section to a U-shaped one by the south-flowing ice. As the advancing ice sheet thickened, ridges between the glacially deepened valleys were sculpted by the flowing ice into steamlined forms as seen in the ridges between the east and west branches of Keuka Lake. The last continental glacier was at least one mile thick.
The Bluff Was An Island
As the last glacier slowly melted and retreated northward, it stalled about 17,000 years ago for a period of time and dumped what has been called the Valley Heads Moraine. This formed a barrier preventing southward drainage of glacial meltwaters. A part of this barrier remains today as the hilly topography between Hammondsport and Bath.
Around 15,000 years ago the water level in the Keuka valley
The Finger Lake That Is A "Y"
When underlying shale layers were eroded, harder sandstone on the Bluff's crest resisted. As ancient rivers flowed around the Bluff, it remained, creating today's "Y" shape. Major inlets to Keuka Lake are located at Hammondsport and Branchport. The outlet is in Penn Yan, where the lake level is regulated by a set of gates. From this outlet, water drains to Seneca Lake and then northward through the Seneca-Oswego-Oneida Rivers Drainage Basin, eventually reaching the Atlantic Ocean via Lake Ontario and the St. Lawrence River.
The highest points in the Town of Jerusalem are on the Bluff and the Pinnacle (the hill behind you), each about 1,400 feet above sea level. There are spectacular views from Esperanza Road and along Skyline Drive.
[Illustration captions, clockwise from top center, read]
Glaciers followed existing streambeds leaving Keuka as
The east, west, and south branches of Keuka Lake embrace the Bluff.
The force of water and glaciers contributed to the formation of gullies and glens found around Keuka Lake.
Keuka Lake Watershed [bottom left, and] Finger Lakes Watershed [immediately adjacent to right]
Erected by Bluff Point Association.
Topics. This historical marker is listed in this topic list: Natural Features.
Location. 42° 35.693′ N, 77° 8.228′ W. Marker is near Branchport, New York, in Yates County. Marker is on New York State Route 54 west of Esperanza Road, on the right when traveling east. Marker is at the roadside pullout. Touch for map. Marker is in this post office area: Branchport NY 14418, United States of America. Touch for directions.
Other nearby markers. At least 8 other markers are within walking distance of this marker. Bluff Point & Keuka Lake History (here, next to this marker); Beddoe Tract (within shouting distance of this marker); Bedford-Rose Cemetery (approx. half a mile away); "Ahweyneyoun" (Ah-Wey-Ne-Youn) (approx. Ύ mile away); Veterans Memorial (approx. Ύ mile away); Trolley Depot
Credits. This page was last revised on August 3, 2020. It was originally submitted on August 3, 2020, by William Fischer, Jr. of Scranton, Pennsylvania. This page has been viewed 273 times since then and 4 times this year. Photos: 1, 2, 3. submitted on August 3, 2020, by William Fischer, Jr. of Scranton, Pennsylvania.