Glacial Lake Flatwoods (GM-11)
Glacial ice crossed what is now the White River at least twice during the middle to latter part of the Ice Age. This blocked the mouth of the preglacial ancestor of McCormick's Creek and created a lake that extended from near the park entrance southeastward almost to Ellettsville. Water filling the lake came from local drainage and from melting ice. The outlet of the lake was southwestward along the ice margin.
Meltwater brought large amount of silt and sand into the west side of the lake; streams brought mud from the surrounding hills. These sediments, more than 100 feet thick in places, buried most of the former land surface. After the ice melted, normal streamflow began again, draining the lake and leaving behind a flat plain. A good view of the bed of Lake Flatwoods can be seen from the fire tower in McCormick's Creek State Park.
Our Hoosier State Beneath Us: Geomorphology