(Redirected from Driftless Zone)
Relief map showing primarily the Minnesota part of the Driftless Area. The wide diagonal river is the
Upper Mississippi River. In this area, it forms the boundary between Minnesota and Wisconsin. The rivers entering the Mississippi are, from the bottom up, the
Upper Iowa,
Root and
Cannon Rivers. A small portion of the upper reaches of the
Turkey River are visible west of the the
Upper Iowa. To the west, outside the Driftless Area where more regular topography is evident, tributaries of the
Wapsipinicon and the
Cedar Rivers are seen.
The 'Driftless Area' or 'Paleozoic Plateau' is a region in the American
Midwest noted mainly for its deeply carved river valleys. While primarily in southwest
Wisconsin, it includes areas of southeast
Minnesota, northeast
Iowa and northwest
Illinois (see map at right). This region includes elevations ranging from 603 to 1,450 feet (184 to 442 m) and covers an area of 16,203 square miles (41,986 km²). This region's peculiar terrain is due to its having escaped
glaciation in the most recent
ice age.
[1][2]
The term "driftless" indicates a lack of glacial
drift, the material left behind by retreating continental glaciers.
Geological formation
The Driftless Area is a product of the last
ice age, but in contrast to
what happened in the regions to east, north and west, this area was spared the three phases of the
Wisconsinian glaciation.
"Retreating glaciers leave behind silt, clay, sand, gravel, and boulders — called
drift. Glacial drift includes
till (unsorted material) and
outwash (layers deposited by meltwater streams)".
[3] While some glacial drift has been discovered, this is said to be of "
pre-Illinoian-age"
which puts it in the period of the
Kansan glaciation, nearly a half million years ago.
[4][5]
What is clear is that the region has been subject to the regular catastrophic effects of
glacial lake outburst floods involving the
cataclysmic collapse of
ice dams holding in such bodies such as
Glacial Lake Agassiz,
Glacial Lake Grantsburg, and
Glacial Lake Duluth (''see''
Jökulhlaup).
The earlier local phases of the Wisconsinian glaciation are poorly understood, but the last involved several major lobes, the
Des Moines lobe, which V'd down to Iowa's capital city on the west, the
Superior lobe (and its sublobes) on the north and the
Green Bay lobe and
Lake Michigan lobes on the east.
[6] The northern and eastern lobes were in part diverted around the area by the
Wisconsin Dome, an exceedingly ancient uplifted area of Cambrian rock underlain by
basalt. The Green Bay and Lake Michigan lobes were also partially blocked by the bedrock of the
Door Peninsula, which presently separates
Green Bay from
Lake Michigan.
[7] In earlier phases of the Wisconsinian, the Driftless Area was totally surrounded by ice, with eastern and western lobes joining together to the south of it.
In the adjacent glaciated regions, the glacial retreat left behind drift which often totally buried all former topographical features, with surface water forced to carve out new streambeds.
[8]
Characteristic landforms
Geology
Overall, the region is characterized by an eroded-down
plateau with bedrock overlain by varying thicknesses of
loess. Most characteristically, the river valleys are deeply-dissected. The bluffs lining this reach of the Mississippi River currently climb to not quite 600 feet. In Minnesota, pre-Illinoian-age till was probably removed by natural means prior to the deposition of loess. The sedimentary rocks of the valley walls date to the
paleozoic and are often covered with
colluvium or loess.
[9]
Bedrock, where not directly exposed, is very near the surface and is composed of "primarily
Ordovician dolomite,
limestone, and
sandstone in Minnesota, with
Cambrian sandstone,
shale, and dolomite exposed along the valley walls of the Mississippi River."
In the east, the
Baraboo Range, an ancient, profoundly eroded
monadnock has some of the most ancient exposed rock in North America, primarily
quartzite and
rhyolite. The area has not undergone much seismic action, as all the visible layers of sedimentary rock are approximately horizontal.
Karst topography is found throughout the Driftless. This is characterized by
caves and cave systems,
disappearing streams,
blind valleys, underground streams,
sinkholes,
springs,
cold springs and cold streams. Disappearing streams are when surface waters sinks down into the earth through fractured bedrock, either joining an
aquifer, or becoming and underground stream. Blind valleys are formed by disappearing streams and lack an outlet to any other stream. Sinkholes are the result of the collapse of the roof of a cave, and surface water can flow directly into them. Disappearing streams can re-emerge as often powerful springs, often having been cooled down by the water's journey through the earth. Cold streams with cold springs as it sources are noted as superb trout habitat. All of these features are found in the Driftless area.
