Follow The Links Below To Learn More About The Background of the Ancient Glacial Lake Wisconsin Project
Geology of the Central Sands Region
Natural History of the Central Sands Region
Wildlife of the Central Sands Region
Imperial Multimedia
Geology of the Central Sands Region
The landscape of Central Wisconsin as we know it today is entirely attributable to the recent geological past. During what is known as the “Wisconsin Glaciation,” a lobe of the Laurentide Ice Sheet, a massive ice sheet that covered thousands of miles, stretched into central and southeastern Wisconsin. This, the Green Bay Lobe, reached as far south and west as the Baraboo Hills, effectively forming a dam of the ancient Wisconsin River to the east and south. Behind this glacier to the west, a massive pro-glacial lake formed. This lake is what is known as “Glacial Lake Wisconsin.” The shoreline of the glacial lake changed over time, expanding considerably as the glacier began to melt. The southern shoreline of the lake is the area of Wisconsin that remained unglaciated—the “Driftless Area” to the south and west. The original drainage to the southeast through and around the Baraboo Hills remained blocked for about 5,000 years; when the lake reached a certain size and level, it drained north and west down what is today a tributary (East Fork) of the Black River, eventually draining into the Mississippi River.
At its greatest extent approximately 15,000 years ago, the lake was over 70 miles long and was over 160 feet at its deepest. About 14,000 years ago, as the glacier was melting, there came a moment where the glacier was no longer damming the water behind the Baraboo Hills, and the lake began to drain southward into what is today the Wisconsin River valley. The sudden draining of the eastern (Lewiston) basin of Glacial Lake Wisconsin resulted in the draining of all the basins simultaneously—and very rapidly! The vast volume of flood water, carrying with it large amounts of sand and soil, passed rapidly through a narrow gap in the soft sandstone near what is today known as the city of Wisconsin Dells. As the water cut deeper and deeper into the sandstone layer, the magnificent Dells that can be viewed today were formed. Similarly, the sandstone bluffs of the Lower Wisconsin River were scoured, carved and etched by the large volume of flowing water during the same flood event. Geologists have surmised that this “catastrophic” draining of Glacial Lake Wisconsin may have occurred in only a matter of several days!
Once the glacier melted and the glacial lake drained, what remained in its place was a vast lakebed with deep sandy deposits. What were once islands in the deep glacial lake now are spires of erosion-resistant sandstone that dot the Central Wisconsin landscape. Many such bluff formations can be seen in Adams County and along Interstate I-90/94 in the Camp Douglas area. Sand, stone and boulders remaining after the glacier melted were deposited in an outwash plain and moraines on the eastern shoreline of the glacial lake near what is today Interstate 39. Much of the old lakebed was flat with standing shallow water and convoluted drainage rivers. It was in this lakebed that extensive wetlands formed in the intervening millennia. The eastern edge of the lakebed was higher and dryer. Today, the ancient Glacial Lake Wisconsin landscape is a mosaic of agricultural lands, woodlands, waterways and wetlands.
To the east of the ancient Glacial Lake Wisconsin, a more complicated story of glacial deposits is seen on the landscape. Former river channels became filled with glacial rubble, and depressions in the landscape held water that eventually became rich wetlands. The north-south moraines are characterized by mixed layers of sand, gravel and boulders, and constitute the rolling hills that can be found east of I-39 going north from Portage and Wisconsin Dells to Stevens Point and beyond. The Ice Age National Scenic Trail traverses much of the moraine-covered landscape east of the former Glacial Lake Wisconsin.
Natural History of Central Sands Region
Wisconsin has been divided into 16 distinct “ecological landscapes” by Wisconsin Department of Natural Resources ecologists. Each ecological landscape has its unique characteristic flora and fauna that make them distinctive. Climate, soil and topography play important roles in determining what plant communities will grow where.
In Central Wisconsin several of those ecological landscapes can be directly attributable to recent geological events. The ancient glacial lake impounded behind the advancing glacier 19,000 years ago (see section on “Geology”) and the subsequent melting of that glacier approximately 14,000 years ago, left behind a flat sandy lakebed and outwash plain bounded to the south and west by the unglaciated part of the state (Driftless Area), and to the north and east by the undulating glacial moraine deposits. This region of Central Wisconsin comprises the “Central Sand Plains” and “Central Sand Hills” ecological landscapes. The region we are dubbing the “Ancient Glacial Lake Wisconsin” covers much (but not all) of eleven counties within the Central Sand Plain and Central Sand Hills ecological areas.
The Central Sands Region of Wisconsin was once characterized by the most extensive and diverse wetland communities of the entire state, including enormous tamarack bogs, sedge meadows and wet meadows. Emergent plant communities, alder thickets and swamp forests lined the extensive waterways—the Wisconsin River and its tributaries draining south, and the Fox River and its tributaries draining north and east.
Although countless acres of wetlands were logged, drained, ditched, tiled and destroyed at the end of the 19th and early 20th Centuries, primarily for agricultural production, extensive wetland systems have subsequently been protected and restored by federal, state and county governments over the intervening century. The Central Sands Region is today rich in vast and diverse public wetlands that harbor some of the state’s most iconic wildlife species—sandhill and whooping cranes, trumpeter swans, waterfowl galore, bald eagles and osprey, herons, egrets, bitterns, and countless shorebirds and songbirds. The “crown jewels” of protected wetlands in the region include the Necedah National Wildlife Refuge, Sandhill State Wildlife Area and Meadow Valley Wildlife Area. Together these federal and state properties, along with county lands, comprise almost 150,000 acres of public lands—open to you!
