Cactus Hills

Cactus Hills. . Early geologic research into glacial deposits indicated that during the Ice Age there were only four periods of glaciation in North America. Today fourteen episodes of glaciation are recognized. Deposits from five of these episodes are found in Minnehaha County. From the most recent to the earlier episodes they are named: late Wisconsin, Illinoian, and pre-Illinoian 1, 2, and 3., The Cactus Hills are composed of sand and gravel deposits left more than 300,000 years ago by streams flowing from a receding pre-Illinoian glacier. They mark the point where the ice front stalled before continuing its retreat., Originally the outwash deposits were more extensive, but subsequent erosion by late Wisconsin meltwater removed much of the original deposit. Remnants of the deposit, of which the Cactus Hills are a part, are found at higher elevations on both sides of the Big Sioux River valley., Geologically the Cactus Hills are part of a series of kames and terraces extending to the northeast toward Garretson, SD.