Lake George Geological History
A shallow sea was in this area over the Proterozoic era (approximately 1.3 Billion Years ago). The sea formed sedimentary layers. Between 1.3 and 1.1 Billion Years ago, a mountain building process was started called an orogeny as a result of plates moving together. This area was called the "Grenville Orogeny."
From 550 Million Years ago through 450 Million Years ago this area was covered by the Iapetus Ocean. The Iapetus Ocean again deposited sediments, fossils, and precipitates. These sediments covered almost the entire area of New York
The Lake George geology was influenced and formed by faults. There is a fault running along the eastern shoreline of the lake where the bed of the lake slipped down on the west side of the fault. On the east side of the fault, the mountains remained at the same elevation or rose. On the western shoreline, the same process occurred.
A Graben is an elongated block of the earth's crust lying between two faults and displaced downward relative to the blocks on either side, as in a rift valley. The valleys of Lake George was created by stretching of the crust as this continent rifted apart (roughly 650 million years ago). The vertical displacement of Lake George was nearly 1500 feet.
Beginning 1.6 Million Years ago the climate began to cool and glaciers soon covered the northeast. Throughout the Pleistocene several ice sheets advanced over New York, each erasing evidence of the last. The last ice sheet was called the Wisconsinan ice sheet. As it crept over the surface, many surface features that we see today were formed. The glaciers bulldozed, scraped and crushed the surface soils and rocks, gouged out river valleys and carried materials forming a new landscape. As the glaciers retreated, deposits were left behind which allowed the Lake George basin to form. Some of the glacial features that are visible in New York include: glacial striations, eskers, drumlins, moraines, kettle lakes, and a lot of glacial till.
Lake George was formed as the glaciers receded about 10 to 12 thousand years ago. The ice sheet paused at the southern end of the lake just north of Glens Falls as it receded. This pause left behind a recessional moraine made up of boulders, stone, and sand forming a dam at the south end of the lake. A similar event occurred at the north end resulting in the basin that we currently see. The departing glacier left some ice behind to help fill the basin with water.
Lake George Today
Your Activities
1. Go to an area at the south end of the lake (the coordinates here take you to approximately the area of Million Dollar beach) and look at the lake and on the east and west sides of the lake. Send me an e-mail describing what you see in terms of evidence of the glaciers retreating
2. Go to the south end of the lake and describe what you see in terms of the recessional moraine
3. Using your best judgment estimate how wide the lake is on the south side of the lake