Rocky Road Trip

In 2024, over 70% of Americans road tripped, with 50% saying they want the opportunity to detour to see their country’s landscapes.1 The US is a playground of natural wonders: Niagara Falls, the Everglades, Yellowstone, Yosemite, the Grand Canyon. But most of these glorious sights wouldn’t exist without the catastrophic flood of Noah’s day.

In the flood judgment, God destroyed the earth with waters that “prevailed so mightily on the earth that all the high mountains under the whole heaven were covered” (Genesis 6:7–13, 7:19–21). With a devastation of this magnitude, we would expect to see evidence around the globe.

And we do, of course, in the billions of marine fossils in water-deposited sediment layers across every continent.

But another record is present on every continent, and it spans the United States from California to New York—an erosion scar marking the flood’s onset, called the Great Unconformity.

The Global Erosion Scar

An unconformity is an erosion surface that marks the boundary between two sets of rock layers that do not conform to one another. That is, they are aligned at different angles to one another. In evolutionary terms, the rocks directly above the Great Unconformity are called Cambrian, and those below are called Precambrian.

One Scar. Different Elevations.

When the flood waters swept across the North American continent, the Precambrian layers below the unconformity were significantly affected by an upheaval that distorted them. The resulting erosion scar would have been at a similar topographic level across the would-be US. In some places, more than 10,000 feet (3048 m) of layers were eroded away to expose the Great Unconformity.

As the flood waters rose, they rapidly deposited fossil-bearing sediments in layers on top of the Great Unconformity. (The Precambrian layers beneath it have few fossils, distinguishing them as original, pre-flood rock layers.)

You might expect this erosion scar to still be at the same elevation, but the Great Unconformity is found at different elevations in different locations across the US—at roughly 1,277 feet (389 m) above sea level beneath northern Illinois and at the bottom of the Grand Canyon in northern Arizona, but at more than 12,600 feet (3840 m) above sea level on Mt. Moran in the Grand Tetons, Wyoming.

Why the difference? At the end of the flood and for the next few decades, the mountains rose, and the valleys sank as the waters drained off the continents into today’s ocean basins (Psalm 104:7–9). Across the US, the Rockies and Sierra Nevada rose to great heights; and across the Midwest, the continent rose to various elevations along dramatic fault lines.

While the Great Unconformity stands at roughly 12,600 feet (3840 m) above sea level on Mount Moran in the Grand Tetons, it also sits more than 20,000 feet (6096 m) beneath nearby Jackson Lake.

Learning from Scars

Scars are evidences of past trauma, and the Great Unconformity is no different. It is found at the same geological level on every continent, earning the name the Great Unconformity because it is so universal, just like the flood. Its scar reminds us that our holy God hates sin and must judge it.

Yet it also tells of God’s grace. As the earth continued to shift and change in the post-flood upheaval, its scars gave way to beauty. We have the flood catastrophe to thank for America’s purple mountain majesties that prompted the songwriter to pen, “God shed his grace on thee.”

Even with its scars, the earth is “full of his glory” (Isaiah 6:3)—glories you can enjoy on your family road trips.

Mapping Your Roadtrip

Most people cannot hike to the bottom of the Grand Canyon or to the top of Mt. Moran to see the Great Unconformity up close. But here are five locations that you can access on your next road trip across the US.

1. Grand Canyon, Arizona
While you may not find the deep gorges of the Grand Canyon accessible, you can see the Great Unconformity from the rim overlooks.

2. Colorado Springs, Colorado
You can glimpse the Great Unconformity in several locations near Colorado Springs. To the southwest, along the road to Manitou Springs, it’s visible in a road cut. North of Garden of the Gods, you can see it clearly in the cliffs above the creek that runs along the northeastern side of a parking lot behind Glen Eyrie, the headquarters of the Navigators.

3. US 67, Eastern Missouri
Due south of St. Louis, along US 67, between Farmington and Fredericktown, is a road cut where you can see the Great Unconformity.

4. Chippewa Falls, Wisconsin
Just north of Eau Claire in Chippewa Falls, you can see the Great Unconformity from a trail through wild undergrowth on the eastern bank of the creek upstream in a large public park.

5. Wind River Canyon, Wyoming
On a US 20 road cut within the Wind River Canyon of central Wyoming, you can find the Great Unconformity.