The water came from the melting 'Valparaiso glacier', the glacier that deposited first the Manhattan moraine and then other moraines to the northeast in the Valparaiso morainic system. Some hills are solely glacial drift others may be entirely of limestone. Some areas are underlain by bedrock near the surface in other areas it can be 100 feet (30 m) deep. Pre-glacial erosion of the surface of the bedrock created an irregular surface, allowing the glacial drift to vary in depth over short distances. The area is underlain by dolomite bedrock of Silurian age. Both the Ohio and Mississippi Rivers appear to have had their courses altered by the Kankakee Torrent, with the Ohio being pushed further south and the Mississippi further west.ĭesigned from 1942 - Illinois Glacial Lakes by George, E. The effects of the Kankakee Torrent were not limited to northeast Illinois. The Illinois State Geological Survey reports that Rock Creek is cutting through the dolomite bedrock to the waterfall point, upstream of its confluence with the Kankakee River, at the rate of 3 inches (76 mm) per year. This effect is most evident where Rock Creek joins the Kankakee. This is because the flood carved the Kankakee far deeper than would normal river erosion, and the erosion of the bedrock along the slow-moving tributaries has never caught up. Along much of its course, tributaries enter the Kankakee over waterfalls, a phenomenon known as 'hanging tributaries'. The Kankakee River State Park encompasses all of the types of features that formed as a result of the catastrophic flood event. The Kankakee River also bears several features that are direct results of the catastrophic flood. When European settlers arrived, one remaining sign of these deposits were sand dunes located along parts of the flood's course. Sand prairies exist where the massive flood waters stopped their movement and deposited large quantities of sand. Another, very different, geologic effect left over from the Kankakee Torrent is the existence of 'sand prairies'. Most notable today is a region in north-central Illinois known as Starved Rock while most of Illinois is located on a low-lying plain with little variation in elevation, Starved Rock State Park features several canyons which were created in the Kankakee Torrent. Both the Kankakee River and Illinois River largely follow paths carved out by the torrent, a process that is believed to have taken only days. The Kankakee Torrent was responsible for extensive modification of the Kankakee River and Illinois River river valleys and landforms characteristic of megaflooding. Michigan ice lobe at the Valparaiso Moraine location during the Pleistocene Ice Age.

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