Drift

 Drift can apply to a number of items.  My spouse says when I drive the car will drift, or veer, to the side when I decide to look out a side window.  Soil can drift, the loess plains of the United States is evidence of this fact. Those who live in the north are most familiar with snow drifts which can reach several feet high.  But, drift also refers to the glaciers, and notably Wisconsin is unique among the northern tier of states as it contains what is known as the driftless area, an area not subject to glaciation. This past Tuesday my wife was fortunate to experience at least two of the above noted drifts: my drifting while driving (although with lane deviation assist is more tame (otherwise the wife app would have been in overtime mode) and experiencing part of the dirftless area of the State on a trip to Wyalusing State Park.

View of Wisconsin River from Wyalusing State Park
If one had stood here about 12,000 years ago
you would have seen "rolling bluish-grey floodwater"
coming through and scouring the valley

The driftless area composes much of the southwest quarter of the state.  Yet, it also reaches what we would call the northern part of the state as it reaches almost as far north as the Eau Claire area. Over historical time, during the ice age, four glaciers are thought to have covered much of Wisconsin.  But, the driftless area was not covered by any of the main four glaciers that came south of the Laurentian ice shield in Canda.  There is an area that was covered by one or more of the previous glaciers, but not the last glacier. The last glacier is known as the Wisconsin Glacier, or in parts of Europe as the Wurm Glaciation. The Wisconsin Glacier consisted of three main lobes: Lake Michigan to the east, Lake Superior (and its subsidiary lobes) to the north, and the Green Bay Lobe, between the two  The demarcation line between the unglaciated and glaciated landscapes in some cases is easy to determine, and in others not.  For example, even though the glacier did not reach the driftless area, that does not mean that area was not impacted by the glacier. Glaciers held significant amounts of water, stored as ice, and as they retreated the meltwater flowed out.  Besides leading to some really interesting geographical features, such as kames (Holy Hill is a kame, part of an interlobal moraine, that sits atop the Niagara Escarpment, providing its commanding view.) and eskers, it led to what is known as Glacial Lake Wisconsin and the vast region of sand country in the central part of the state. 

Sandstone at Wyalusing, Oct 2020 photo

Glaciers had large reaching effects along river or stream valleys.  Devil's Lake was created when the glacier reached its terminus and deposited debris, known as the terminal moraine, near blocking and re-routing river flow and creating Devil's Lake. Some say the Wisconsin River used to flow through this area, and it was re-routed by the deposition of the moraine material. The road entry to the north shore of Devil's Lake was covered with glacial ice, but the glacier did not affect the high uplands of the Devil's Lake area.  The bluffs of Devil's Lake are a monadnock, old mountain range that has eroded.  A terminal moraine plugged two ends of the river course creating what we know now as Devil's Lake.  

Map of Moraine in relation to Devil's Lake
Clayton et al, 1990

When I was much younger, as a pre-teen and a teenager, the old wives tale was that Devil's Lake was very very deep, some say it contained large turtle like sea monsters.  While popular with divers, the lake is about 35' deep.  My wife, in her pre-Tom life, scuba dived Devil's Lake. The large quartz and sedimentary rock bluffs sitting either side of the lake can easily give a false impression of remarkable depth, as the rocky bluffs and boulder fields rise out of the water. As an old river bed, it would not be expected to be overly deep.

Extent of Glacial Lake Wisconsin

The meltwater also affected areas far west in the state. For example, while the Prairie du Chien area is known as the former home of Campion Academy, and saw much in terms of teenage antics of Joseph R. Sweeney, it sits near the confluence of the Wisconsin River with the mighty Mississippi River.  Glacial meltwater was carried down the Wisconsin and Mississippi Rivers and in so doing deposited sand and gravel, part of its debris, as it scoured down the erosion carved valleys.  

Dolomite Cave at Wyalusing, Sept. 2017 photo

The neat thing about traveling west from Madison area to Prairie du Chien is the varied landscapes through which one travels, or in my case the car drifts side to side as I marvel and think about the geography and geology of the regions and the power of nature.  Just east of McFarland, I see drumlins, and we can view recessional moraines, cross the terminal moraine and head to the hill and valley area of the Coulee region.  Scattered throughout are mounds, such as Blue Mounds, which along with others  and others are capped by Silurian chert and/or dolomite.  These mounds punctuate the landscape of southwest Wisconsin.  High on a ridge as we travel on Hwy 18 to Prairie du Chien, the vast overlook of provided from the ridge allows one to view miles distant of contoured cropped farm fields with mixed hardwood woodlands that cover the steep slopes, too steep to properly farm.  

Sandstone Cave and Waterfall at Wyalusing, Oct 2020 Photo

As Hwy 18 approaches Prairie du Chien we travel a few miles on county roads to Wyalusing State Park.  This park provides vast and stunning views of the Mississippi and Wisconsin River valleys. These valleys were formed by erosion of water and wind, and accepted the glacial surcharge of water further scouring the valley. With Wyalusing being underlain by sandstone and limestone, there arise some highly interesting formations.  A sandstone cave next to a creek flow, but probably carved out by larger water flows now distant.  There also exist a limestone cave and the karst topography of sink holes created by water flow dissolving limestone or dolomite.  The running water dissolves calcium in the dolomite leaving crevices which then can lead to sinkholes.

Wisconsin Glaciation

Seldom do we take the time to understand the underlying nature of our landscapes.  We see the hills, and valleys, ridges and plains; we see rivers and lakes; but we really do not fully comprehend why and how that landscape came to be formed? The physical geography of the state influenced, and to this day still influences, settlement patterns and human activity.  The human landscape types that we see cannot be ignored, but to a large degree are formed by the landscape. The more we know about our natural and human landscape types perhaps the more appreciation we can have of their existence, and the value they provide to our heritage. As you travel across Wisconsin, you should come to appreciate the varied natural, or physical landscape types, and then examine how we humans have interacted with, and changed, the landscape. Perhaps you may drift, but be careful as you discern the landscapes in which we find ourselves.

Dolomite Outcropping, Wyalusing, Oct 2020 photo