Roadside Geology of Minnesota

. Roadside Geology of Minnesota steers you over glacial moraines and till plains to some of the state's unparalleled geologic features, such as the Morton Gneiss, once thought to be the oldest rock on Earth; the St. Peter Sandstone, one of the purest sandstones in the world; the banded iron-formation, the source of iron for the Great Lakes steel industry; and the ancient shorelines of Glacial Lake Agassiz, one of the largest glacial lakes ever to have existed in North America.