DEVELOPING GLACIAL LANDFORM EDUCATIONAL MATERIALS FOR THE ICE AGE NATIONAL SCENIC TRAIL IN STRAIGHT LAKE STATE PARK, POLK COUNTY, WISCONSIN
Publications about the glacial geology of Polk County (Johnson, 2000), tunnel channels, and eskers were read in the office. One week was spent in the SLSP area studying glacial sediments and landforms. The best locations to observe glacial sediment and landforms were selected to showcase in interpretive materials.
SLSP contains classic examples of late Wisconsinan landforms. The Superior Lobe played a key role in developing the landforms in the park. These features include a tunnel channel, esker, hummocks, kettles, and a pitted outwash plain formed during the St. Croix Phase about 20,000 cal. yrs B.P.
The Straight Lake tunnel channel was eroded by a subglacial outburst flood near the ice margin. The tunnel channel trends NW-SE and is 12 km long, 0.25 to 0.75 km wide, and at least 27 m deep. After the formation of the channel, reddish-brown, supraglacial sediment of the Copper Falls Formation was deposited inside the channel via a topographic reversal process and obscured the visible channel width along the channel axis. Hummocky topography on the southwestern margin of the tunnel channel contains sandy loam diamicton.
A prominent esker rises up to 15 m above the channel floor and trends parallel to the tunnel channel axis. The esker, a subglacial stream deposit, formed after the erosion of the tunnel channel. The esker is best observed along a 1-km-long segment of the Ice Age Trail northeast of Long Lake and north of State Highway 48. There the sharp-crested, wooded esker towers above the lakes occupying the adjacent parts of the tunnel channel. The esker is present along most of the length of the tunnel channel.
Geological educational materials will be produced in consultation with the WDNR. Materials will include a trail guide, as well as multimedia presentations accessible online via smart phones. The target date for completion of the interpretive materials is May 2012.