Geology
The limestone was laid down 500 million years ago as organic sediments settled to the bottom of a shallow sea that covered much of the Midwest. Much later Glacial River Warren carried torrents of runoff from the melting glaciers of the last ice age. Flowing out of Lake Agassiz, Glacial River Warren carved the Minnesota River valley and the Mississippi River Valley, leaving steep bluffs along the latter's banks. At times Glacial River Warren overflowed its bed and Garrard's Bluff would have been an island. The area is near the northern extreme of the Driftless Area of Minnesota, a region that remained unglaciated during the phases of the last ice age.
In the present day, a creek flows through the eastern end of the park into Lake Pepin. Wells Creek carries substantial amounts of sand eroded out of the nearby hills. As it hits the slow-moving river water, it drops its sediment load, creating a delta and Sand Point, a sand spit jutting perpendicularly out into the lake. Downstream the Chippewa River performs the same action on a larger scale. This sediment blockage is what causes the Mississippi to widen into Lake Pepin.
Read more about this topic: Frontenac State Park