Geology Home Page physical geology historical geology planetary gems
Roger Weller, geology instructor
by Ryan Fitzpatrick
Glacial Features of Iowa
When you think of the state Iowa, most people think of a state that is cover
with fields of corn and soybean. The reason why the state has such good soil to
grow such large amounts of corn and soybeans is because of the geology of the
state. The state is a highly glaciated landscape. The region of the upper
Midwest went through four periods of glaciation, they are in order of oldest to
youngest, Nebraskan period, Kansasan period, the Illinoian period and the
Wisconsinan period. The Nebraskan period and the Kansasan period are so old
they are hard to distinguish the differences so they call the formations in
these zones part of the Pre-Illinoian period as can be seen in Figure 1.
Areas of Glaciations in upper mid west United States.
Within the state of Iowa you can easily the area in which the glacier was on this area is the Des Moines lobe. The areas of the Iowan Surface, the Southern Iowa Drift Plain and the Northwest Iowa Plain are area of glacial outwash (Figure 2). The land form known as the Paleozoic Plateau is an area that was not affected by any of the glaciated periods and is mostly an area with a lot of exposed bed rock. The area is famous for effigy mounds and the Ice caves in the town of Decorah, Iowa (Figure 2).
Landform Regions of Iowa
As we know glaciers advance and retreat, with the Des Moines we are able to see
these advances such as the Bemis advance, the Renwick advance, the Algona
advance and the Altamont advance. We are able to see these advances within the
landscape with the formation of hilly areas known as moraines (Figure 3). The
most well known moraine know to Iowans is the most southern point of the Bemis
Moraine because this is the point in which the state capitol building is on
(Figure 4). Most of the moraines and advances are named for towns that lye on
Figure 3: Advances of the Des Moines Lobe
Figure 4: Iowa State Capitol Building in Des Moines, Iowa.
Glaciers, as we know, move and pick rocks and soils if it pick up those thing it
has to put them. The formations that we can see with in a landscape that come
from the glacier depositing soil are Kames and Eskers. An esker is a sand bar
that was within the glacier and was deposited when the glacier was done melting,
an example of an esker can be seen below in figure 5. The other feature that is
propionate is called a kame. A kame is where a glacier deposits all of the
soil, rocks and tilt in a mound formation, and example of a kame is the
Ocheyedan Mound in the town of Ocheyedan (figure 6). Kames are part of a
landscape known as a knob and kettle landscape. The kames are the knobs and
locations in which large chunks or ice stood after the glacier melted form
indents in the landscape we call these kettles since they are like large pots.
An example of a Kettle is the Freda Haffner Kettlehole (figure 7) in Dickenson
County. Dickenson County is a county that also has glacial lakes which is
visible by the presence Spirit and Okoboji lake systems.
Figure 5: Example of esker.
Figure 6: Ocheyedan Mound
Freda Haffner Kettlehole
Iowa’s glacier has hidden a great impact feature known as the Manson impact
crater. You are unable to tell at the surface there is a crater there the way
it was found to be a crater is by an analyst of the watershed. The loess hills
of western Iowa are known as the second deepest in the world, comparable to
those in china. Loess is a wind derived soil found on the opposite side of a
river valley that the winds come in. The loess in western Iowa was blown on top
of the glacier and then was deposited top on the glacial tilt as the ice melted.
Map of Loess Thickness in the mid west.
Figure 9: Profile of Loess
Diagram how loess was deposited in Western Iowa.
features pointed out are the largest and most noticeable features because or
effected by glacial geology. If you have the time go and explore and find the
smaller features that affect your everyday life.
Burras, Dr. Lee. Lectures and notes from Iowa State University courses EnSci 473I, EnSci 402 and Agron 260. 2004-2006. Ames, IA.
Figure 1. Iowa DNR. www.igsb.uiowa.edu/Browse/glatrail/glatrail.htm
Figure 2. Iowa DNR. http://www.igsb.uiowa.edu/Browse/geoiowa/GEOIOWA.HTM .
Figure 3. Iowa DNR. www.igsb.uiowa.edu/Browse/glatrail/glatrail.htm
Figure 4. Wikipedia. http://en.wikipedia.org/wiki/State_legislature_(United_States)
Figure 5. Iowa State University Geographic Information Systems Support and Research Facility. http://ortho.gis.iastate.edu
Figure 6. Iowa DNR. www.igsb.uiowa.edu/Browse/glatrail/glatrail.htm
Figure 7. Iowa DNR. www.igsb.uiowa.edu/Browse/glatrail/glatrail.htm
Figure 8. USGS. Ritter, Michael E. The Physical Environment: an Introduction to Physical Geography.2006. 11-11-07. www.uwsp.edu/.../eolian_systems/loess.html
Figure 9. Harrison County Conservation Board website. www.harrisoncountyparks.org/loesshills.htm
Figure 10. USGS. http://pubs.usgs.gov/info/loess/
I have my B.S. in Environmental Science from Iowa State University in Ames, IA.