Due to an extensive history of drainage, ditching and continous irrigation for intensive agricultural practices in the eastern portion of the Glacial Lake Wisconsin lakebed, few original wetlands remain. Instead, many of the former wetland landscapes are now dominated by wet grassland communities that together comprise the Central Wisconsin Grassland Conservation Area. Thousands of acres of these grasslands have been purchased by private and public entities, and are today managed for grassland birds and wildlife. The rare and spectacular prairie chicken makes these grasslands home, as do countless other species, including marsh harriers and short-eared owls, diverse grassland sparrows and innumerable songbirds.
The central wetlands of the Glacial Lake Wisconsin region have become the largest cranberry growing region of the state and country. Native wetlands that were converted to “cranberry bogs” are maintained by flooding the fields several times a year, once at harvest time and once just before freeze-up. To maintain the beds, impounded waterways are created on cranberry lands. These impoundments now serve as important wildlife habitat.
On the higher sandy plain and hills of the ancient glacial lake bed, jack pine and scrub oak dominated the landscape, with a ground layer of dry prairie/savanna and barrens plants. Natural and human-caused fire played an important role in maintaining an open oak woodland—savanna—landscape through much of Central Wisconsin. During periods of drought and frequent fire, the landscape was kept more open. Fire stimulates the opening of jack pine cones, allowing the seeds to germinate in the resultant bare ground. During wetter periods with less frequent and smaller fires, the barrens and dry prairie gave way to dominance by the jack pines and oaks, and subsequently became more wooded. This fire-driven dynamic in the region’s plant community persisted for millennia, until the advent of European settlement in the 1800s.
The western portion of the Central Sands Region was originally dominated by extensive pine and oak forests attributable to a slight increase in elevation from the ancient glacial lakebed. Historically, the largest “pinery” (white pine forest, for harvest) for the entire state was in Jackson and Clark Counties. Today, in those two counties alone, more than 320,000 acres are maintained and managed as state and county forestland—public lands that are waiting to be discovered!
Erosion-resistant pillars of sandstone rise prominently above the sandy lakebed of the former Glacial Lake Wisconsin. These rocky outcroppings were once islands in the glacial lake, as their sides show the effects of millennia of wind and wave action. A number of these bluffs now harbor remnants of the original Wisconsin vegetation that was once widespread in the region; sites with important rare and threatened plant and animal species or geological importance have been classified by the state as State Natural Areas. Natural Areas have the highest level of protection and are managed and maintained with a priority to protect the original plant and animal species. As you explore the region, you will encounter many state natural areas that represent our most pristine ecological lands; you may visit, but tread cautiously, as some have rare species found nowhere else.
Wildlife of the Central Sands Region
The diverse landscapes of the innumerable and extensive public lands and waters of Central Wisconsin provide habitat for abundant wildlife. The region is a true Mecca for bird watchers and wildlife observers. Some of the state’s most iconic and spectacular species thrive here—from timber wolves and badgers to bald eagles and prairie chickens. The vast wetlands and waterways harbor countless ducks, geese, herons, egrets, terns, shorebirds and other wetland species while the woodlands are rich with hawks, woodpeckers and colorful songbirds. The extensive grasslands of the Central Sands region provide habitat for dwindling grassland birds like Henslow’s and LeConte’s sparrows, harriers, short-eared owls and meadowlarks. The sandy scrubby barrens rich with lupine are ideal habitat for the federally-endangered Karner blue butterfly (and there is an annual Karner Blue Butterfly Festival in Black River Falls!)
A number of Wisconsin’s rarest species have their largest population in the region, including trumpeter swans, whooping cranes, prairie chickens, red-headed woodpeckers, Kirtland’s warblers and the Karner blue butterfly. A very rare and little known rattlesnake, the Eastern Massasauga, a state-endangered species, likely inhabits the forested river bottoms of the region. State threatened wood turtles and a species of “special concern,” the Blanding’s turtle, prosper in the remote waterways, and the elusive American bittern and black terns can be seen in abundance in some of the area’s large wetlands.
Necedah National Wildlife Refuge boasts a bird list with 230 species. A visitor to the Refuge is likely to observe whooping cranes, trumpeter swans, harriers, bald eagles, great blue herons and egrets, deer, muskrat and possibly otters on any given day in spring, summer or fall. The careful observer will spot the less conspicuous shorebirds on muddy shorelines, swamp sparrows and common yellowthroat warblers in the shrubby wetlands and red-headed woodpeckers and whip-poor-wills in the oak savannas that the Refuge staff is actively managing for these species. A healthy wolf population thrives at Necedah and the nearby Black River State Forest, but they are wary of humans and are rarely seen.
The reintroduction of trumpeter swans and whooping cranes in Wisconsin are true wildlife success stories. Both species had been extirpated from the state almost a century ago due to hunting and habitat destruction. Through dedicated and tireless conservation efforts, both of these elegant white birds now make Wisconsin home. Starting in 1986, trumpeter swan eggs were brought from Alaska and the young were raised in captivity; using various techniques, young swans were introduced to large wetlands of northern and central Wisconsin. Eventually, swans adopted their new landscape and have become residents once again of Wisconsin’s wetlands. Whooping cranes, too, have been reintroduced into Wisconsin starting in 2000, and a small population (ca. 100 birds) exists in Central Wisconsin, the majority near or in Necedah National Wildlife refuge.
The angler will find unlimited opportunity to catch fish throughout the Central Sands Region. Trout streams abound, as well as lakes and rivers for game or pan fish. The vast Petenwell and Castle Rock Flowages offer endless fishing opportunities. A handful of extensive State Fishery Areas owned and managed by the Wisconsin Department of Natural Resources are featured on this website.
No matter your preferred “habitat,” you’re sure to see and discover abundant wildlife in the Central Sands region!
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