A Brief Geologic History of Lake Ontario

As a kayak fisherman, I tend to be pretty nosy about the areas I fish.  It’s one thing to know species, etymology, and structure, but I also like to know the history of the areas I fish as well.

A perfect Lake Ontario Paddling Day

In 2009, Lake Ontario drew my interest.  Fellow angler and exquisite fly tier Jude SanGregory brought me out to the Big Lake from the mouth of Maxwell Creek.  The topography of the New York shoreline of Lake Ontario is unreal and visually spectacular.  To me, watching the bald eagles soar over rocky bluffs makes me wonder about what it might have been like to fish here thousands of years ago.  Before the gobi, or the zebra mussel, or the man induced pollution that often closes the beaches in the Rochester area.

Recently, the History Channel series called How the Earth Was Made did a show on the formation of the Great Lakes.  Growing up in Buffalo, NY, and now living in Rochester, I’ve spent countless hours on the Niagara Escarpment… a geologic formation that surrounds 4 of the 5 Great Lakes, and which is chiefly responsible for Niagara Falls being the glory that it is.

Despite my ultimately dismal attempts to study geology in college, it had never really occurred to me what must have gone in to carving out the marvels that are the Great Lakes.  As it turns out, there were really only 3 mitigating factors chiefly responsible for their size and depth.  Rock, fire, and water.

Digging Out The Great Lakes – Lake Ontario

All 5 of our Great Lakes were ultimately dug by 6,500 foot thick ice flow that receded over 10,000 years ago.  The ice

The Niagara Escarpment

had covered 3 large rivers in the area, and chewed those river valleys wide and deep, forming the basins that eventually became the Lakes.  In between, all 5 were actually 1 lake, called Iroquois.  Since I wasn’t around to fish Iroquois 15,000 years ago, I’ll hold off on reviewing it.

Lake Ontario is the second deepest Great Lake, on average.  Reaching over 220 meters (700+ feet) in depth (also known as “several kayak lengths”), Lake Ontario is massive.  Only Lake Superior averages deeper.  In fact, it hits over 1300 feet in a basalt (volcanic rock) lined valley in a remote spot.

The other three are much shallower on average.  So why the difference?

According to the show, volcanoes are to blame.  Seismic activity in the depths of Superior and Ontario caused the substrate in their basins to be much softer, allowing the trillion ton glaciers to really get to work digging.  Note:  I couldn’t find anything on the web to back this assertion for Lake Ontario, but the similarity in the two Lakes make me think it’s good science.  And, here’s a map of recent (since 1991) seismic activity along the Escarpment and in Lake Ontario.

Shiver and Shake: Earthquakes on Lake Ontario

You may have been lucky enough to feel an earthquake in the last 20 years if you’ve lived here in Western new York that long.  The map below shows that there have actually been a LOT of recorded seismic events under Lake Ontario.  That lends a lot of credence to the assertion that there was a lot of volcanic activity in the region softening the substrate.

Most of these, however, appear to occur well west of Rochester.  Interestingly, looking at the Lake Ontario topography, the deepest spot is well EAST of Rochester.  Since I’m not a scientist, I can’t explain that for you.  I’m sure there’s a darn good reason however.  Like a good wife, geology can lie, but it rarely does.

The Earth is Righting Itself:  The Water is Heading Our Way

There’s a lot of talk about the depth of the Great Lakes recently.  Many reports indicate that the water is disappearing faster than Senko’s during a half price sale.  Scientists and fisherman blame everything from climate change to overuse of the resource for the Great Lakes’ water level dropping.

There is a very good, undeniable reason however.  It’s called “crustal rebound”.  Being under ice for as long as it was, the Earth’s crust was pushed down under tremendous pressure.  Over time, it is righting itself, rising back to it’s original configuration.  As it happens, water is being pushed south to the New York shoreline.

Eventually, the rebound will completely change the look of the Great Lakes region.  I’ll write more about the future of the Great Lakes region in future blog posts.

In Conclusion

I hope you found this discussion on one of my favorite places to fish interesting.  Like Wikipedia, by no means should you reference this in your Thesis.  In the end, it’s the musings of a kayak fisherman who draws a deep interest in the geology, entymology, and geography of the places he fishes in Western New York.

I hope to continue this series.  I’ve found it difficult to find information though on Western New York Creeks.   I will be digging though, and I will write them up as I find them.

Supporting and Dissenting Documentation

Here’s where I read a lot, and got some of the maps, for this article.  As with anything in science, some agree, some disagree.  In the end, it doesn’t affect the fishing.  But it’s fun to know.

http://www.ngdc.noaa.gov/mgg/greatlakes/lakeontario_cdrom/html/gmorph.htm#a

http://www.sentex.net/~tcc/gtlakes.html

http://www.erudit.org/revue/GPQ/1993/v47/n3/032963ar.pdf

Related posts:

1. Kayak Fishing For Trout and Salmon on Lake Ontario
2. Trout fishing in a kayak – Lake Ontario tributaries…
3. Ice-out (sort of…) on Conesus Lake, NY
4. Early Season Kayak Fly Fishing on Canadice Lake
5. Western New York Kayak Fishing Association, Loon Lake NY, 26 April 2009
6. Another failed bass fishing trip…
7. Early Bass Regs and Black Lake

Tagged as: fishing topo maps, Lake Ontario