Rivers
As rivers and streams approach their confluence with the Mississippi, their canyons grow progressively steeper and deeper, particularly in the last 25 or so miles (40 km) in their journey to their mouths. The change in elevation above sea level from ridgetops lining a stream to its confluence with the Big River can reach well past 650 feet in only a few miles. The
Waukon Municipal Airport is reliably established as being 1281 feet (390.4 m) above sea level.
[10] The
Army Corps of Engineers maintains a river level in
Pool 9 of 620 feet above sea level,
[11] which covers
Lansing. Maps and signs issued by the
Iowa Department of Transportation indicate Waukon and Lansing are 17 miles apart on
Iowa Highway 9. This is a drop of 660 feet in less than 20 miles (and this along a
very minor tributary of the Mississippi). "The role of
isostatic rebound on the process of stream incision in the area is not clearly understood."
There are many small towns in the Driftless Area, especially in river valleys, at or upstream from the Mississippi. Small towns in a deep steep valley going down to the Mississippi are at risk every 50 to 100 years or so, as with the wreck of
Gays Mills, Wisconsin in August 2007, or the holding of the levee in
Houston, Minnesota (on the South Fork
Root River) at the same time. Metropolitan areas have flood walls.
The Driftless Area goes from
Pool 2 to
Pool 13.
The history of this portion of the Upper Mississippi actually dates back to an origin "as an ice-marginal stream during what had been referred to as the “
Nebraskan glaciation” (''see
Beestonian stage''). Current terminology would place this as Pre-Illinoian."
The level of erosion often exposes Cambrian limestone of about 510 million years of age.
[12]
The Mississippi River trench is an exception to the rule about shallow bedrock, and is overlain by large amounts of sediment.
[13] As home to the formation of a substantial portion of the gorge of the Upper Mississippi, this enormous quantity of sediment goes down at least 300 feet under the present riverbottom at the confluence of the
Wisconsin River.
[14] In contrast, as the River exits the Driftless Area "between
Fulton and
Muscatine, [... (
Pool 13)], it flows over or near bedrock".
[Charles Theiling, "River Geomorphology and Floodplain Habitats", p. 1 (]
★ .pdf), USGS, Retrieved July 12, 2007 "The course of the upper Mississippi River along the margin of the Driftless Area of southeastern Minnesota is believed to have been established during pre-Wisconsin time when a glacial advance from the west displaced the river eastward from central Iowa to its present position."
[15]
Other rivers affected by this geologic process are:
'In Wisconsin',
the
Chippewa,
Trempealeau,
La Crosse,
Black, and the
Wisconsin River, along with its tributary, the
Kickapoo River;
'In Minnesota'
the
Whitewater,
Cannon,
Zumbro, and
Root rivers;
'In Iowa',
the
Upper Iowa,
(
Paint Creek may also be mentioned),
Yellow,
Turkey, and
Maquoketa rivers;
'In Illinois',
the
Apple River and
the
Galena River (a.k.a. the
Fever River).
The
Saint Croix River in Wisconsin also needs to be mentioned, as it was the outlet for
Glacial Lake Duluth, forerunner to
Lake Superior, when the eastern outlet was blocked by the continental ice sheet. These rivers all have deep, dramatic canyons giving testimony to the immense quantity of water which once surged through them. The Wisconsin River drained
Glacial Lake Wisconsin.
Glacial River Warren, whose bed is now occupied by the
Minnesota River drained the colossal
Glacial Lake Agassiz. There was ample water to dig a very deep, hundreds-of-miles-long gash into the North American bedrock.
Ecosystem
The climate is
humid continental, displaying both the cool summer and warm summer subtypes as one travels from north to south.
[16] The
United States Department of Agriculture has the region falling mainly in zones 4a and 4b, with the southern fringe being 5a. A few patches in Wisconsin are 3b. The winters in zones 4a and 4b can be quite severe, with the Mississippi freezing over.
Prior to European settlement in the 19th century, the vegetation consisted of
tallgrass prairie and
bur oak savanna on ridgetops and dry upper slopes,
sugar maple-
basswood-
oak forest on moister slopes, sugar maple-basswood forests in protected valleys and on north-facing slopes, wet prairies along the rivers, and some mesic
prairie on the floodplain further back from the river. There were probably also oak forests that contained no sugar maple. Marsh and floodplain forests were also common on river flood plains. Prairie was restricted primarily to the broader ridge tops, which were unfavorable sites for trees due to thin soils and shallow bedrock, rapid drainage, and desiccating winds; all these conditions were also good for carrying fires across the landscape. Prairies also occurred on steep slopes with south or southwest aspect.
