u-NY-que New York: the Finger Lakes Part 1

by Timothy McDonnell, Coordinator of the New York Geographic Alliance

   In December 2019, I was asked by Erin McCormack of WXXI TV (PBS) in Rochester to sit down for an interview about the geography of the Finger Lakes Region. They are producing a program about the Finger Lakes, which will air most likely in May 2020. They wanted my “expertise” on many topics – geology, culture, history of the region, i.e. geography. While preparing for my on-camera moment, I had to consider why this region of New York is so special. You could say it is definitely “u-NY-que!”

   The centerpiece of this part of Central New York is the lakes themselves. As seen from space, they are definitely “finger-like,” all pointing in a roughly north-south direction. There are actually eleven Finger Lakes. They are, from west to east:-  2. Conesus, 3. Hemlock, 4. Canadice, 5. Honeoye, 6. Canandaigua, 7. Keuka, 8. Seneca, 9. Cayuga, 10. Owasco, 11. Skaneateles, and 12. Otisco. The Genesee River at Letchwoth State Park is #1. See the Google Earth image below. (Some locals argue that Silver and Onondaga Lakes should be included on the list, but the former is on the “wrong side of the Genesee River, and the latter is too far north.) The region also includes the land around the lakes, stretching from Lake Ontario (a “Great” Lake) to New York’s Southern Tier, just north of the Pennsylvania line. The common theme is the glacially-modified landscape of the region. If you look carefully at the image below, you will see many troughs. Some do not have lakes. 

   First we need to start with rocks. During the middle Paleozoic Era (450 – 370 MYA) of geologic time, most of New York State was under water in a tropical shallow sea. Erosion of mountains in New England formed large deltas in this sea, gradually laying down layers of mud, sand, and reefs. Over time they were transformed into sedimentary rock. These horizontal layers of rock are often rich in fossils: brachiopods, corals, trilobites, early fish, and New York’s official state fossil, eurypterids. (Sorry, no dinosaurs here. They came later in geologic history). After Pangaea, the Supercontinent, came together, New York was raised above sea level. For millions of years, the land eroded. A series of streams flowing north and south were established. Then, around two million years ago, the great Ice Ages began.

   With a cold climate during a period of time known as the Pleistocene, glaciers formed and spread out from Canada. They covered most of the northern part of the United States. Then, as temperatures warmed, they melted back, only to return again. The last glacial period reached its climax around 25,000 years ago. All of New York was under ice over a mile thick (except for a small area now in Allegany State Park). When the climate warmed again, the ice gradually receded northward until the only large glacier remaining was in Greenland.  Although the glaciers are gone, their impact on the region is profound. Incidentally, the Ice Age is not over; we are living in an interglacial period, which will end in a few thousand years.

   The immense pressure from the glaciers scoured the landscape. They left behind a gentle rounded topography, with one exception. The river valleys aligned with the movement of the ice was deepened and flattened. They are shaped like the letter “U” and are known as glacial troughs. There are about 30 such troughs throughout New York, and eleven of them have water-filled basins – the Finger Lakes. Although the lakes are narrow, they are deep. Cayuga and Seneca have bottoms below sea level.


    For lakes to become permanent, there needs to be a dam. The glaciers are responsible for that too. Around 14,000 years ago, as they were retreating, they paused just south of the lakes. The glaciers carried rocks and dirt of all sizes and they dumped them here, producing a wall of debris called the Valley Heads Moraine. This barrier prevented an escape route to the south into the Susquehanna Watershed, and ALL the Finger Lakes today flow to the north. The four western lakes empty into the Genesee River and the other seven flow into the Seneca River and then the Oswego River. All the water eventually reaches Lake Ontario.  Of course, this means that the Finger Lakes are part of the Great Lakes Watershed.



Photos above: Lucifer Falls in Robert Treman State Park, a hanging valley; the Valley Heads Moraine near Naples, NY; trilobite fossils at the Museum of the Earth in Ithaca, NY; a drumlin in Farmington, NY (a hill of glacial material molded into an oval shape)

   Another classic feature of the Finger Lakes are the waterfalls and glens. The highest waterfall in the Northeast is Taughannock, north of Ithaca, around 215 feet high. (Yes, Niagara Falls is in second place). The glens contain series of smaller waterfalls and rapids. But why are there here? The troughs have steep sides, so any tributaries coming from the west or east must tumble down the cliffs. They are hanging valleys. Watkins Glen is the most famous example, but similar features are found throughout the region. Ithaca, for example, at the foot of Cayuga Lake, is surrounding by these glens. “Ithaca is Gorge-ous!”

 Shortly after the ice left the region, Native People settled here. This became home to the Seneca, Cayuga, and Onondaga Nations, part of the Haudenosaunee (a.k.a. Iroquois) Confederacy. When Europeans arrived, the region was the frontier, fought over by the British and the French, and later by the rebel Americans. The human geography of the Finger Lakes is as interesting as the physical landscape: Erie Canal and the lateral canals, the Underground Railroad, Women's Rights, and making a living in the Finger Lakes.They will be topics of Part II of this series of u-NY-que New York. It will be online in early 2020.


Photo on the right: NYGA Coordinator, Timothy McDonnell, during his interview with WXXI television on December 13, 2019.