A Rivers Course
The original path of the Genesee river is thought to be that of Irondequoit Creek and the Bay it's mouth. Here at this location you can see evidence of a great river that carved out the landscape. Topographical maps show a steep change in grade, and a wide, deep valley. This valley was not entirely made by Irondequoit Creek, but rather inherited from the Genesee river after the last ice age.
For thousands of years before the last ice age, an ancient Genesee river flowed through our landscape. The river carved out a wide river valley as it twisted through the land on its journey to a northern lake. Then about twenty thousand years ago glaciers began to cover the land. The ice was so massive, at over a mile thick in some places, that it changed the landscape, but not entirely.
This wasn’t the first time that glaciers had scoured the land here. In some places they carved deeper into the finger lakes. The glaciers moved southward carrying stone and soil, following paths that had been impacted before.
Then the ice began to melt and leave behind all the stone and soil that the glaciers had scoured along their path. South of the glacial ice, the Genesee river was flowing northward from Pennsylvania.The preglacial course of the river had now been blocked by the ice dumping huge amounts of glacial till in the form of moraines, along the rivers eastward path. With this path blocked, the river found another way north to Lake Ontario, cutting a new channel and creating three waterfalls where it crossed the Niagara Escarpment, in what is now Rochester NY.
The ice from the glaciers continued to melt and the Genesee river continued to carve its new course. The old river valley was being flooded by the lake and over time filled with glacial till and lake sediments. When the glaciers finally receded and the lake was able to drain out through the Saint Lawrence sea way, new streams found this ancient river valley and cut into the soft sediments and glacial deposits. This created the course of the Irondequoit creek that we see today.
Standing here today we can see that this area was carved out by forces greater than the rather tame Irondequoit creek. We can also see how the creek has carved its way through the loose deposits left by the last glacial event. It has always amazed me as to how this deep valley came to be here and it’s surprising relation to the Genesee river that explains so much.
The old geohydrology survey map pictured below shows great topographical details of the irondequoit creek watershed and the shaded area shows where the Genesee river once flowed through this area. 
Quiz Time
After answering the questions below, click on the link at the top of the page that says "message owner". Paste the questions and your responses in a message to Fireside796 to receive credit for finding this cache. Alternatively you can send me an email, just be sure to include the name of the Earth cache in your response.
1. How far away from here is the Moraine field that blocked the flow of the Genesee river?
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2. Irondequoit creek has cut deep into this ancient river valley. Looking out across the creek, how high, in your estimation, are the cliffs at this location?
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3. What material are the cliffs primarily comprised of?
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- Was this material carved into by the Genesee river or deposited after the course change?
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4. It was the last ice age that brought about changes in this landscape. How many years ago did the glaciers begin to cover the land?
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Disclaimer:
I am in no way a geology expert. All the information I have obtained in creating the above description has been from studying topo maps, observations I have made in the area, information read on trail kiosks, and internet research. Take this information as you will.