April 15, 2010

Northeastern Morainal Division

This week, we look at the third natural division, the Northeastern Morainal Division. This area was the last area of Illinois covered by glaciers during the ice ages and encompasses Cook, Lake, McHenry, DuPage, and Boone Counties as well as parts of Kane, Winnebago and Will Counties (map).

Only 10,000 years ago, this division was covered by glaciers. Glacial landforms such as kames (conical mounds of glacial debris), moraines (long ridges of glacial debris), and eskers (a ridge of sand and gravel from an ancient embedded glacial stream) are common. The old bottom of Lake Chicago (the ancestor of Lake Michigan) is now occupied by the city of Chicago. Sand dunes of varying sizes occur along Lake Michigan. The soils are derived from lakebed sediments, peat, beach deposits, and glacial drift, and range in texture from sand and gravel to silty clay loams. In addition to a variety of prairie and forest communities, this division also has fens (wet prairies with an alkaline water source associated with calcareous springs and seeps), marshes (common because of the poorly drained soils), sedge meadows, and bogs. The only true bogs in the state and all of the state’s glacial lakes are found here, as is a natural beach-and-dunes association. The area is divided into four subsections—the Morainal Section, Lake Michigan Dunes, Chicago Lake Plain, and Winnebago Drift. To experience this division, visit Illinois Beach or Moraine Hills State Parks or Volo Bog State Natural Area.