You are standing in front of a sign that marks a point on the SubContinental Divide, right there on busy 85th Street. Be sure to step out of the street and bike lane - stay safe. You can get the needed information quickly, but be sure to park someplace safe.
Wisconsin's Continental Divide
Where It Is
When we think of the "Continental Divide" we learned about in school, we usually picture the Rocky Mountains, or maybe the Appalachian Mountains. But the Continent itself has several drainage basins. Rain falling at various places in the U.S. could end up in the Atlantic or Pacific Oceans, Or the Gulf of Mexico, or even the Arctic Ocean. Some of it even ends up in Hudson Bay or the Gulf of St. Lawrence. And there's even one spot - the Great Basin, mostly in Nevada - where it doesn't flow to any ocean, but stays inland.
North American Continental Divides
Image from WikiCommons, attribution: By Pfly - Own work, CC BY-SA 3.0 - 12131177
You'll notice that in Wisconsin, a continental divide runs very near the Lake Michigan shore from Chicago to Milwaukee areas before heading more inland in the middle of Wisconsin. Much of this contour was created by the huge glacier ice sheets that originally formed the Great Lakes Basin. Many other Earthcaches in Wisconsin can offer information about that Ice Age geology. Be sure to visit some.
Great Lakes Basin
Image from Water Quality Report, U.S. - Canada Government
The eastern portion of Waukesha County has a major sub-continental divide as shown by the red line in the map below. Water falling west of this crest of land goes into the Fox River watershed and eventually into the Gulf of Mexico via the Mississippi River. Water falling on the east side goes into the Menomonee River watershed and enters the St. Lawrence Seaway by flowing through the Great Lakes.
Divide in SE Wisconsin - Kenosha-Pleasant Prairie
Image from SEWRP water report
Wisconsin's Continental Divide
What It Is
The Subcontinental Divide is an altitudinal (or land elevation) divide in southeastern Wisconsin running north to south along the Waukesha County/Milwaukee County border. It is a watershed between two drainage basins. Water falling to the east of the divide flows to the east towards Lake Michigan and eventually out the St. Lawrence Seaway into the Atlantic Ocean; water falling to the west of the divide flows west towards the Mississippi River, eventually flowing into the Gulf of Mexico.
Drainage Divide
Image from WikiCommons, modified by cache owner
This means you should be standing at a high point, so rain falling on one side of you runs into Lake Michigan, and rain falling on the other side of you runs into the Mississippi River. Look around you - can you see a slope? Can you tell which way water will run from where you are standing? It's all about the elevation of the land - where are the high points, because water flows downhill.
Notes on Water Levels
Great Lakes: The Great Lakes Basin is like a bowl - sometimes more water flows in than out, and sometimes water leaves faster than it flows in. In the big picture, it is all eventually draining out to the St. Lawrence Seaway and out into the Atlantic Ocean. The AVERAGE elevation of Lake Michigan is given as 577 feet. However, it has a recorded low of 576 and a record high of 582 feet. The current level is listed as 580.5 feet elevation. (source: NOAA Lake Michigan viewer, https://coast.noaa.gov/llv/#/lake/michigan) Mississippi River: The Mississippi River at Dubuque, straight west of Kenosha, has an average listed elevation of 585.5 feet. However river systems can flood and drain much faster than lakes and oceans, so the water level on the Mississippi River flutuates greatly over a short time. NOAA has a monitorig station at http://water.weather.gov/ahps2/hydrograph.php?wfo=dvn&gage=DBQI4
The Questions: You must answer - use your brain!
Send your answers to the following questions to the Cache Owner, either in message or email - see the top of the page under the title for the links.
- 1.) In what direction from the Continental Divide Sign is it toward Lake Michigan? North-South-East-West?
- 2.) How far away from Lake Michigan are you? (You could use your GPS or a map to estimate this.)
- 3.) In what direction from the Continental Divide Sign is it toward the Mississippi River? North-South-East-West?
- 4.) How far away from the Mississippi River are you? (You could use your GPS or a map to estimate this.)
- 5.) Can you tell my just looking that you are standing on a high point? What observations can you make to see if this is so?
- 6.) If you spill a bottle of water along the curb will you expect to see the exact high point of the Continental Divide? Yes or no, and especially WHY?
- 7.) Given that the current surface elevation of Lake Michigan is listed at 580.5 feet -
a.) How far downhill does water flow going from GZ to the Lake? (Use the elevation listed on the sign.)
b.) Since sea level is an elevation of 0 feet, how far does water from Lake Michigan drop on its way to the Atlantic Ocean?
- 8.) Given that the listed elevation of the Mississippi River at Dubuque is given as 585.5 feet -
a.) How far downhill does water flow going from GZ to the Mississippi River? (Use the elevation listed on the sign.)
b.) Since sea level is an elevation of 0 feet, how far does water from Dubuque's Mississippi River drop on its way to the Gulf of Mexico?
As always, a PHOTO of you at the sign is appreciated but not required. Thank you for visiting this Earthcache. I hope you have found it a learning experience, and enjoyed the information about the Earth and it's geology.