WISCONSIN CROP CIRCLES...NIAGARA ESCARPMENT, 'THE LEDGE' Back to Wisconsin Crop Circle Burlington UFO and Paranormal Research Center Reprinted from Horicon National Wildlife Refuge http://midwest.fws.gov/horicon/hisgeolgy.html Overview What do Horicon Marsh and Niagara Falls have in common? Could it be honeymooners?  They are in fact "married" or connected to each other by the Niagara Escarpment, locally called, "the Ledge."  Generally speaking, an escarpment is a steep ledge or bluff that separates two areas of differing elevation. The Niagara Escarpment is a unique and famous regional landmark, a prominent geological feature. Niagara Escarpment The Niagara Escarpment is a layer of bedrock made up of limestone cliffs and talus slopes. It hugs the eastern edge of Horicon Marsh and extends further south to the town of Iron Ridge and the Neda mines. South of the mines, it disappears as a surface feature, buried by glacial deposits. To the north of Horicon Marsh, it reaches into the town of Oakfield and continues all along the eastern shore of Lake Winnebago to Green Bay and Door County. Overall, in Wisconsin the Niagara Escarpment extends for a distance of 230 miles. It continues north/northeast as an underwater and subsurface feature. It bends underneath Lake Michigan, the state of Michigan, Lakes Huron and Erie, appearing again as a surface feature at Niagara Falls in New York. In other words, the same layer of rock which forms our hills on the east side of the marsh extends 500 miles to the east and is the same rock layer that the Niagara River plunges over to form Niagara Falls. Here in eastern Wisconsin, we live, work, and play on the back side of Niagara Falls! Today, the Great Lakes drain towards the St. Lawrence River and out to the Atlantic Ocean. Imagine instead if they drained towards the Mississippi River. Then Niagara Falls would have been located in Wisconsin, and perhaps called Rock Falls. From New York, the Niagara Escarpment (part of the Michigan Basin) runs through the Appalachian Mountains, goes south into Pennsylvania, Ohio, and Indiana, and meanders back through Illinois, Wisconsin, to West Union, Iowa. It extends north and west into Canada as well. It is like a giant saucer with the western edge in Wisconsin and eastern edge in New York. The Ledge rises up to 200 feet high, but the maximum thickness of this rock layer is 450 to 800 feet depending upon the location. The Ledge's material (dolomitic limestone) is at least 400 million years old. In comparison, the Appalachians are about 300 million years old and the Rocky Mountains, about 70 million. However, the Ledge can be considered even younger because it was reformed at its current location by the last glacier, which receded from this area about 12,000 years ago. Top of Page Geology The endurance of the Ledge is attributed to the erosion-resistant material which forms it. It is made of Silurian limestones and dolomites. Dolomite, the main ingredient, was formed by calcium and magnesium carbonate [CaMg(CO3)2] deposited from decomposing shells and skeletons of primitive sea life which lived in a subtropical coral reef during the Silurian age (over 400 million years ago). So, the Niagara Escarpment was once the edge of a coral reef formed in the warm, clear, shallow, salt waters at the edge of the giant Michigan basin. At the time, this ancient inland sea's basin covered all of what is now lower Michigan, Lake Michigan and eastern Wisconsin. As the Paleozoic Era (600 to 280 million years ago) proceeded, each new layer of sediment was deposited, causing the basin to gradually sink in the middle, and form the sedimentary rock that we see in the Ledge today. Some rock layers are composed of eroded material, others are made of limy material, remnants of marine life. The shallow seas slowly evaporated leaving behind thick deposits of gypsum and salt, the weight of which caused the crust to sink even more. A process called reflux filled the basin many more times, only to evaporate each time in the subtropical sun. There is evidence that an occasional hurricane impacted the environment. Under what is now Michigan and Lakes Huron, Erie, and Michigan, the Niagara Escarpment subsided, causing an upwarping or bending of the bedrock near its margins. The edges of this material were forced to the surface, forming an escarpment at each end (in Wisconsin and New York). When the ancient seas receded, these rock edges were exposed. Most weathered away, but the Ledge kept its cliff edge. A layer of soft, impermeable layer called Maquoketa shale lies beneath the Ledge. It was formed during the Ordovician Period (about 500 million years ago) by great thicknesses of mud which washed in due to erosion from the Appalachian Mountains as they rose to the east. Today, the shale erodes quickly where it is exposed, allowing the dolomite to continually break off and form a new cliff face. This process can be measured at Niagara Falls in miles per century. It is in part because of this relatively soft shale layer that Horicon Marsh was later formed by glacial action. It is also in part because of this impermeable shale bed that many crystal-clear springs form at the base of the Ledge. Fed by precipitation, water flows down slope at and beneath the surface of the Ledge through the dolomite, which is highly fractured into perpendicular horizontal and vertical joints. Springs form at the base of the Ledge where glaciers deposited drift consisting in part of impermeable clays. Water flow continues on to eventually drain into Horicon Marsh or Lake Winnebago. Glacial drift of up to100 feet thick overlies parts of the Oakfield Ledge with its probable karst-like surface on the Niagara dolomite bedrock filling many old river valleys, sink holes, and other highly weathered and fractured geologic features. Besides ancient marine life and the resulting upwarping, glacial ice also molded the Ledge. In some places successive glaciers obliterated it, making it a difficult landscape feature to follow in southern Wisconsin. In other places, glaciers created huge fissures and crevasses. The Ledge would certainly be higher and sharper without the impacts of glacial scouring and bulldozing. Top of Page