The Hanging Valleys of Door County
-
Difficulty:
-
-
Terrain:
-
Size: 
(other)
Please note Use of geocaching.com services is subject to the terms and conditions
in our disclaimer.
Ice Basics
An ice sheet is defined as a mass of ice that covers an area greater than 50,000 sq. km (20,000 sq. miles). An ice mass covering less than 50,000 sq. km is considered an ice cap. Ice caps typically feed even smaller ice formations called glaciers. Glaciers are then broken down into even smaller formations called lobes.
The Laurentide Ice Sheet
During its peak, the Laurentide Ice Sheet was almost two miles thick and covered over 13 million sq. km (5 million sq. miles). It most likely originated on the Labrador-Ungava plateau and on the arctic island mountains of Canada. Centered over Hudson Bay, it covered most of Canada, and a large portion of the northern United States. Its southern edge reached the modern cities of New York City and Chicago, and followed the present course of the Missouri and Ohio Rivers.
Wisconsin Glaciation
The most recent glacial advances and retreats in this area, were called the Wisconsin Glaciation Episode. It was subdivided into three separate and distinct periods, known as ice ages. These ice ages were, from oldest to youngest, the Tahoe, the Tenaya and the Tioga. The Tioga, the least severe of the 3, began around 30,000 years ago and came to an end around 10,000 years ago. The entire Wisconsin Glaciation began some 100,000 ago, and was the last major advance of continental glaciers to be born from the Laurentide Ice Sheet.
These Glacial Episodes contained within themselves the power to carve and erode the landscape as they slowly pushed their way southward. A larger, heavier ice mass would have greater potential to carve deeper into the underlying Strata, than a smaller, lighter ice mass would (generally speaking). As the ice flow gouged pieces from the landscape below, it would then engulf and transport these pieces within the ice flow itself. Upon melt-off and retreat (ablation), these fragments of Mother Earth were deposited far from their place of origin, creating Drumlins, Eskers, Moraines, Erratics and other geologic wonders.
Lobes
The advancing Wisconsin Glaciation Episode was channeled into the lowlands and impeded by the uplands of the Bayfield, Keweenaw, and Door Peninsulas. This created individual finger like projections, called lobes. During this period, six major lobes covered portions of Wisconsin. These were named, from west to east, the Superior, Chippewa, Wisconsin Valley, Langlade, Green Bay and Lake Michigan lobes, according to the area they occupied. As these individual lobes made their way toward the Southern end of the Great Lakes, they were reunited and continued southward as one broad sheet of ice (glacier). Not until melt-off and retreat did the ice sheet again become separated into distinct lobes.
In Northeast Wisconsin, the hard erosion resistant Dolostone of the Niagara Escarpment (Cuesta) served as a knife-edge, separating the southbound ice flow into 2 distinct entities, the Lake Michigan lobe and the Green Bay lobe. The Green Bay lobe carved a path in the soft Maquoketa Shale to the west of the Escarpment, forming what would eventually become the bay of Green Bay. The Lake Michigan Lobe was forced east of the escarpment, carving out the basin that would become Lake Michigan.
Four separate offshoots of the southwest flowing Green Bay lobe then flowed south southeastward across the escarpment, cutting valleys through the Cuesta. These valleys are: between the end of the peninsula and Washington Island, between Ellison Bay and Rowleys Bay, between Ephraim and Baileys Harbor and through the area that would become the city of Sturgeon Bay. The valley at Sturgeon Bay, which nearly cuts the Door Peninsula in two, is the most prominent and visible of the four. The 3 Northern valleys, having been filled by erosional deposits as much as several hundred feet thick, are now barely distinguishable from the surrounding landscapes.
Hanging Valleys
The junctions of main and side valleys are normally even, or accordant, in regions where there has never been ice flow. The junctions of main and side valleys created from ice flow, are almost always discordant, or uneven. The side valley lies above the main valley and is called a hanging valley. When a discordant valley lies below water level it is called a submerged hanging valley.
The depth of Green Bay where it ties into Lake Michigan is 100 to 144 feet. The depth of the straits to the north of Washington Island is approximately 156 feet. To the east lies Lake Michigan where the water depth averages 279 feet, with a maximum depth of 923 feet. Mid channel depth at this site is approximately 19 feet on average.
Inliers and Outliers
An Outlier is an area of younger rock completely surrounded by older rock. It is typically formed when erosion severs a section of rock from its original continuity with a larger mass of the same rock. An Inlier is just the opposite. It is an area of older rock surrounded by younger rock. The erosional effects of an ice flow can cause both Inliers and Outliers.
The given coordinates will bring you to the parking area. Just to the North of these coordinates is a waterfront walkway. Taking the walkway to the East (1,000 feet) will bring you to a scenic point, where the original railway bridge crossed the bay. The view from this point is spectacular and should be seen by all. Taking the walkway to the West (500 feet) will bring you to the actual site of the EarthCache (coordinates listed below). At the final coordinates you will find a small swing set that overlooks the bay. Have a seat on this set of swings, enjoy the view and answer the following questions. Email your answers to to me, using the link in my profile only. If your answers are not recieved by me, your log will be deleted. Photos are accepted and appreciated. You do not have to wait for confirmation from me before logging this cache as completed.
1. In your opinion, is the valley to the North deeper than the valley to the East of this position?
2. In your opinion, where would the erosional remnants of the valley to the East of you have been deposited?
3. 15 feet before you (to the North) lays a collection of various sized rocks and boulders. In your opinion, were these moved here by the effects of an ice flow or something else?
4. Look 3/10ths of a mile on a bearing of 351 degrees from this site. Would the "item" seen here, be considered an example of an Inlier, or an Outlier?
5. Which "specific" type of ice flow (ice sheet, ice cap, glacier, lobe or offshoot of a lobe) carved the valley to the East of the given coordinates?
This EarthCache was submitted to bring you to a scenic bayside viewing area and to help you better understand how the landscape before you was shaped and formed.
Additional Hints
(No hints available.)