This is an Earthcache, which does not have a container, but rather brings you to a significant geological feature. Click
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A Bicycle Tour of Glacial Lake Middleton
This Earthcache will lead you to four stops highlighting several of the more significant features of Glacial Lake Middleton. The basic tour will cover approximately three miles (two optional stops may be added to the tour, lengthening the tour to close to ten miles). I highly recommend using Middleton’s excellent system of bike trails to complete the basic tour. However, if you wish to use your car, you may drive to areas near stops two and three. Stop four must be visited in person. All stops are wheelchair accessible, but note that the paved bike trail near stop four has a prolonged incline.
Glacial Lake Middleton
Stage One: The maximum advance of the Green Bay Lobe of the Wisconsin glaciation lays just a few miles west of Middleton (Optional stop A is at the point where HWY 14 crosses the line of maximum advance). During this stage, the glacier covers all the area of what will become Lake Middleton as well as Lakes Mendota, Monona, and Wingra.
Stage Two: As the glacier melts, a series of meltwater lakes are formed at the glacier’s edge. Lake Middleton is one of these lakes. The area covered by modern lakes Mendota and Monona as well as the isthmus between these lakes, remain underneath the retreating glacier which blocks the southern outlet to Lake Middleton. Thus water from Lake Middleton is forced to drain to the west into Black Earth Creek. As the glacier continues to melt, Lake Mendota begins to emerge. Because the southern outlet is blocked, water from emerging Lake Mendota flows west along Pheasant Branch Creek into Lake Middleton.
Stage Three: As the glacier continues to retreat, an outlet is opened over the isthmus. The first outlet is near Madison’s West High School (Optional Stop B). Since there is no evidence of a channel at this point, geologists believe this area formed a strait between Lake Mendota and early Lake Monona-Wingra which were at the same level. At this point water begins to flow south out of Lake Mendota. As the glacier continues to retreat, outlets are open at lower elevations dropping the level of Lake Mendota resulting in an increasing difference between the levels of Lake Middleton and Lake Mendota. Water now reverses direction in Pheasant Branch Creek and flows from Lake Middleton into Lake Mendota.
Post-glacial Lake Middleton
Sediment deposited at the bottom of Lake Middleton suggests the lake continued for a significant length of time following the final retreat of the glacier. However, by the time the first white settlers arrived in the area, Lake Middleton is no longer a lake, but marshland. This marshland is in turn drained by the early settlers to create agricultural fields.
Logging Requirements
Travel to stops one to four answering the questions below. Send yours answers in an email to me with “Lake Middleton Earthcache” in the subject heading.
Tour
Stop One: The tour begins in the parking lot of Quisling Park. (1) At the posted coordinates look to the north and northeast. What facility do you see? How is this facility making use of glacial Lake Middleton?
From the posted coordinates either ride east on the North Fork Trail or drive on surface streets to Stop Two. As you proceed to Stop Two you will be traveling on the dry lake bed, along the western shore of the former Lake Middleton. At the junction of the North Fork Trail and the Hidden Oaks Trail, take the Hidden Oaks Trail a few yards to the west to the second stop.
Stop Two: This stop is at the approximate divide between the Black Earth Creek and Pheasant Branch Creek watersheds. During stage two, water would have flowed west from here into Black Earth Creek. Look around you. (2) Based on the amount of erosion in the immediate area do you think there was a large volume of water flowing to the west out of Lake Middleton. If you look to northwest and southwest do you come to a different conclusion? If you do, can you suggest an explanation? (If you visit Optional Stop A, compare Stop Two with the side drainages you pass as you drive east from Stop A. Also, if you are going to visit Optional Stop B and your GPSr is capable, record the elevation at this point).
Retrace your path along the Hidden Oaks Trails back to the North Fork Trail and continue to travel east. At this point you will be leaving the western shore of the lake and crossing directly across the old lake bed. The southern shore of the lake is approximately where US HWY 14 runs today.
Stop Three: This stop marks the beginning of the Pheasant Branch ravine which has cut into the former lake bed. 3) Look to the west. What evidence of glacial Lake Middleton do you see?
Stop Four: This stop is in the ravine carved by the Pheasant Branch Creek. (4) At what stage do you think this ravine would have been carved? (5) What does the depth of the ravine suggest about the volume of water flowing here?
Optional Stop A: This "stop" is approximately where HWY 14 crosses the maximum advance of the Green Bay Lobe. (It is not necessary to actually stop at this waypoint as it is along a busy highway). As you drive east towards Middleton note the many significant ravines that lead into the valley you are in. Note also the change in elevation as you head east. (A) Is this change in elevation abrupt or gradual?
Optional Stop B: This stop is at the corner of Allen and Chadbourne in Madison. It is at this point that water would have been able to cross the isthmus for the first time as the glacier receded. If your GPSr is capable, record the elevation here. If your GPSr is not capable of recording elevations, look at the geocaching map for the area around Stop Two and Stop B and click on the MyTopo option and record the elevation for these two stops. (B1) What is the difference between the two elevations? The current lake levels are 849’ above sea level. (B2) What does the difference in elevation between the current lake levels and stop three contribute to your answer to question five?
References
Lee Clayton and John W. Attig, Pleistocene Geology of Dane County, Wisconsin. Wisconsin Geological and Natural History Survey, Bulletin 95. Madison: University of Wisconsin, Extension, 1997.
Robert H. Dott and John W. Attig, Roadside Geology of Wisconsin. Missoula, Montana: Missoula Press Publishing Company, 2004.
David M. Mickelson, Landscapes of Dane County, Wisconsin. Wisconsin Geological and Natural History Survey, Educational Series 43. Madison: University of Wisconsin, Extension, 2007.