Glaciation During the Quaternary Period                                SEE: Albert Crane's Glacier Rock

About two million years ago great ice sheets started to move southward, from various centers of refrigeration and accumulation in Canada, over the northern half of North America as far south as the Missouri and Ohio rivers. This vast sheet of ice slowly, relentlessly, plowed over the Great Lakes region, pushed onward by the ever thickening mass of ice on the Canadian plateau until it was brought to a standstill at its southernmost margin. The ice never advanced farther south than about 1600 miles away from its accumulation zone in Canada, or roughly to the position of the present Ohio River, whose course in part was established along its border.

In its relentless, crushing advance the huge Labradorean ice sheet rasped, scraped off, and absorbed into itself the residual soil and loose rock masses which had covered the old rock surfaces of the state. The ice froze onto, plucked, tore huge
blocks loose from bed rock, clutched them in its icy grip, embedded them in its glacial mass, and used them as tools to erode — scrape, gouge, rasp, and scratch the surface over which it moved. It used fine sands and clays to sand, smooth, and polish not only the bedrock surface but also the boulders churned within the mill of moving ice.

THIS image (right) shows the maximum extent of the ice sheet in our region. Note that Michigan was totally covered by ice at this time.

High areas of hard, resistant rock were smoothed off and in some localities (especially the western UP) were highly polished by the grinding, rasping, rubbing, of the debris-filled Wisconsin ice. In many places the smooth rock pavement is scored with scratches and grooves cut by the sharp rock tools held at the bottom of the glacier and given power by the weight and movement of the ice. These markings, or striations, wherever preserved on the old rock floor tell the direction of ice movement, since they always parallel the direction of ice advance. In deep valleys the advancing ice dumped some of its load and pressed the debris almost to hard firm rock by its own sheer weight.

The land and water surfaces of Michigan are largely the result of the sculpturing, erosion, and deposition of materials during the last two million years ­the Pleistocene Epoch. Several stages of the continental glaciation affected the state, but the most important was the most recent Wisconsin stage, which retreated from Michigan about 9,500 to 15,000 years ago. Today's water, landforms, and soil characteristics and patterns are related to the nature and results of the glacial processes. The image left shows the extent of the Laurentide ice sheet at about 14,000 years ago. ("Laurentide" is the name given to the ice sheet that advanced into Michigan from the Laurentian region of Canada.) This time period does not mark the maximum extent of the ice in the Great Lakes region (which occurred about 18,000 years ago), but it does show nicely the major lobes of ice that comprised the ice sheet.

The glaciers advanced into the Great Lakes region as a series of ice lobes, each lobe seeking out the lowest preexisting spots on the landscape. To the various glacial lobes we have given the names of the Great Lakes and bays which eventually occupied the enlarged depressions after the ice had disappeared.

Thus we had the Superior Lobe, with the Keweenaw lobe as an offshoot; the Lake Michigan lobe, with its Grand Traverse and Green Bay appendages; the Huron Lobe, with its subordinate Saginaw Lobe which played as important a part as its parent; and the Erie and Ontario Lobes. Slowly the lobes made their way southward out of the old widened river valleys and during the climax of the last, or Wisconsin stage of glaciation, all the lobes were welded together south of the Great Lakes region, and advanced southward as one broad sheet of ice or glacier with slightly lobate front. Not until the ice melted back into southern Michigan did the ice front again become separated into distinct lobes.


The ice lobes became, perhaps, more apparent during retreat than they may have during the advancing phase of the glacier. The image right shows the ice lobes as they would have looked about 14,000 years ago.

As we examine the methodical and sometimes discontinuous way that the ice margin retreated from Michigan, we must keep in mind that the main lines of evidence we have for this story come from the end moraines left behind AT those margins.

