On The Shores Of Lake Maumee

It once languished beneath anywhere from 10,000 to 15,000 feet of ice, and later lay hard by the shpres of several glacial lakes. In surface appearance, Washtenaw County looks much as it did 12,000 years ago, when the last glacier disappeared from the area. W i t h the exception of man-made changes, the hills, valleys, rivers, lakes and streams were produced by a series of geologie processes - ice progression and recession, and later, erosión. According to Dr. Donald Eschman, professor of geology and mineralogy at the University of Michigan, examination of the county's topography reveáis a wide range of geologie phenomena that constitute a record of the earth's history for the last 15,000 years. The best description of the area, he points out, is oontained in the Geologie Atlas of the United States - Ann Arbor Folio - written by I. C. Russell and Frank Leverett in 1907. "It's old," says Dr. Eschman, "but it's a case of the first work being the best." Although much of the city was yet to be developed, and the authors'talk about landmarks that no longer exist, the topography is little changed. In the Huron River valley, the delta, or i flat plain of sand and gravel deposits left by receding lake waters, is now wellI exposed by a number of man-made sand I and gravel pits which scar the area. A channel dug by a glacier winds hrough the west side of the city, leads southwest past the University of Michigan athletic field and to tlie east of State Street past the Ann Arbor Railroad tracks. The main U-M campus itself is built on a flat plain at the edge of a moraine, a ridge.of stone and clay deposits formed km Tge of lobW gláciér. ' ' Moraines are conspicuous in Micnigan, md the ridges range in width from a Tiile to several, and in height from 25 to 500 feet. Most in this vicinity, says Dr. Eschman, are no higher than 100 feet. Eastern Michigan University's oldest :ampus buildings, according to geologists Russell and Leverett, sit on top of a sandy ridge that was once a submerged sand bar created at the highest level of a lake which several thousands of years ago covered much of southeastem Michigan. To the north of Ypsilanti, Ridge Road follows a lower ridge of another lake's beach. To the south of the city, Stony Creek Road is built along the edge of the ridge, notes Dr. Eschman. It is also visible off Willis Road, about one-half mile east of the Carpenter Road intersection. Ypsilanti's business district is constructed on the main terrace of a plain deposited when that ancient lake covered the area. Ice receded from this area for the first time nearly 14,000 years ago, explains the U-M geologist, although the dates can't be precisely pinpointed. A second glacier moved into southern Michigan as far as Port Huron 2,000 years later, but rapidly retreated. After the withdrawal of the first ice sheet, the area that was to become Washtenaw County and Ann Arbor had a lovely view of Lake Maumee, which covered northern Ohio and extended a long finger northward to Imlay City in Michigan. (Put that in your hat and smoke it, Toledo!) Many ancient geologie formations are named for the modern-day sites they covered, or in which they were once located. When the ice carne into the picture again nearly 2,000 years later, Lake Whittlesey was formed and later Lake W a rren. All three lakes (including M a u m e e ) covered Detroit, but left present-day Ann Arbor at their western shores. The whole county sits atop the same salt beds that are buried under Detroit, every bit as rich, but at a lower level, making a mining operation here financially unfeasible. "Salt deposits in Michigan occur in saucer-like formations, as do all rock. We Ann ArborNews June 17J973 Section Two Pqges 1 5 to 30 beds within the southern peninsula," explains Dr. Eschman. "Detroit is at the higher edge of the curve, while salt beds here are covered by 700 to 900 feet of rock." But this area is rich in sand and gravel deposits; it is these that help contribute to Washtenaw County's seventh place rank in value of mineral production in Michigan, says Dr. Lawrence Odgen, professor of geography and geology at Eastern Michigan University. "This county is immensely wealthy in terms of sand and gravel, but in order to be commercially useful, the pits must be large, easily accessible to transportation and the product in high demand locally," he added. Inflated surface land values today mean that deposits buried even a few feet below the earth's surface often will be covered with residential buildings rather than extracted for road building and cement mixing. These extensive glacial "droppings" were left by melting streams that flowed away from the ice. The location of these moraines, or accumulations of earth and stone deposited