In this episode, we dive back into the bedrock of America to reveal which state holds the crown for the oldest rocks in the U.S.! Join us as we unravel the mysteries of ancient metamorphic formations. From the Morton Gneisses in Minnesota, to the Wyoming craton out West, and ending in Upper Michigan, you'll find out what the oldest rocks are, and how we know! Hit that subscribe button, because this episode rocks!

The paper that served as the basis for this episode is Frost, C.D., Mueller, P.A., Bickford, M.E., and Stern, R.J., 2025, USA’s oldest rock? A simple question with a complex answer: GSA Today, v. 35, p. 4–10,
https://doi.org/10.1130/GSATG613A.1.

00:00 Introduction and Episode Overview

00:50 Setting the Stage: America's Oldest Rocks

02:28 Understanding Metamorphic Rocks

05:18 The Importance of Rock Ages

09:55 Zircon and Uranium-Lead Dating

14:16 Metamorphism and Zircon Growth

22:05 Metamorphic and Igneous Rock Processes

23:32 Understanding Zircon Inheritance

24:32 Determining Rock Ages

27:21 Challenges in Identifying Rock Types

31:44 Oldest Rocks in the United States

36:52 Technological Advancements in Geochronology

42:51 Conclusion and Further Research

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Join us as we explore the towering history of ancient mountain ranges, delve into the mysteries of the Appalachian Mountains, and break down the geological story behind the Gettysburg region. From the immense rift basins on the East Coast to the intricate details of the Allegheny Orogeny, this episode promises a thrilling ride through Earth's dynamic layers. Get ready to rock with some punny sediment tales and discover how past geological events shaped the terrain we see today! The Birdsboro basin may represent the larger Mesozoic rift basin that we only get small glimpses of today!

Download the CampGeo app now at this link.

On the app you can get tons of free content, exclusive images, and access to our Geology of National Parks series.
You can also learn the basics of geology at the college level in our FREE CampGeo content series - get learning now!

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What is the oldest rock you can stand on in the United States? As the title of Frost et al., 2025 says, it is a simple question with a complex answer. In this episode, we journey to the north-central United States, where you'll find some of the oldest rocks in North America. Join us as we go through the candidate locations and dive real deep into the weeds of zircon uranium-lead geochronology! The more you learn, the less you know.

Download the CampGeo app now at this link.

On the app you can get tons of free content, exclusive images, and access to our Geology of National Parks series.
You can also learn the basics of geology at the college level in our FREE CampGeo content series - get learning now!

Like, Subscribe, and leave us a Rating!

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Instagram: @planetgeocast
Twitter: @planetgeocast
Facebook: @planetgeocast
Support us: https://planetgeocast.com/support-us
Email: planetgeocast@gmail.com
Website: https://planetgeocast.com/