Natural fire, long rigorously suppressed, was essential for the regeneration of prairie.
The Midwest Driftless Area Restoration Effort is a multi-agency cooperative effort to restore the landscape.
[17] The main issues are water pollution, from agricultural and animal runoff, and erosion. Water pollution is particularly critical in karsted regions such as this, in that it can degrade or destroy prime cold water fish habitat. Soil erosion, a bad thing in general, presents the
Army Corps of Engineers with a particular problem, in that it requires them to dredge the Mississippi to keep the Mississippi River shipping channels open.
Trout Unlimited is part of this effort, if only because of the superb cold-water streams the region supports. A symposium will be held in October 2007 in
Decorah, Iowa "to share the results of research, management and monitoring work in the Driftless Area."
[18] The
Nature Conservancy is also interested.
Iowa Pleistocene snail
An apparently unique feature of the Driftless Area are small, isolated ecosystems termed
algific talus slopes. These refugia create cool summer and fall microclimates, which host species usually found further north. It contains at least one
endangered species, the
Iowa Pleistocene Snail, and a threatened plant, the
Northern monkshood.
[19] The
Driftless Area National Wildlife Refuge was primarily carved out of the
Upper Mississippi River National Wildlife and Fish Refuge in order to protect these species their associated ecosystems.
The list of protected areas in the region is extensive. Most of them, however, were established for reasons having little to do with being in the Driftless, but nonetheless incidentally locked up some valuable parcels.
A particularly noteworthy annual event is the rising of
fishflies, a kind of
mayfly endemic to the Mississippi valley in the region. These are aquatic insects who rise by the millions as adults to mate, only to die within hours. Attracted to light, they cause an evening's worth of misery, and a day's worth of cleanup in river towns.
[20]
Wildlife is abundant. Opportunities for hunting
whitetail deer and
wild turkey are extensive. Fishing, particularly for
brown trout in tributaries, as well as species such as
channel catfish in the Mississippi is available, while
ice fishing in winter is something of a regional sport.
Some sites unmentioned elsewhere in this article that should be mentioned are
Bixby State Preserve and
Spring Valley Caverns in Minnesota.
Other characteristics
There are very few natural lakes in the region, these being found in adjoinging areas of glacial till, drift and in moraines; the region is extraordinarily well drained, and there no real place where even a pond can naturally form. There are also very few dams in that the valley walls and floors are very often fissured or crumbly, or very porous, providing very poor anchors for a dam or making it difficult to keep any kind of reservoir appropriately filled. There are no real
waterfalls, but some very strong springs bear the name.
A modern, man-made characteristic is the comparatively twisty nature of highways in the region, like in
Kentucky, in contrast to the usually rigid east-west/north-south alignment elsewhere in the Midwest. Here, the roads switchback up stream valleys or travel over ridgetops. The route of
U.S. Highway 20 through the Driftless, and particularly in Illinois, is a good example.
Geographic extent
Minnesota
Corresponding to the
southeast geological region of Minnesota, it begins at about
Fort Snelling just west of
Minneapolis-Saint Paul in the southeastern corner of the state. Starting as a narrow sliver against the Mississippi, it widens to the west as one goes south. The western boundary is the Bemis-Altamont moraine.
[21]
"Rochester plateau">
"Rochester Plateau Subsection",
Minnesota Department of Natural Resources, Retrieved
July 23,
2007 Another more easily located reference to the western boundary is the approximate line of
Minnesota State Highway 56.
The dissection of river valleys along the Mississippi is complete, and one has to travel westward to find remains of the former plateau. The historic vegatation was mixed woodland, with occasional
goat prairies on southwesterly facing slopes.
[22] In the western section is "an old plateau covered by
loess [...] along the eastern border and pre-Wisconsin age glacial
till in the central and western parts. The western portion is a gently rolling glacial till plain that is covered by loess in places."
The counties involved include all or part of
Dakota,
Goodhue,
Wabasha,
Winona,
Olmsted,
Dodge,
Houston,
Fillmore, and
Mower Counties. Aside from the western surburban sprawl of the Twin Cities,
Rochester is the main urban area.
Red Wing, Minnesota is part of the greater
La Crosse, Wisconsin metropolitan area.
