Kettle Moraine Scenic Drive
State Forest Geological History

Some 20,000 years ago, two lobes of a great ice sheet met along a line extending northeast from Richmond in Walworth County through the Oconomowoc Lake country to Kewaunee County. One lobe moved down what is now the Green Bay-Lake Winnebago area. Spreading under tremendous pressure, the two lobes met and in the encounter, large blocks of ice were broken off and buried in the glacial deposit or till. As the ice melted, "kettles" were formed, some only a few yards across, others 100 to 200 feet deep.

The ice moved under great pressure, changing shape rather than sliding across the face of the land. As it changed shape, large amounts of rock, gravel, sand and silt were picked up and carried along by the glacier. When the ice melted, this material was deposited, in some instances, across glacier-formed valleys. Some "kettles" were formed this way.

The Kettle Moraine is an area of varied topography--parallel, steep-sided ridges, conical hills and flat outwash plains, mostly composed of sand and gravel. Many of the conical hills are conspicious. Holy Hill reaches an elevation of 1,361 feet above sea level and some 340 feet above the stream valley to the east. Sugar Loaf or Pulford Peak (elevation 1,320 feet) is 320 feet above Pike Lake. Lapham Peak (elevation 1,233 feet), where there is a picnic area and observation tower, is 343 feet above Nagawicka Lake.

Similar detached sand and gravel conical hills, called kames, characterize the moraine throughout much of its extent. Some of these kames are cones formed beneath the glacier by surface streams which fell through holes in the ice. The undulating level-topped, narrow ridges called eskers were probably deposits in open cracks (crevasses) in the ice. In some areas the outwash terraces are pitted due to the melting of buried ice masses.

The Kettle Moraine area rises to 300 or more feet above the lands to the east and west yet is not a continuous divide. Maximum thickness of the drift is not known because few wells reach bedrock. It is possible that the drift reaches a thickness of 500 feet in some places.

Limestone underlies much of the Kettle Moraine. This formation is 450 to 800 feet thick and dips gently eastward. Its western edge or escarpment extends from Washington Island to the Illinois line near Walworth. It lies 20 miles to the west of Kettle Moraine at Greenbush, is completely covered by the moraine in the Waukesha County area, and is 8 miles east of the moraine at Elkhorn. Because of the cover of drift, there are few outcrops in the moraine.

Lakes, of several origins, add greatly to the attractiveness of the Kettle Moraine. With the exception, of Pewaukee Lake, which lies in a preglacial valley blocked on the west and east by drift, all lakes in the Oconomowoc area occupy kettles. Long Lake, Big Cedar Lake and Elkhart Lake occupy preglacial valleys between morainic ridges. These valleys were probably occupied by ice blocks and escaped being filled by glacial drift.