Nestled in northwestern Iowa
is an area known as the
“Iowa Great Lakes.”
Historically, this region has been a popular vacation destination, yet few people realize it is also a showplace of geologic features that reflect the state’s most recent contact with glaciers. In Dickinson County, the curved, boulder-strewn shores of Gull Point State Park jut outward between Miller’s Bay and Emerson’s Bay into the deep waters of West Okoboji Lake. The park itself is surrounded by clusters of knobby hills, smaller lakes and bogs, and abundant sand and gravel deposits – all reflecting the last advance of glacial ice into Iowa.
Gull Point State Park and the Iowa lakes region occur along the southwest edge of an ice sheet that surged southward about 13,500 years ago, halting at what is now the city of Des Moines. This ice stagnated across the landscape and was followed by several smaller readvances over the next 1,500 years. The resulting topography in the lakes area is especially eye-catching because the younger glacial advances overlapped the older ice and merged to create widespread areas of high-relief, hummocky, “knob-and-kettle terrain.” The irregular hills of glacial debris associated with these compressed ice margins are laced with sloughs, bogs, and wetland “potholes” that formed in direct contact with the slowly disintegrating ice.