The Earth is Constantly Changing
Soils and sands get washed from mountainsides and settle into lakes and oceans where they are naturally compressed into layers of sedimentary rocks. The layers of rock are like pages of a book and tell the story of how and when they were made.
During the last Ice Age, giant sheets of ice, or glaciers, formed and covered parts of the earth. As these glaciers slid over the earth's surface, they carried rocks, soil and sand, carving out valleys and leaving deposits that formed into hills and mountains. As the glacial ice melted, the receding water formed lakes, which were drained by new rivers, spreading sand and soil and carrying them back to the oceans to form new rock layers.
Before you is a magnificent view of the Genesee River Gorge. The gorge or bowl was carved by the flowing waters of the Genesee River from layers of bedrock beneath it. These layers of different rocks, including shales, date back to the late Ordonician Period some 430 million years ago. Waters of the river began carving deeply into the bedrock at the end of the last glacial periods, called the Wisconsonian Ice Age, over 20,000 years ago.
During the Ice Age, water from the melting ice caps formed into three glacial lakes - Lake Scottsville, Dawson and Iroquois - that covered much of New York State. Over 20,000 years, as water drained, the rivers that formed cut through the bedrock, creating waterfalls. The unique geology provided the immense water power that fueled Rochester's explosive growth.
The source of the Genesee River has been traced to Potter County, Pennsylvania. From there it flows northerly, about 155 miles into Lake Ontario. There was a time when the river flowed easterly to form Irondequoit Bay. Then glacial debris filled the river bed and eventually channeled the river to its present course. Honeoye and Irondequoit Creeks, in Southern Monroe County, follow the same course as the pre-glacial Genesee River to the mouth of Irondequoit Bay.
Looking at the sheer wall on your left, you can see the layers of shale from the Clinton Formation, which dates back over 400 million years to the Silurian Age, a time when sea life multiplied and animal life first appeared on land.
At the left edge of the falls, you can see brick remains of a plant that once supplied power to factories along the eastern bank. The man-made archway, cut into the rock, was once a storm sewer outlet.
When the glacial waters first carved out this gorge, the lip of High Falls was originally located almost one-half mile to the north. Even today, after millions of years, falling water continues to erode the bedrock, both at the falls and along the gorge walls. When Francis Brown fist saw High Falls it towered some 96 feet, but 20th century flood control measures reduced the height in order to accommodate a greater volume of water.
Today the lip of the falls is only about 80 feet above the pool at its base.
On the right side of High Falls is a wing wall, a man-made structure that forced water into channels cut into the bedrock under the Gorsline Building foundations. At the base of the falls, a tail race cut into the rock allowed the same water to turn the water wheels and return to the river.
All along the west side of the gorge on the right, you can see a series of tail races cut into the bedrock, marking where 19th century industries were located. You can also see, on the lower level, a small, light brick building, which is one of only three plants on the river that still produces hydroelectric power.New York State Heritage Areas - a program of NYS Parks.City of Rochester, NYBrown's Race/High Falls Historic District