Large boulders stand alone in fields or along the roadways throughout northeast Iowa. The massive rocks transported to the area by giant floods and glaciers are called “erratics” because they are not derived from the underlying bedrock, which is typically limestone, shale and sandstone. Erratic boulders are widespread and many, but not all, of them are granitic in composition. Over time, erratics small enough to move are often collected and piled along fencerows and in the unused portions of cultivated fields.
Since 2009, Upper Iowa University (UIU) students have been working primarily in Fayette County on class and individual research projects related to these giant boulders. They constructed a database that details boulders greater than one cubic yard in volume, as well as some fieldstone accumulations. Known as the UIU Iowan Surface Erratics Research Group, participating students welcome the assistance of local farmers, land owners and historians in creating a more complete picture of the distribution and composition of the boulders and stony deposits in northeast Iowa and southeast Minnesota.
“Curiosity about these giant boulders goes back to the very first Iowans and the earliest geologists who worked in this area,” UIU Professor of Geosciences Dr. Katherine McCarville said. “The goal of the research project is to develop a better understanding of the Iowan Surface Landform Region. There are a number of features of the area that are not well explained by previous hypotheses for how it formed, so we are working on some new ideas. During their research the students also learn and develop skills in working on real-world problems.”
This spring, UIU’s earth systems science lab and geomorphology classes continue to work on the project. McCarville explained that by studying the locations and composition of large boulders and piles of fieldstone, and combining that information with maps of topography, geomorphological features, sediments and soils, the conditions under which the boulders and gravelly deposits accumulated may be determined.
“Many individuals have already contacted us, primarily within Fayette County, and we thank them for their assistance in our research,” McCarville said. “But now we need to expand the study area to include much of northeast Iowa and adjacent parts of Minnesota.”
By April 1, the project team would like to locate as many erratic boulders or accumulations of fieldstone and coarse gravel as possible within the project area. For some locations, it would be desirable for the students to gain permission from landowners to visit the location to measure size and determine composition of the boulders. However, McCarville noted that stories or photographs of large boulders that have been broken up, moved or have been buried, also provide information that is of value for the research.
Persons who know of boulders or piles of field stone, whether they are in their original locations or not, in northeast Iowa or southeast Minnesota are asked to contact McCarville at email@example.com or 563-425-5233.