Gitchie Manitou State Preserve and Sioux Quartzite

Shown are the Gitchie Manitou State Preserve and its Sioux Quartzite outcroppings. These outcropping represent the oldest visible exposed bedrock in Iowa, going back nearly 1.6 billion years ago. 

• What makes this area of Iowa unique?

• How can the rocks be so old?
• How do we know the rocks are so old?

Students could:

• Compare the Sioux Quartzite to other rocks in Iowa and around the world.
• Work in groups to research how rocks are dated using different techniques (radioactivity and stratigraphy).
• Analyze data of rock ages in Iowa and around the world, while noting where rocks of different ages can be found relative to plate boundaries and mid-ocean ridges.
• Analyze rock sample of different ages from around the state.
• Identify patterns where rocks of different ages can be found.

• GeoScience World | Precambrian Sioux Quartzite at Gitchie Manitou State Preserve, Iowa: Teacher background information on Gitchie Manitou and its Sioux Quartzite features. Click on “Chapter PDF” to access a readable version.
• PBS LearningMedia | Iowa Land and Sky : The Geology of Iowa's Gitchie Manitou State Preserve: Student-friendly reading and discussion questions on Gitchie Manitou.
• Utah Geological Survey | How Do Geologists Know How Old a Rock Is?: Student-appropriate article on relative and absolute dating of rocks.
• University of Iowa IIHR Iowa Geological Survey (GIS) | Interactive Maps: Includes various maps of Iowa geology, including county-level maps of rock formations.
• National Oceanic and Atmospheric Administration (NOAA) | Age of Oceanic Lithosphere: Map of the age of Earth’s oceanic crust.
• Earth Magazine | When and How Did Plate Tectonics Begin on Earth?: Includes a map of the age of Earth’s continental crust.