"It's a dangerous business, Frodo, going out of your door" … "You step into the Road, and if you don't keep your feet, there is no knowing where you might be swept off to."
~ Bilbo Baggins from The Fellowship of the Ring by JRR Tolkein

Saturday, May 9, 2015

The Lake Michigan water basin and why it matters for North Shore cyclists

I find it interesting that in Northern Illinois the Lake Michigan watershed ends just two blocks to the west of my house, on Ridge Rd. up by the grocery story.  We're so close to The Lake, yet all the water to the west of us flows to the Mississippi, even that in our storm sewers. Then too, the water that does flow into The Lake takes almost 100 years to empty out through the Straits of Mackinac.

Old shorelines make for interesting weather

If you make a study of it you'll learn that Lake Michigan was in fact much larger thousands of years ago. Shrinking to current levels, it left a series of old shorelines, now ridges in its wake. Where we live the land between these ridges is so flat and close to the water level it is naturally swampy. Native Americans used these old ridges to stay above the swamps while traveling along the lake. European settlers drained the swamps and turned the ridges into wagon trails, then roads and now expressways. 

The ridges also form natural weather breaks, trapping the cool breezes from the lake close to the shore, moderating the high and low temperatures. Our spring and summer weather is cooler as The Lake is warming up, our fall particularly nice for the opposite reason. In winter, to add to our already infamous cold, those of us close to the water can get something unique to the Great Lakes - lake effect snow. That unpredictable, localized, wet and usually DEEP stuff comes pouring off the lake, burying us in six, ten or even twenty inches.  Buffalo, NY suffers from the same effect only more so. 

When we ride our bikes to the west, we cross many of these ridges (several actually called Ridge Road - very confusing for a newcomer). Each time we cross one the weather gets warmer and often a little less humid. Around here we have a very famous (infamous?) saying "Cooler Near the Lake." That's great in the summer when in-land its 90s, but 70s at home. Not so nice in the early spring when its 60s in-land and still 40s around here. When riding from west to east we frequently cross a very definitive line, the Edens Expressway, Sheridan Road, or Ridge Road (in its various forms) where the temperature instantly drops 10Âș or more. A smart cyclist comes prepared for just such an event with an extra pair of socks. 

Some Glacial History

Instructive sign in Kenosha next to the 1936 Southport Bath House

While passing through Kenosha during our trial run, Will and I found the above sign posted right next to the Kenosha (Southport) bath house I mentioned in an earlier post. (If you click on the photo you can get an enlargement.) The graphic shows the impact the most recent glacier had on the Great Lakes from 14,000 years ago to almost the present. Those of us in the Chicago area can see the irony that even before the 20th century engineers set about reversing the flow of the Chicago river, from north to south,  that's the direction it flowed naturally up until about 9,000 years ago. They had a BIG job doing it, but the close proximity of our local Continental Divide made the whole thing possible. You can also see from the last panel,  the water basin is wider than the lakes by a significant amount in all directions EXCEPT for here in northern Illinois. This geological fact played a very important role in why Chicago came to be the fastest growing US city in the 19th century. Stay tuned for more on water routes and they're  exploration / exploitation by European settlers starting in the 1600s.

For now, click on the link below you'll see that for the small little area, encompassed by my zip code, there are not just two, but THREE watersheds, meaning three ways the water can flow. No wonder it tends to pool, swamp like - can't make up its mind I guess.

You can also check out some interesting statistics by clicking on the page labeled "Lake Michigan Statistics" in the right column.

No comments:

Post a Comment