Beginning around 15,000 years ago, the Michigan lobe of the Laurentian glacier had retreated back to a line along the
Valparaiso Moraine, from
Wisconsin along a line, inland of
Lake Michigan, southward, around the City of
Chicago, and the southern tip of Lake Michigan, through Indiana, curving northward into the State of
Michigan, only inland from the shoreline. Meanwhile, the Huron-Saginaw lobe had melted back to the north and east along a line in Michigan extending from
Holland eastward through
Kalamazoo to
Jackson. Beginning 14,000 years ago, the glacial lobes had cleared the valley of the
Kankakee River of ice. At this point, the forward movement of ice coming from the north equaled the rate of melting over the summer season. Now stagnant, glacier provided a continuing source of ground rock and soil to the southern edge of the glacier, creating the Valaparaiso Moraine and releasing vast quantities of water, sand and silt into the valley beyond. Lacustrine deposits are those deposited in lake water and only when the lake drains or the land rises, does it become dry land. Most of the soils throughout the counties surrounding the Kankakee are loamy (up to a quarter clay, quarter to half silt with less than half being sand.)[3] The outwash plain is underlain by sand with gravel inter-bedded throughout. The prevailing westerly winds began to treat the 'Lake Kankakee' like the shores of Lake Michigan. Dunes began to form along the south and eastern shoreline. Where ice blocks had been left behind, sand filled the depressions. Runoff from the Valparaiso Moraine built [2] outwash ridges of sand leading into the lake. On the south, the winds built dunes. As the volume of water decreased from the glacier melting northward, the lake slowly drained and filled. Not being able to cut a channel through the limestone ridge in Momence, the Kankakee Lake became 500,000 acres (202,346 ha) of marshland. ==Aeolian sand==