Geology of Minnesota
Gooseberry Park region
750 million years ago, tremendous volcanic activity in the Lake Superior district was accompanied by the outpouring of hundreds of lava flows having an aggregate thickness of 20,000 feet. After 10,000 cubic miles of material had been discharged, the area collapsed to form the basin of Lake Superior.
Differential weathering of the lava rocks composing the north limb of the basin caused the irregular skyline, as well as headlands of the shore. The lower portions of the flows, being relatively dense and resistant to weathering, form the peaks and points along the coast.
In more recent geologic time, this area has been subjected to repeated glaciation. During the retreat of the Wisconsin glacier 20,000 years ago, while the eastern outlet of the Great Lakes was blocked by glacial ice, the surface of the lake was 530 feet above its present elevation.
Erected by the Geological Society of Minnesota in memory of its first president, Junior F. Hayden, in cooperation with the Department of Highways, State of Minnesota.
(Was possibly going to be replaced by #232 in Minnesota History Along the Highways: A Guide to Historic Markers and Sites in 2003, but has not happened.)