Finger Lakes Geology: Cayuga Lake EarthCache

The Finger Lakes consist of 11 long, narrow, roughly parallel lakes, oriented north-south. They lie within an imaginary triangle between Syracuse, Rochester and Elmira-Corning. From west to east, the 11 Finger Lakes are Conesus, Hemlock, Canadice, Honeoye, Canandaigua, Keuka, Seneca, Cayuga, Owasco, Skaneateles, and Otisco. Two of the lakes (Seneca and Cayuga) are among the deepest in North America and have bottoms below sea level. These lakes all formed over the last two million years by glacial carving of old stream valleys.

Stewart Park in Ithaca is located at the south end of Cayuga Lake. Cayuga is the longest and the second deepest of the Finger Lakes at 38 miles long and 435 feet deep. The bottom of the lake is 53 feet below sea level at its deepest spot. The actual depth of carved rock is well over twice as deep, but it has been filled with sediments; there may be as much as 1000 feet of glacial sediment in the deep rock trough below the lakebed.

Finger Lakes Lore:

One look from above and it's easy to see why the Finger Lakes Region of upstate New York deserves its name. Each of the long, slender bodies of water forms a striking resemblance to the fingers of a hand. According to Iroquois legend, the lakes are the divine handprints of the Great Spirit. In blessing the land, the spirit's outstretched hands were placed over the region leaving each finger-shaped impression. The hollows that were left quickly filled with crystal-clear water forming the Finger Lakes.

Geologic Formation:

The Finger Lakes originated as a series of south-flowing rivers that existed in what is now central New York State. Around two million years ago the first of numerous continental glaciers advanced southward, initiating the Pleistocene glaciation, commonly known as the "Ice age."

The "Ice age" was really a series of many advances and retreats of glaciers. The latest glacial episode was most extensive around 21,000 years ago, when glaciers covered almost the entire state. Around 19,000 years ago, the climate warmed, and the glacier began to retreat, disappearing entirely from New York for the last time around 11,000 years ago.

The Finger Lakes were carved by several of these episodes of glacial scouring. Ice sheets more than two miles thick flowed southward, gouging deep trenches into these river valleys. Whereas streams only erode as far down as sea level, glaciers are able to erode more deeply. The bottoms of two of the Finger Lakes (Lakes Seneca and Cayuga) are actually below sea level.

In additon, as the glaciers advanced, they pushed great quantities of soil and rock ahead of them, like giant, slow-moving conveyor belts. When the ice sheets began to melt and retreat, they left these vast deposits of material behind. This glacial till material dammed the stream valleys at their southern end. The valleys then flooded to form the Finger Lakes.

Accumulations of glacial debris are called moraines, and the piles left at the end (or snout) of a glacier are called terminal moraines. Before the most recent ice age, many streams of the Inland Basin region (especially in New York and Pennsylvania) flowed south into the Susquehanna River. However, the Valley Heads Moraine, blocked the flow of water to the south, damming the Finger Lakes and forcing streams to drain north into the St. Lawrence River Valley

To Log this Earthcache you need to complete the following task:

• Take a photo of yourself with your GPS at the posted coordinates with the lake in the background.
• In your log, post your photo.
• Send me an e-mail with the answer to the following questions:
  (1) What is unique about the depth of Cayuga Lake and what made that depth possible?
  (2) What direction does the water in the lake flow, and why?