Glacial Past of Iowa
The seven major landform regions of Iowa Iowa has a very diverse geological history. An area’s landscape can reveal information about the history and different events that have happened over a period of time. Iowa has a geologic past that has created incredibly diverse environments, which have been modified at different times throughout its history.
There are seven major landform regions of Iowa that give Iowa the landscape it has today. These regions are the Des Moines Lobe, Loess Hills, Northwest Iowa Plains, Iowa Surface, Paleozoic Plateau, Missouri Alluvial Plain, and the Southern Iowa Drift Plain. The landscape in Buena Vista County is a mixture of the effects of both the Des Moines Lobe and the Northwest Iowa Plains.
Wisconsinan Glacier and Des Moines Lobe
Edges of the Wisonsinan Glacier in Iowa form the Des Moines Lobe landforms region. Much of Iowa was carved out by the Wisconsinan Glacier, which created the Des Moines Lobe 12,000-14,000 years ago. Most of northern and central Iowa show the landscapes that were created by this glacier, such as the central plains. The Des Moines Lobe advanced through North Dakota, South Dakota, Minnesota, and stopped where Des Moines, Iowa is today. As the glacier retreated, it carved the present course of the Raccoon River. An in-depth explanation or the Wisconsinan Glacier and the history of how it moved and created the landscape we see around us can be found here.
Northwest Iowa Plains
Another landform region in Iowa is the Northwest Iowa Plains. This region is located in the northwest corner of Iowa, and was created about 20,000-30,000 years ago. This region contains glacial deposits from both the Pre-Illinoian and Wisconsinan glacial advances. The Northwest Iowa Plains region also contributes to the diversity of the landscape in Buena Vista County.
Southern Iowa Drift Plain
The Southern Iowa Drift Plain is the largest of the landform regions and is located in the southern part of Iowa. This area is composed of glacial drift (gravel, sand, or clay that is picked up and deposited by the glacier as it moves) and was formed by Pre-Illinoian glaciers around 300,000 years ago. Much of the landscape has been changed over time. Today, much of the landscape has been cut away by rivers and there are prominent hills and valleys throughout the region.
Another landform region in Iowa is the Iowan Surface. It is covers a large portion of northeast Iowa and was created during Wisconsinan glaciation events 16,500-21,000 years ago. The landscape of the Iowan Surface includes gently rolling hills that are stark in contrast to the steep hills and valleys of the Southern Iowa Drift Plain.
The Loess Hills is another landform region of Iowa. This region is located in the western part of Iowa, extending from Sioux City, Iowa to St. Joseph, Missouri and was created about 18,000 years ago. The Loess Hills is a unique region to Iowa because of the tan, gritty sediment known as loess. Loess is a wind-deposited silt which is lightweight, porous, and can be easily eroded. The Loess Hills region is easily recognizable because of the way the loess forms in the “cat-step” ledges along the sides of the hills.
The most distinct of the landform regions is the Paleozoic Plateau which is located in the northeast corner of Iowa. This region is recognizable to visitors because of the rock outcroppings and ledges, very little glacial deposits, deep narrow valleys, cool-water streams, and heavily wooded uplands. The rock formations in this region contain layers as young as 300 million years and as old as 550 million years old.
The Alluvial Plains, sometimes called floodplains, were formed by water flowing off the landscape and carrying boulders, stones, gravel, sand, etc. This region is located along the Mississippi River and Missouri River lowlands. The Alluvial Plains serve as drainage networks that help transfer water and sediment into the Gulf of Mexico.