Ancient Lake Nipissing EarthCache
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This shoreline spot and the area all the way to the mouth of the Oconto River several miles downstream were completely submerged under the water of an ancient glacial lake 4,000 - 6,000 years ago. About 10,000 years ago, a global warming trend caused the Laurentide Ice Sheet to slowly melt and recede leaving behind several huge basins that would fill with the melting glacial water. These were to become the Great Lakes that we know today. With the weight of the ice sheet removed, a process called “isostatic rebound,” or uplifting of the crust, began. Because the rate of crustal rebound was different for different regions, various outlets opened and closed over the many years it took for the glaciers to retreat changing the sizes and shapes of the lakes. Beginning around 7 thousand years ago, these changes caused Lakes Superior, Michigan and Huron to become one huge body of water referred to as Lake Nipissing. Nipissing beaches at one time reached elevations of 629 to 635 feet above sea level. This large glacial lake had the unusual quality of having three outlets through the Ottawa-St. Lawrence Rivers, the Detroit-St. Clair Rivers, and the Illinois-Mississippi Rivers. Lake Huron continued to drain eastward out the Ottawa-St. Lawrence Rivers until about 5,000-6,000 years ago. Lake Michigan continued to drain out through the Illinois River where Chicago now stands until about only 3,000 years ago when the Great Lakes finally assumed their present shapes. Now, the major outlet is the St. Lawrence River. This rebounding effect is still occurring today. The Lake Michigan levels rebound about 30-50 cm. per century while Lake Superior averages about 53 cm.
Using your gps unit, mark the elevation here at the posted coordinates and, using the information above, determine how deep underwater it was during the high water stage of Lake Nipissing. Also, as you return on the trail to the parking area, notice the stone marker with engraving on the face (see Additional Coordinates). Don't confuse the stone marker with the interpretive sign behind it. It is located at the beginning of a high ridge that was the remnant of a Nipissing beach. The ridge of sand and gravel, referred to locally as Suzy’s Hill, was mostly excavated during the 20th century for road/street making. But during the Lake Nipissing era, a nomadic tribe of hunters/gatherers journeyed along its shores searching not only for food but for a particular metal left behind by the glaciers that they learned to fashion into tools. An archeological dig here in 1952 unearthed remnants and artifacts of this culture that were radio-carbon dated to 5556 BCE. From the engraving on the rock marker, you should be able to determine what this much sought after metal was as well as another unusual use they found for this high ridge of Nipissing beach.
E-mail me these three things to claim this earthcache:
1)The depth of the water at the posted coordinates at the time of the high water level of ancient Lake Nipissing,
2)the metal sought along this Lake Nipissing shoreline by the ancient nomadic people during post-glacial times, and
3) the unusual use of this Lake Nipissing beach by this ancient culture.
Do not list these three answers in your log or it will be deleted. Clicking on my name at the top of this cache page will allow you access to my profile page where my e-mail link is found. E-mail me the name of the cache and your answers.
The Geocache Notification Form has been submitted to the Wisconsin DNR. Geocaches placed on Wisconsin DNR managed lands require permission by means of a notification form. The DNR Notification form and land manager information can be obtained at: http://www.wi-geocaching.com/hiding. This form has been filed with Maggie Kailhofer, DNR Park Manager on 4/4/14.
Additional Hints
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