Glacial River Warren, in whose bed the
Minnesota River now flows, entered the Driftless Area just downriver from present-day
Minneapolis-Saint Paul, at
Fort Snelling, over
River Warren Falls, "an impressive 2700 feet (823 m) across and 175 feet (53 m) tall, over 10 times as wide as Niagara falls"
[23] (this has since receded to become
Saint Anthony Falls). The region is characterized "by the absence of glacial drift deposits, the sculpted topography, and the presence of the ancient limestone immediately beneath the soil and in cliff outcroppings."
[24] The Minnesota Driftless Area did not reach the Twin Cities or any areas to the north or west of them; rather, the Twin Cities marked the edge of glaciation, with substantial
terminal moraines overlying the region.
[25]
The largest protected area is
Richard J. Dorer Memorial Hardwood State Forest, which contains some state-owned land, but is mostly private, controlled by state conservation easements.
Wisconsin
The Wisconsin portion of the Driftless is almost coterminous with what is traditionally called the
Western Upland of Wisconsin, but excludes the most extreme northwest and southeast portions of the Western Upland (both of these, however, were denuded by catastrophic failures of ice dams holding back
glacial lakes).
The border is defined by the catchment of the
Chippewa River on the north, and somewhat west of the north-south line of the
Wisconsin River. Where the Wisconsin River turns west to join the Mississippi, the area to the south, to include the whole of
Grant County as well as a small portion of
Lafayette County are included.
Karst topography is less prominent in Wisconsin but nonetheless present. The caves are small with cave systems essentially absent. Viroqua City Cave in
Viroqua is one of the better known ones. There is an admission that Wisconsin geologists have been remiss is fully documenting their caves, inside or outside of the Driftless.
[26]
It involves all or part of
Pepin,
Eau Claire,
Buffalo,
Trempealeau,
Jackson,
La Crosse,
Monroe,
Juneau,
Vernon,
Richland,
Sauk,
Crawford,
Iowa,
Dane,
Grant, and
Lafayette Counties.
La Crosse is the principal urban area.
Prairie du Chien, together with the Iowa cities of
Marquette and
McGregor consitute the only other metropolitan area.
Largely rural in character, landcover is forest, farmland, and grassland/pasture; modest wetlands are found in river valleys, and along the Mississippi.
[27] Row crop farming is less encountered than elsewhere in the state.
[28] Away from the Mississippi, the terrain is gently rolling, supporting dairy farms.
The
Wisconsin Dells are the most spectacular part of the Wisconsin Driftless Area, in that their severely and immediately eroded glory represents a glacial dam burst, that of
Glacial Lake Wisconsin, which drained to the east, into what is now
Lake Michigan.
Natural Bridge State Park is located near
Baraboo.
Mill Bluff State Park preserves what were formerly islands in Glacial Lake Wisconsin.
Mirror Lake State Park features a small natural lake in a ravine carved by waters blocked by glacial advances. All of these features are at the eastern edge of the Wisconsin portion of the Driftless.
Iowa
The contrast between what the rest of Iowa looks like and what the Driftless Area presents is often commented upon.
[29] For counties inland from the Mississippi, the evidence is largely confined to the valleys of streams and rivers. It encompasses all of
Allamakee, and part of
Clayton,
Fayette,
Delaware,
Winneshiek,
Howard,
Dubuque, and
Jackson Counties.
Dubuque is the only metropolitan area.
The region is distinct from the "Iowan Erosion Surface to the west and the Southern Iowa Drift Plain to the south."
[30] A line east of the most easterly tributaries of the
Wapsipinicon River defines the
terminal moraine that marks the western boundary of the Driftless, with the catchment of the
Maquoketa River serving as a southern boundary. The most western tributaries of the
Upper Iowa,
Yellow and
Turkey Rivers flow east and south from the vicinity of this moraine.
Outside of
Dubuque, this region of Iowa is thinly populated. In the western section, agriculture and livestock raising are the norm. As one travels east, and as the valleys tumble down to the Mississippi, much of the land is virtually wild, with a great deal of it locked up in public hands. The state maintains an extensive number of wildlife management areas (basically hunting and fishing areas), along with state forests and state parks.
The most impressive area is is on the Mississippi, between
Pikes Peak State Park, opposite the Wisconsin River down to
Guttenberg, where bluffs lining the river reach their maximum height. This is apparently an Iowa continuation of
Military Ridge, a catchment-defining divide in Wisconsin that was used for the
Military Ridge Road, a portion of which is included in
Military Ridge State Trail, both across the River in Wisconsin.
Effigy Mounds National Monument is at the heart of a network of adjacent parks, state forests, preserves, as well as national wildlife refuges, all of which preserve and illustrate the features of the Driftless, where "patchy remnants of Pre-Illinoian glacial drift more than 500,000 years old recently have been discovered in the area."
