Two separate research reports arrived at a similar conclusion.^1,2 Both found an episode of mysterious erosion had occurred near the end of the Tejas Megasequence. This event likely correlates to the final phase of water draining off the continents during the Flood. It also confirms a late Cenozoic end of the Flood boundary, called the N-Q (Neogene-Quaternary).^3,4

The upper subdivisions of the geologic column with the N-Q and the K-Pg boundaries identified

The study team led by Natalie Tanski, who’s now at the University of Oklahoma, discovered that river incision paused in the early to middle Pleistocene (Ice Age) and was followed by a brief period of rapid incision in the late Pleistocene to the present. They speculated that this hiatus in erosion “may record a planated [smoothed at one elevation] landscape prior to the propagation of baselevel fall from Colorado River integration.”¹

They further noted that this recent river incision only accounts for about 200 meters (650 feet) of the total erosion off the central Colorado Plateau. The team concluded, “This requires an unknown driver of significant ~ Pliocene exhumation [erosion] of the central Colorado Plateau that is not linked to Colorado River integration [later stream development by incision].”¹ They added, “The driver for the older, Pliocene erosion [~2 km or 1.25 mi] of the landscape recorded by thermochronology, and where that eroded mass went, present enduring problems.”¹ Tanski et al. also wrote, “Therefore, the majority of the total exhumation in Late Cenozoic [Pliocene] must have occurred before the Colorado River responded [upstream] to integration, and it requires a different source of base level fall.”¹

What could have caused the removal of 1.25 miles of sedimentary cover in the Moab, Utah, area and the removal of over 0.62 miles of sediment at Glen Canyon, resulting in the broad planation (leveling) of the land surface? This massive Pliocene erosion event has been a long-enduring problem for conventional geologists, going back to the work of geologist Clarence Dutton in 1882, who labeled this mysterious erosion the Great Denudation.⁵

What caused the Great Denudation that ended in the Pliocene? And what might have caused the hiatus in erosion at the end of the Pliocene and during the earliest part of the Ice Age (early and mid-Pleistocene)? Before we suggest answers for these questions, let’s examine the results of the second study.

Emmanuel Gabet of San Jose University examined the canyons of the central Sierra Nevada Mountains, including Yosemite Valley.² He determined the present rivers are too small to have carved the massive and deep canyons in the central Sierra Nevadas, so he postulated that there must have been a lot more water flowing through these canyons in the past, particularly prior to the Ice Age, in the Miocene and Pliocene.² But there is little evidence of this massive river today.

His interpretation of this supposed missing river system is supported by thick and extensive volcanic-rich sediments found in the Central Valley.² He suggested these volcanic rocks were transported by the missing river. And yet, there are no volcanoes in the central Sierra Nevadas to supply the volcanic sediment. Gabet told Live Science, “You’ve got 8 cubic miles [33.3 cubic kilometers] of volcanic sediment deposited in the Central Valley by the Merced River, but you can’t find a scrap of these volcanic [source] rocks in the area around the river.”⁶

Gabet did locate Miocene and Pliocene (late Tejas) volcanoes in the northern Sierra Nevadas that could have been the source of these sediments. But that would have required long-distance transport by water, hence his proposal of a massive, missing “ghost” river to transport these volcanic sediments.⁶ All of this water transport and erosion occurred just prior to the Ice Age (Pleistocene). Later, alpine glaciers during the Ice Age scoured and widened these earlier-formed valleys, producing the Yosemite Valley we see today.

Because conventional geologists deny the historical accuracy of Genesis, they operate at a loss. They see evidence of massive erosion and tremendous water flow at the end of the Tejas Megasequence and just prior to the Ice Age but are hampered by their uniformitarian thinking to explain it.

But the Bible gives us answers. Genesis describes a global flood that peaked on Day 150.³ The sedimentary rocks across all of the continents confirm this peak occurred at the end of the Zuni Megasequence (at the K-Pg).³ And the rocks confirm that the Tejas Megasequence records the subsequent receding phase.^3,7–10

The massive water erosion that took place in the late Tejas (Miocene and Pliocene) in these two studies is best explained by the receding phase of the Flood. There is no mystery to this erosion. As the floodwater rapidly drained off the continents, we would expect massive removal off the top of the underlying sediments. This unfathomable volume of water draining off the land could have easily transported volcanic material from the northern Sierra Nevadas to the central Sierras. And it could have provided sufficient water to carve massive canyons, like Yosemite Valley.

Likewise, the erosive power of the receding floodwater is the best explanation for the Great Denudation in the central Colorado Plateau. How else could over a mile of sediment disappear from southeastern Utah and the surrounding regions, beveling the surface nearly flat? It also explains the mysterious hiatus in erosion at the end of the Pliocene. Erosion likely ceased after the floodwaters had finished draining off the continents, resulting in a pause in erosion marked by the upper Flood boundary at the N-Q (just prior to the Ice Age).⁸

The renewed river incision that occurred late in the Ice Age and after was minimal compared to the erosion caused by Miocene and Pliocene flood runoff. And this river incision could have been enhanced by the heavier precipitation in these regions during the Ice Age and increased flow as the ice melted away.³

There is no mystery when the Bible is accepted as truth. Geology only makes sense if viewed within a biblical worldview that accepts the reality of the global Flood.

References

1. Tanski, N. M. et al. 2025. The Mystery of Baselevel Controls in the Incision History of the Central Colorado Plateau. AGU Advances. 6 (1): e2024AV001359.
2. Gabet, E. J. 2025. Is Drainage a Plausible Explanation for Late Cenozoic Incision of Yosemite Valley and within Kings and Kaweah Watershed (Sierra Nevada, California)? Geosphere. 21 (3): 332–351.
3. Clarey, T. 2020. Carved in Stone: Geological Evidence of the Worldwide Flood. Dallas, TX: Institute for Creation Research.
4. The Tejas Megasequence is the last of six major “chapters” comprising the global Flood. Five show a progressive flooding of every continent, peaking at the K-Pg (Cretaceaous-Paleogene) near the top of the fifth (Zuni) megasequence. And the last one, the Tejas, encompassed the receding phase of the Flood when water was draining off the continents. The Tejas coincides with the old Tertiary System, now called the Paleogene and Neogene with the Neogene on top. The Neogene includes the Miocene and Pliocene deposits—the last of the Flood sediments prior to the Ice Age, respectively.
5. Dutton, C. E. 1882. Tertiary History of the Grand Cañon District, vol. 2. Washington, D.C.: U.S. Government Printing Office.
6. Pappas, S. Yosemite’s Ultra-Deep Canyon May Have Been Carved in Part by a Ghost Volcano and River, Provocative Research Suggests. Live Science. Posted on livescience.com May 12, 2025, accessed June 15, 2025.
7. Clarey, T. L. and D. J. Werner. 2019. Compelling Evidence for an Upper Cenozoic Flood/Post-Flood Boundary: Paleogene and Neogene Marine Strata that Completely Surround Turkey. Creation Research Society Quarterly. 56 (2): 68–75.
8. Tomkins, J. P. 2023. The Receding Phase of the Genesis Flood: Exegetical and Geological Notes on Genesis 8:1-12. Creation Research Society Quarterly. 59 (4): 207–216.
9. Tomkins, J. P. and T. Clarey. 2022. Paleontology Supports an N-Q Flood Boundary. Acts & Facts. 51 (2): 7.
10. Clarey, T. 2019. Rocks Reveal the End of the Flood. Acts & Facts. 48 (5): 9.

* *Dr. Clarey is the director of research at the Institute for Creation Research and earned his doctorate in geology from Western Michigan University.