Probably the first lobe to really begin its retreat was the Saginaw lobe. The Saginaw lobe was thinner than the Lake Michigan and Erie lobes and therefore melted faster and was the first to begin its retreat. Its first halt after uncovering an area of four or five townships in St. Joseph and Cass counties was near Sturgis, where it built the first and oldest moraine in Michigan — a line of hills passing through Sturgis and bordering the triangular area first uncovered.
This hilly ridge has been named the Sturgis moraine. From this outpost the lobe receded step by step into the Saginaw Valley, and at each halt built a moraine, so that its retreat across Michigan is marked by a succession of more or less parallel moraines closing in on Saginaw Bay from the south, with their ends tied to the massive moraines of the Erie lobe in the east and the Lake Michigan lobe in the west.
After its brief stop at Sturgis, rapid melting caused the Saginaw lobe to retreat to the position of Tekonsha where it built the slender Tekonsha moraine. Further retreat brought the Saginaw ice front to the position of the large and wide Kalamazoo moraine about 14,800 years ago. Here it halted long enough to build up a high, wide, massive, very hilly range. The Kalamazoo moraine extends from Hastings south and east through Marshall to Devil's Lake in Lenawee County where it connects with Mississinawa moraine which outlines the outermost position of the Erie lobe in southern Michigan. On the west the Kalamazoo moraine of the Saginaw lobe unites with the moraine also called Kalamazoo, which the Michigan lobe was making at that time, extending from Hastings through Kalamazoo and Cassopolis. This Outer Ridge of the Kalamazoo moraine marks the most easterly extent of the Lake Michigan lobe. From this time the pattern of moraines records the retreats and halts of all the glacial lobes — Erie, Huron, to the east, Lake Michigan in the west, and the Saginaw lobe between, and the Superior lobe in the north.

Renewed melting of the Saginaw lobe caused its front to recede to the vicinity of Charlotte where it built the Charlotte moraine. This ridge may be traced to the vicinity of Grand Rapids where it ties in with another morainic system of the Lake Michigan lobe — the large and wide Valparaiso moraine, which comes north from Indiana. The Michigan lobe had retreated from the position of the Kalamazoo moraine to make a long stand in the west, during which it built up the high Valparaiso moraine which marks the border of the Lake Michigan lobe from Indiana to central Wexford County. This moraine is a typical "knob and kettle" formation. The highways of the region lead from valley up over knobby hill or high steep knoll, from whose summit one may look over a bumpy country of hill and kettle-like basin filled with lake or swamp or drained to rich, dark mucks.

Retreating from the Valparaiso moraine, the Lake Michigan lobe halted long enough before it retreated into the Lake Michigan basin to build the Lake Border morainic system at 13,300 years ago, a complex of low ridges which closely follows the margin of Lake Michigan. Meanwhile, the ice over the eastern part of the State was building the massive West Branch and Gladwin moraines north of the Grand River. But south of the river the rapidly retreating Saginaw lobe was building only slender moraines which fray out from the West Branch-Gladwin moraine and mark the halts of the Saginaw lobe as it back-stepped into the bay. This group of slender moraines does not have the rugged topography of the moraines to which they are tied at either end, because the Saginaw lobe was thinner and had cleaner ice than did the other lobes. Named in order of development from the vicinity of Lansing northward, the thin, low moraines of the Saginaw lobe are: Lansing (viewable from the intersection of Farm Lane and Mt Hope, just look due south at the rise of hills on the horizon), Grand Ledge, Ionia, Portland, Lyons, Fowler-St. Johns, Flint and Owosso.

After the next retreat the Lake Michigan-Saginaw-Huron lobes then readvanced back into the state. This readvance was a large one, and occurred over the entire Great Lakes region; it is called the Port Huron advance and it constructed the Port Huron moraine.

The same determined stand was taken along the entire glacier front from east to west, so that this moraine has been traced more precisely than any other and stretches from the Genesee Valley in New York to Lake Michigan north of Ludington. This advance took place at about 13,000 - 12,000 years BP.

The glacial features of the UP were formed in large part by the Superior lobe of the glacier. This mass of ice was directed into the Superior Basin from the northeast, and pushing out over the rim of the basin; it covered the greater portion of the Northern Peninsula. The Superior lobe also left end moraines, and in the western part of the peninsula complicated the pre-glacial rugged topography by filling some of the gorges with drift, diverting the courses of some streams and damming others by building morainic dams across their courses. Lake Gogebic lies in the channel of a stream that once flowed to the north but its headwaters were cut off, dammed by a moraine, and Lake Gogebic formed.

By: Randall J. Schaetzl   Michigan State University