[31] Additional protected areas are
Cold Water Spring State Preserve near
Decorah and
Maquoketa Caves State Park northwest of
Maquoketa.
Illinois
The Illinois portion is confined mainly to
Jo Daviess County; southern parts of
Carroll County and a tiny portion of northwest
Whiteside County is also included.
[32] The region contains the highest points in the state, of which "the most notable are
Charles Mound and Benton Mound, rising to heights of 1,246 feet and 1,226 feet respectively."
[33] The region "has many sinkholes and sinkhole ponds."
[34]
This portion lacks any real urban center.
East Dubuque is really a part of metropolitan
Dubuque, while
Galena retains its small town Midwest County Seat look.
The valley of the
Apple River has a major canyon, with
Apple River Canyon State Park occupying much of it. The mouth of this river, near
Fulton marks the southern end of the Driftless Area on the eastern side of the Mississippi (''see''
Lock and Dam No. 13).
In popular culture
An interesting connection with the landscape of the region is
Taliesin, home of
American architect Frank Lloyd Wright, who advocated organic integration of a structure with its natural surroundings. Taliesin itself is built from local
limestone and set on the brow of a rugged hill, for the specific purpose of emphasizing its ties to the Driftless Zone of southwestern Wisconsin.
It is also provides the setting and the title for writer
Tom Drury's 2006 novel,
The Driftless Area as well as offering the loction and is the cental image in
Lawrence Santoro's 2007 novel,
Just North of Nowhere.
References
1.
Several names for this area are used. 'Driftless Area' is widely used by both Federal and state sites, and seems to be the common name. 'Paleozoic Plateau' shows up in a number of learned and popular articles and would seem to be on its way to being the preferred name. 'Coulee Region' is primarily a term used in Wisconsin for the greater La Crosse area, and never for other portions of the region in question. Little Switzerland is the common name for the Iowa region of the driftless zone. 'Driftless Zone', 'Driftless Region', 'Driftless Land' are also encountered
2. "Regional Landscape Ecosystems of Michigan, Minnesota, and Wisconsin: Section IV. Driftless Area", USGS, Retrieved July 13, 2007; another government site, "Driftless Area Initiative", USDA, retrieved July 15, 2007, gives "24,103 square miles and 15,425,063 acres"
3. "The Driftless Area", ''Minnesota Conservation Volunteer'', March, 2007 (popular article from the Minnesota Department of Natural Resources (MDNR)), Retrieved July 7, 2007
4. "Yellow River State Forest", Iowa Department of Natural Resources (IDNR), Retrieved July 7, 2007
5. Byron Crowns. "Wisconsin through 5 Billion Years of Change", Wisconsin Earth Science Center, 1976, Wisconsin Rapids, Wisconsin, p. 131,
6. Geology of Green Bay and Lake Michigan lobes (Northern Illinois University), Retrieved July 13, 2007
7. "Geologic and Glacial History", Northern Illinois University, Retrieved July 13, 2007
8.
"Native American use of the Mississippi River", ''Archaeology Education Program'', Volume 22, Number 2, Fall 2004, Mississippi Valley Archaeology Center at the University of Wisconsin-La Crosse, Retrieved July 8, 2007 (
★ pdf)
9. Regional Landscape Ecosystems of Michigan, Minnesota, and Wisconsin, Section IV, Driftless Area, National Park Service, Retrieved July 9, 2007 (A statement from this copyright-free site has been freely paraphrased.)
10. airnav.com, Retrieved August 5, 2007
11. Army Corps of Engineers, interactive site, Retrieved August 5, 2007
12. Watershed Description (of the Upper Iowa River, Northeastiowarcd.org, Retrieved August 5, 2007
13. A.C. Runkel, "Contributions to the Geology of Waubasha County Minnesota", Retrieved July 9, 2007
14. "Geology of Pikes Peak State Park, Iowa Department of Natural Resources, Retrieved July 13, 2007
15. Thomas Madigan, "The Geology of the MNRRA Corridor", p. 26, National Parks Service, Retrieved July 23, 2007
16. Michael E. Ritter,"Humid Continental Climate", University of Wisconsin-Stevens Point, 2006, Retrieved August 11, 2007
17. "Midwest Driftless Area Restoration Effort", FWS, Retrieved July 30, 2007
18. [http://www.tu.org/site/pp.asp?c=7dJEKTNuFmG&b=2776509 “Science in the Driftless Area”, Announcement and Call for Papers, Deadline
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