by glaciers, can be seen clearly on a geologie map. The largest moraine in the county, the Fort Wayne, crosses from the northeast, at the Washtenaw-Oakland county line, i to the southwest and continúes into diana. It is visible within the city limits, says Dr. Eschman, in the Oíd West Side área - both Slauson School and Mercywood Hospital sit high atop the moraine. And Fort Wayne Moraine can also be easily identified at the intersection of Scio Church and Wagner Roads. Defiance Moraine, ending near that Ohio city, runs parallel to Fort Wayne Moraine but passes to the southwest of Ann Arbor. Some residents on what is now known as Harbal Drive, s i t u a t e d between Broadway and Plymouth Road, recently petitioned the City Planning Commission to change the name of their street to Defiance Moraine. But a comparison of the city map to a geologie map reveáis that Harbal, while surrounded by Defiance Moraine, sits instead on gravel deposits washed out from the moraine. Fort Wayne Moraine harbors the highest elevation in the county - 1,107 feet above sea level at a point near Pleasant Lake and also constitutes the divide i tween the river drainage systems in the county, although all waters end up in Lake Erie. In the southwest, the moraine separates the drainage of the 150-mile Huron River from that of the longer Raisin River, and in the northeast, the Huron from the Rouge River. Some 134 lakes drain I into the Hurón, 11 into the Raisin. Most of the lakes are small in area, few are ; more than 35 feet deep. The drainage system itself exhibits striking contrasts, the result of conditions produced by ice movement, according to the Folio's text. The northwestern portion contains fewer streams and more swampy and ill-drained land due to a greater proportion of gravelly and loosetextured soil which readily absorbs rainwater and carnes it away underground. The southeastern section is flatter, with fewer lakes, and exhibits a more regular surface. Like moraines, kames, bowlder (boulder) and marshy peat deposits are prominent on geologie maps and appear throughout the county. Kames are small conical hills or short ridges of sand and gravel deposited in holes in glacial ice. When the glaciers ;ceded, they were left at a higher elevación than surrounding surfaces. "Actually, Harbal Drive is on a kame," noted Dr. Eschman. "Another easily identified kame is on the northeast corner of Huron Parkway and Geddes." Outside the city, west of Stadium [Boulevard on Liberty, a Kame is nestled between 1-94 and Wagner Road. Eskers, he says, are less frequently jfound. They result f rom deposits left in I cracks and crevasses that ran far into the lake; as the ice withdrew, eskers [emerge as long, narrow gravel ridges I atop the surrounding plain. The Lima esker, in Lima Township, is the only representative of this class of ■ glacial ridge in the area; it is five miles I long, from five to 20 feet high and from 1 50 to 500 feet wide. Shaped like an elonI gated "L," it passes to the south of Lima I Center. Depressions and poorly-drained rejgions contain thick beds of muck and 1 peat, which have accumulated since the last ice recession more than 12,000 years ago. These deposits are comprised of plant remains, shells of small animáis and some bones of larger ones. Mud Lake in Webster Township and Dead Lake in Northfield Township were once large lakes, report Russell and Everett, but are rapidly filling with peat. The beds may range in depth from 20 to 70 feet. A similar organic matter, marl, or bog lime, was formed when the remains of organisms absorbed lime from the water. But like peat, the deposits aren't large enough to be commercially marketable, although local farmers who find themselves near such bogs use it as fertilizer for their fields. It was such a bog that trapped a prehistorie mastodon, similar to but much larger than its relative, the elephant. Unearthed in 1969 on a Lima Township Farm, the mastodon may be as young as 9,000 years, or as old as 11,000, Dr. Eschman says. "It depends upon which material is used for the dating," explains the geologist. "The o 1 d e s t date comes from material underneath the remains; the younger one from material above the bones." Fossil finds aren't frequent in Washtenaw County; most have been accidental The mastodon bones were uncovered when the Iandowner was digging a pond. Similarly, the skulls of three pecarries - wild pigs - were found b e h i n d Geddes Lake Townhouses in 1971, in a ravine cut during a rainstorm. These bones date around 10,000 years old. Portions of a skeleton of a giant beaver, twice the size of its modern counterpart, were uncovered in a peat bog between Packard Road and the Ann Arbor Railroad tracks around the turn of the century by workers digging a ditch.