The Valparaiso Moraine is a terminal moraine that forms an immense U around the Lake Michigan basin in North America. It is a band of high, hilly terrain made up of glacial till and sand. It begins near the border of Wisconsin and Illinois and extends south through Lake, McHenry, Cook, DuPage and Will counties in Illinois, and then turns southeast, entering Indiana. From this point, the moraine curves northeast through Lake, Porter, and LaPorte counties of Indiana into Michigan. It continues into Michigan as far as Montcalm County.
It was formed during the Crown Point Phase of the Wisconsin glaciation. At this time the glacier covering the area had grown thin, so it was restrained by the dolomite rock layers of the Lake Michigan basin. Where the glacier stopped, glacial till and sand was deposited, creating the hills of the moraine. After the Valparaiso Moraine was formed, the glacier retreated and formed the Tinley Moraine.
Many towns in northwest Indiana and northeast Illinois are named after the Valparaiso Moraine or the Tinley Moraine. Also, many small creeks or rivers start in the Valparaiso Moraine. The moraine itself was named after the city of Valparaiso, Indiana, where the moraine is narrower and higher than in other places.
The Valparaiso Moraine forms part of the St. Lawrence Seaway Divide, bounding the Great Lakes Basin. Water on one side of the moraine flows into Lake Michigan, through the Great Lakes, and eventually into the Atlantic Ocean via the Saint Lawrence River, while water on the other side flows into tributaries of the Mississippi River, which eventually flows into the Gulf of Mexico.
The Valparaiso Moraine formed as the first major moraine of the Cary substage of the Wisconsin Glacial period (10,000-50,000 years before present). There are three minor moraines that have been identified in northeastern Illinois, the Minooka, Rockdale, and Manhattan. Within the arc created by the Valparaiso Moraine are two younger Cary substage moraines of the Tinley Moraine and the Lake Border Moraine. Younger still is the Port Huron system, which occurs in the northern portion of the Lake Michigan Basin. The Cary substage dates to around 30,000 years before present.
The Valparaiso system includes five moraines north of Chicago. The most northerly reach is to the headwaters of the Fox River in Waukesha County, west of Milwaukee. The moraine angles to the south and east, reaching the headwaters of the Des Plaines River west of Kenosha, Wisconsin, in the county of the same name. The moraine forms a major portion of the eastern divide of the Fox River Basin and then the western bank of the Des Plaines River. The moraine continues southward along the Des Plaines River following the route of the modern Tri-State Tollway (I-294) around the west side of Chicago. Where the Des Plaines River bends to the west and forms the Illinois River, the moraine angles south and east, continuing along I-294 towards Chicago Heights. In this area, the moraine has widened out towards the south and east, becoming a broad plain covering large portions of Will and Kankakee counties.
Turning eastward, the moraine enters Indiana. The moraine is 17 miles (27 km) wide as it passes through Lake County, Indiana, covering nearly half of the county's midsection. As it passes through Porter County, Indiana, it is under the city of Valparaiso, from which it derives its name. Through Indiana, the moraine forms a "continental divide" between the drainage of the Great Lakes and the Gulf of Mexico by the Mississippi River.
The moraine then turns northeast, passing just north of La Porte, Indiana, through the county of the same name. Upon entering Michigan the moraine forms much of the shoreline of Lake Michigan northward through St. Joseph. From here northward the moraine angles more eastward, missing Holland and passing through Grand Rapids, finally ending in a mingling of inter-lobe moraines about 50 miles (80 km) northwest of Grand Rapids in Montcalm County.
The Lake Erie basin has two moraines of the same age as the Valparaiso Moraine, the Mississinawa Moraine and the Union Moraine. These moraines formed from the Lake Erie Lobe of the continental glacier.
The Mississinawa Moraine begins in Ohio east of Lima in Hardin County, then running southwest in a shallow arc to the south of Grand Lake St. Marys and St. Marys in Mercer County towards Fort Recovery, Ohio. Just west of Fort Recovery, the moraine again arches southward towards the Mississinewa River in Jackson County, Indiana. The moraine follows the eastern bank of the river northwestward to where it enters the Wabash River at Wabash, Indiana. Angling towards the north and a little east, the Mississinawa moraine merges with the Packerton Moraine north of the Eel River in Whitley County near Columbia City. The moraine does not end here, but continues in a northeasterly direction through the three corners area of Michigan, Indiana, and Ohio until reaching Ann Arbor, Michigan, where numerous moraines intermingle.
The Union Moraine begins in Ohio, east of Bellefontaine and the highest point in that state (Campbell Hill, 1,549 feet (472 m)), towards Greenville in Darke County. Traveling southwestward and arcing a little northward, the moraine reaches Union City, Ohio, for which it is named. From here, it travels almost directly westward to Muncie, Indiana. From Muncie, the moraine runs northwest, ending in the bluffs overlooking Pipe Creek at Bunker Hill, Indiana, just south of Peru on the Wabash River.
The Fort Wayne Moraine is considered contemporary to the last stages of the Valparaiso Moraine. Centered on Fort Wayne, Indiana, the northern leg of the moraine is mostly overlaid by the younger Wabash Moraine angling northeastward through Williams County, Ohio. It only becomes identifiable in Lenawee County, Michigan, south and northeast of Adrian before ending in the intermingling of moraines around Ann Arbor. The south and eastern leg of the moraine follows the northern bank of the St. Marys River into Ohio. At the north bend of the St. Marys River, the moraine arcs northeastward through Lima, continuing in a northward arc to reach north of U.S. 30 in Hancock County to pass through Upper Sandusky, again bending to the north to end 15 to 20 miles (24 to 32 km) to the northeast.
Glacial features, north to south from Lake Michigan:
- Moore, Powell A. (1959). The Calumet Region: Indiana's Last Frontier. Indiana Historical Bureau.
- Hough, Jack L.; Geology of the Great Lakes; University of Illinois Press, Urbana; 1958, pg 97
- Moore, Powell A.; The Calumet Region, Indiana’s Last Frontier; Indiana Historical Collections, Vol. XXXIX; Indiana Historical Bureau, Reprint 1977
- Environmental Setting of the Upper Illinois River basin and Implications for Water Quality; Water-Resources Investigation Report (WRIR) 98-4268, Dept of the Interior, U.S. Geological Survey; Urbana, Illinois, 1999
- Glacial Map of the United States East of the Rocky Mountains, U.S. Geological Survey, Department of the Interior
- Rand McNally Road Atlas, Rand McNally Co; Chicago, IL,
- Schoon, Kenneth J., Calumet Beginnings, 2003, Indiana University Press p. 20-22 ISBN 0-253-34218-X