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General Geology

Mineral, Rock, and Fossil Identification

Geologists at the Iowa Geological Survey regularly identify rocks, minerals, and fossils that are brought into our office.  If you are not able to stop by our office, send photos of the specimen via email.  Please make sure that the photos capture all aspects of the specimen, are in focus, and include a common object for scale (i.e. ruler, quarter, pen, etc.).  Include a brief description of where the specimen was found in the email.  Specimens can also be mailed to the IGS for identification, and returned if requested.

For more information contact Ryan Clark.

Rock Units

One of the primary duties of the Iowa Geological Survey is to continuously work to increase our understanding of the rock units (or stratigraphy) in Iowa.  Knowledge of each rock unit, its aerial extent, its physical and chemical characteristics, and how it interacts with other units is critical to address groundwater needs, mineral resources, pollution problems, and almost every other aspect of geology in Iowa.  Almost 450 rock units were deposited in the area that is now Iowa in the last 3 billion years.  The oldest known unit is the Otter Creek Mafic Complex (about 2.95 billion years old), the youngest is the Wisconsin-age glacial drift of the Des Moines Lobe (about 10,000 years old).  Additionally, we work with river sediments that are still being deposited today.

The Stratigraphic Column of Iowa and its nomenclature are available.

For more information contact Ryan Clark.

Landform Features

Iowa’s landscape varies widely in appearance from place to place across the state.  Individual landform shapes reflect the diverse effects of deposits left by glaciers, wind, rivers, and seas during the geologic past.  Examples include loess hills, moraines, kettles, kames, pahas, sinkholes, caves, springs, algific slopes, oxbow lakes, and entrenched valleys.

For more information contact Stephanie Surine.

Glacial-Age Deposits

Materials from several different glacial advances cover different parts of Iowa and bury most of the sedimentary bedrock foundation from view.  Other earth materials near the land surface also accumulated during glacial episodes, including loess (deposits of wind-blown silt) and alluvium (sand and gravel transported by glacial meltwater streams).

For more information contact Stephanie Surine.

Geographic and Locational Information

The determination of the location of particular features or of distributions of phenomena on the earth’s surface and subsurface is a necessary part of geology, and methods developed to find and record locations have become an important tool for all earth scientists.  Locational relationships between two phenomena, whether they are close together or thousands of miles apart, may be relevant to an understanding of how they fit within the whole earth system.  Geologists at the Iowa Geological Survey use a variety of spatial tools, including remote sensing technology, geographic information systems (GIS), U.S.G.S. topographic maps, and aerial photography.

The NRGIS library provides many GIS coverages of Iowa.

For more information contact Casey Kohrt.

Earth History

Developing an integral understanding of Earth history is basic to a complete knowledge of Iowa geology.  Iowa’s rocks record a geologic history that goes back almost 3 billion years. Geologists at the Iowa Geological Survey strive to keep up to date with the latest advances in most aspects of Earth history.  They can answer questions on the age, depositional histories, climatic conditions, and other aspects of the formation of the geologic units in Iowa.  The stratigraphic column of Iowa lists all of the geologic units in Iowa by age.

For more information contact Ryan Clark.

Natural Resource and Environmental Issues

Geologists are frequently asked for information needed to resolve environmental issues in today’s society.  Iowa’s earth-related issues include land-applied agricultural chemicals, areas where groundwater supplies are vulnerable to contamination, areas of shallow limestone (karst conditions), mineral resource reserves, adequate groundwater supplies, and disposal of waste materials.  Some current topics of statewide concerns include, but are not limited to the increase in large hog-confinement operations and how the animal wastes are stored, mining of bedrock sandstone units for the petroleum industry, and over-use of the Jordan aquifer.


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Last modified on July 6th, 2017
Posted on April 30th, 2014