The Oldest Rock in the U.S., Dating Billions of Years Has Been Discovered in Michigan

The Earth has been around for a long, long time. For billions of years, this planet has been evolving and changing, and has gone through many devastating impacts from the solar system.

With this evolution, you can go to certain spots, even here in Michigan, and see the impact that those chaotic times caused in our rocks and cliff sides. Geologists are doing constant work to try to identify the history of our Earth in stones, and recently, there was an incredible discovery made in Michigan.

The discovery was so big that it’s changing the way that Geologists are now looking at these new discoveries, and pondering if we can find older ones. They have recently discovered the oldest rock in the United States in Michigan.

The rock is called Watersmeet Gneiss and was taken as a sample in the Upper Peninsula, and it contains zircons dating back to 3.82 billion years ago. That is a monumental discovery, considering this is the first time intact rocks dating back this far have been discovered.

Wyoming actually has Zircon fragments that date back 4 billion years, but they haven’t found intact rocks containing that as of this date. But how did the geologist make this discovery and determine the age? El Adelantado explains:

How were geologists even able to date these ancient rock formations?

The key lies in something smaller than a grain of sand, but tougher than your inherited cast-iron skillet: zircon crystals. When magma cools and forms rocks, zircon crystals lock in tiny amounts of uranium. Over billions of years, that uranium turns into lead at a predictable pace. By measuring the ratio of uranium to lead, scientists can tell how old the zircon is.