National Scenic Trails - Ice Age Trail Overview
At the end of the Ice Age, about 10,000 years ago, glaciers retreated from North America and left behind a chain of hills that defined their southern edge. In Wisconsin, this band of hills zigzags across the state for nearly 1,200 miles, from Lake Michigan to the Saint Croix River. A trail along these hills was conceived by Ray Zillmer in the 1950s and publicized by Rep. Henry Reuss in his book, On the Trail of the Ice Age. Today, with help from the state of Wisconsin and the Ice Age Park and Trail Foundation, almost half of the trail is open to public use. Certain sections are popular for marathons, ski races, and ultra-running.
When the ice melted at the edges of the lobes, the sand, silt, cobbles, and boulders frozen in it were released and formed ridges called moraines. Even as the glacier melted back, ice usually continued to flow toward its edge, bringing more debris with it. Occasionally the flow stopped, the ice stagnated, and blocks of ice detached from the glacier were buried in debris. Many of Wisconsin's lakes lie in the depressions formed by the melting of the buried ice.
The moraines vary greatly across the state. Those in the southwest are usually dry, narrow ridges sitting atop the older hills at the edge of the un-glaciated Driftless Area. Across the northern counties, the moraines form a broad band of hills dotted with lakes, marshes, and bogs. The Chippewa Moraine Ice Age Reserve Unit is a particularly picturesque portion of these moraines, containing numerous depressions filled with lakes, bogs, and marshes. The moraine in Waushara County in the center of the state is similarly pitted with thousands of these depressions, but most often are dry. The rugged, scenic Kettle Moraine in the eastern part of the state is actually a series of moraines formed between Lake Michigan and the Green Bay Lobes. The Green Bay Lobe also left a moraine in Sauk County, which blocked both ends of a gorge in the Baraboo Hills, creating Devils Lake. Some moraines stand no more than 30 feet above the surrounding terrain, but others in the Kettle Moraine rise to heights of 250 to 300 feet.
Streams flowing over, under, and beyond the glacier also left deposits that vary our landscape. The conical hills of water-rounded sand and cobbles called kames, which stud parts of the Kettle Moraine, are deposits of streams that flowed downward through cracks in the ice. The sinuous eskers, such as the one near the Mondeaux Flowage Taylor County and the Pamell Esker in Sheboygan County, are ridges of rounded sand and gravel at the base of the glacier. Like drumlins, they are usually aligned parallel to the ice flow.
The flowing melt water spread fine layers of sand in broad plains, such as those in Langlade, Rock, and Portage Counties, which today are fertile cash crop farming areas. In several areas the melt water pooled, forming large lakes where silt and clay collected. The flat bed of glacial Lake Wisconsin, one of these lakes, is a marked contrast to the un-glaciated hills of the Driftless Area that bound its western side. In the Fox River Valley, Lake Winnebago and Horicon Marsh are small remnants of another pro-glacial Lake Oshkosh.
The torrents of melt water released from the wasting glacier or draining glacial lakes cut spectacular gorges in several areas of the state. Some, such as the Dalles of the St. Croix, the Wisconsin Dells, and the Dells of the Eau Claire, are still occupied by streams. Others, like the smaller gorge at the Cross Plains Ice Age Reserve Unit, are now dry save spring and storm runoff.
Although many of these features are outstanding by themselves, seen as a whole they form a glacial landscape of remarkable beauty. The thousands of drumlins, kames, and kettles and the numerous moraines, eskers, and other features left by the fluctuating lobes of the last Wisconsin glacier appear very similar to features being formed by today's active glaciers. The region of recent glaciation is dotted with over 14,000 glacial lakes; numerous bogs, marshes, and fens; and many streams whose courses are determined by the young glacial deposits. In a sense, this region of the state is still recovering from the melting of the last glacier. As the streams slowly wash away kames, eskers, and moraines, and as marshes, bogs, and lakes fill with sediment and organic debris, this young landscape will become like the older glacial landscape that lies between the Driftless Area and the terminal moraines of the most recent glaciation.
Details mentioned in this article were accurate at the time of publication