Plants and Animals Fossils found on the Ledge include brachiopods, cephalopods, crinoids, and corals. They represent creatures that lived in the sea which deposited the materials in the Ledge. Trilobite fossils (Wisconsin's state fossil) are abundant in some old quarries. Part of a giant squid-like fossil found in a Mayville quarry is more than 33 feet long based on comparison to modern squids. Various rocks like calcite crystals, and garnet have also been found. Today, the Ledge is known to harbor many rare species and important natural communities found in few places elsewhere in the world, a remarkable assemblage of plants and animals of global importance. Nine snail species which were thought to have disappeared from northeastern Wisconsin at the end of the last Ice Age have been found living on the shaded Niagara Escapement cliffs and talus slopes, most of them known to live on no more than 50 other sites on earth. One species is unknown to the United States, and another was thought to have gone extinct with the mastodons. One species of snails is so small that it would fit on the head of a pin; the Ledge in Wisconsin holds the largest population of this species. Scientists have also found groups of microscopic organisms living between rock layers that are similar to those found only in Antacrtica and the Colorado Plateau and may be the closest thing on earth to the fossil organisms found in Martian meteorites. Ancient white cedars trees up to1800 years old grow on the Niagara Escarpment cliffs in southern Ontario and in Wisconsin, and some of them are still growing! One tiny white cedar near Toronto, Ontario (same latitude of Oakfield) was 155 years old but only stands four inches tall. It grew only 0.11 grams each year, making it the slowest growing tree ever documented. The oldest trees near Horicon Marsh are red cedars (which are actually junipers). One ancient tree on the edge of the escarpment near Oakfield and another with trunk pieces recovered from the edge of the Ledge near the marsh are only eight inches in diameter but almost 300 years old. Other interesting and unusual plants include spring woodland ephemerals, Canadian yew shrubs, red cedar, walking ferns (they form rhizomes from their leaf tips), bulblet fern, leafcup, fragile fern, cliff brake, northern lungwort, and rare rock cress. Many native animals live on the Ledge, such as wild turkeys, foxes, rabbits, and deer. Some animals make their dens in the rocks at its base. Coyotes stay under the cover of the Ledge during the day, come down to Horicon Marsh to hunt at night, and secretively return to the Ledge by sunrise. Bats find shelter in caves in the Ledge and form nurseries in spring once they return from migration. Hunters set-up goose blinds on the Ledge, and birds who like to follow prominent landscape features during migrations may use the Ledge to navigate. A black bear was seen on the Ledge east of Horicon Marsh on Highway 49 one spring recently, probably "kicked out" of his mother's den and looking for space of his own. That spring, presumably young bears were also seen in Fond du Lac, Waupun, and Columbus. The Ledge is home to the second oldest native forest in North America. The base of the Ledge is dotted by springs, marshes, and lakes, sometimes making access challenging. Because there is too little topsoil on the top of the Ledge plus too much fallen rock at its base, most of the Ledge has escaped farming and has maintained an ancient, wooded habitat. It is one of the most important remaining examples of this diverse habitat type in the upper Midwest and is worthy of our protection. Top of Page The People Evidence of the oldest known humans living in Wisconsin has been found on the Oakfield Ledge: a projectile point over 11,200 years old. The Ledge near Horicon Marsh on up to Fond du Lac is an apparent significant site for religious ceremonies, navigational landmarks, and astronomical observations for ancient Native Americans, still visited today. Sites along it contain petroglyphs (Native American rock art) and markings associated with the solstices and possibly the lunar cycle. The Ledge was first mapped as a prominent land feature in 1836 by a United States Government land surveyor as part of the Wisconsin Territory Survey. The Wisconsin Department of Natural Resources is striving to preserve the Oakfield Ledge. So far, almost 200 acres is protected as state land and is split between two projects: the Oakfield Ledge Natural Area and the Glacial Habitat Area, accessible from Breakneck Road north of Horicon Marsh. Compiled and written by Molly Stoddard. Top of Page Visit, Discover, and Protect the Ledge! There are many places where you can explore the Niagara Escarpment in Wisconsin.  Why not make a driving tour of these sites? Rock and Washington Islands at the tip of Door County are made of Niagara dolomite The limestone cliffs at Peninsula State Park, rising 200 feet above Green Bay. Drive along Shore Road or Skyline Road. On Door County's eastern shore, the cliff slopes into Lake Michigan and allows people to wade long distances into the water. Turn around to face land and you are viewing the Ledge! The Ledge forms the western Lake Michigan shoreline in Door County and makes up the eastern shore of Green Bay. You can see the Ledge around the City of Green Bay, extending southwest to Lake Winnebago. On the northeast shore of Lake Winnebago, you will find High Cliff State Park atop the escarpment. Follow along the east shore to the south, and you follow along the base of the Ledge. Enjoy good views from the west side of the lake as you drive on Highway 41. South of the lake, the Ledge sweeps south and west forming the Oakfield Ledge and the eastern boundary of Horicon Marsh. Get out and explore at new Oakfield Ledge Natural Area and at Dodge County Ledge Park, east of the city of Horicon. Continuing south, the Ledge extends to Iron Ridge and Neda Mine, but then becomes a subsurface feature. (can see by helping with bat survey? Contact Maureen Rowe? Commercial uses for the Ledge's dolomite, and some are still important: dolomite transformed to lime for farm or industrial use, or crushed for road construction. Also used as a building stone.