Rocks for Jocks

I love rocks and I love Lake George. My dad started taking me to Lake George when I was 6 and it’s still the most beautiful place I’ve ever been. I can read about the formation of Lake George and picture the rocks I scrambled over on my way to the water. Lake George, as we know it today, has been around since the Pleistocene Epoch, only 12,000 years ago. To a geologist, that’s like yesterday; for non-geologists it was the most recent glacial period (the term “ice age” is incorrect, but when people think of the last ice age they think of the Pleistocene). The lake basin didn’t form until the Wisconsin Glacier retreated and dammed up the southern end of the lake with deposited sediment and erratics (a natural dam created by the retreat of a glacier is called a recessional moraine). Lake George is fed by 8 major streams and flows north, since the southern end is at a higher elevation. The north was clogged by a recessional morain as well, causing the formation of a lake instead of a river. Lake George enters Lake Champlain through the La Chute River in the town of Ticongeroga, which is where my summer camp is located. I’ve been to La Chute River many times but have never kayaked it (yet). The river is fast moving and has many falls and rapids, as it travels 230 feet in only 3.5 miles (it’s only a class II whitewater river if you don’t account for the falls).

I’ve always known Lake George as the second deepest lake in the Adirondacks, but I never knew why it reaches those depths. I did some more research after the reading about faults and it helped explain the depth of the lake. The southwest-northeast fault zones that exist all over the park exist around Lake George too. The Eastern shore follows a normal fault line (also known as an extensional fault) in which the Eastern side is the footwall and the lake bottom is the hanging wall. The mountains on the Eastern side either moved up a little bit or didn’t move at all, while the lake bottom slid down, creating a lake basin. On the western side of the lake, the same process occurred to create the basin, but there were multiple faults. The geologic terms for these features are graben and horst, which are German for trench and heap, respectively. I was excited to be able to connect basic structural geology to Lake George and it will be great this summer when I can point out geo to my campers, even if they get bored.

from the USGS

http://www.lakegeorgeassociation.org/what-we-do/Education/Lake-George-Basics/Lake-George-Formation.htm

https://www.americanwhitewater.org/content/River/detail/id/1335/