Rosa Rubicondior: Creationism Refuted - How The Grand Canyon Was Formed

Lost mega-escarpment across ancient USA may explain Grand Canyon missing billion years

Creationists sometimes point to the Great Unconformity in the Grand Canyon as evidence of Noah’s mythical global flood. But an unconformity is not a layer deposited by a flood. It is a surface representing an interval during which older rocks were exposed, eroded and sometimes deformed before younger sediments were laid on top of them. What is “missing” is not evidence; it is rock that either was never deposited or was subsequently removed, with the surviving rocks preserving evidence of what happened in the intervening time.

Creationists attempts to fit the Grand Canyon into their Biblical flood myth range from the sublime to the ridiculous, none of them in the least plausible and designed to appeal to the parochial ignorance that typifies American creationism. Their conclusion is always sacred and immune to contradiction. Facts are accepted or rejected based on whether they support the conclusion or not. Science, by contrast, starts with a neutral view, collects evidence, then takes a view that accounts for that evidence, as always in science, the facts are neutral and the conclusion provisional, contingent on the discovery of more evidence.

At parts of the Grand Canyon, Cambrian sedimentary rocks rest upon much older Precambrian rocks, leaving more than a billion years of geological history unrepresented by sedimentary strata at that particular location. Far from supporting the idea that the canyon’s rocks were deposited during a single year-long catastrophe, the contact records a succession of events involving sedimentation, burial, tectonic disturbance, uplift, prolonged exposure, erosion and renewed deposition.

A new study published open access in the journal Geology now proposes a mechanism that may explain much of the extraordinary erosion responsible for this gap in the south-western United States. Thomas M. Gernon of the University of Southampton and colleagues have reconstructed a continent-scale escarpment that may have developed along the western margin of Laurentia—the ancient continental core of North America—as the supercontinent Rodinia began breaking apart approximately 800–750 million years ago.

The proposed “Great Escarpment of Laurentia” would have resembled, on a much larger scale, the great rift-margin escarpments found today in southern Africa and Brazil. Continental rifting produced uplifted ground and steep slopes along the new margin. As rivers, weathering and possibly glaciers attacked this terrain, the escarpment gradually retreated inland over tens of millions of years, progressively exposing rocks that had formerly been buried deep within the continental crust.

The researchers combined plate-tectonic reconstructions with computer models of long-term landscape evolution. Their reconstruction places the future Grand Canyon region within the range of distances from the continental margin occupied by comparable younger escarpments. The models predict erosion reaching approximately eight kilometres near parts of the escarpment, declining to about one or two kilometres farther away. This is consistent with independent geological evidence that some five to ten kilometres of rock were removed from parts of the region long before the modern Grand Canyon was carved.

The distinction is important. The study is not claiming that this ancient escarpment was the Grand Canyon, nor that the Colorado River existed 800 million years ago. Rather, it proposes that the breakup of Rodinia helped exhume the ancient crystalline basement which the much younger Colorado River eventually cut through. The familiar canyon landscape is merely the latest episode in a history extending back almost two billion years.

Nor should the study be presented as a final, universal explanation for every occurrence of the Great Unconformity. Its extent, duration and amount of missing rock vary greatly from place to place, and geologists have investigated contributions from several episodes of tectonic uplift and erosion, including Cryogenian glaciation. Gernon and colleagues offer a testable explanation for why erosion was especially deep and spatially variable across the south-western United States—not a single cause imposed upon every unconformity worldwide.

Two Accounts of the Grand Canyon. Young-Earth creationists present the Grand Canyon as evidence of Noah’s Flood, whereas geologists regard it as the visible result of many separate events extending across almost two billion years. These are not merely two interpretations of the same evidence. The creationist account begins with the required truth of Genesis and compresses the evidence into that story; geology reconstructs the sequence from the rocks themselves.

Question Typical creationist claim Geological explanation

How old are the rocks? The canyon’s sedimentary rocks were deposited only a few thousand years ago, mostly during Noah’s year-long global Flood. Radiometric ages are rejected because they conflict with the assumed biblical chronology. The exposed rocks have independently measured ages ranging from almost 1.84 billion years for parts of the crystalline basement to about 270 million years for the youngest strata preserved at the canyon rim. Their minerals, fossils, magnetic signatures and relationships with adjoining rocks agree with this chronology.

How were the strata deposited? Most of the horizontal sedimentary layers were laid down rapidly by successive stages of a single catastrophic flood. The formations preserve evidence of numerous environments at different times, including shallow seas, coastal plains, rivers, tidal flats and deserts. Fossil burrows, footprints, dune cross-bedding, mud cracks and erosion surfaces record intervals during which organisms lived, sediment dried, landscapes were exposed and erosion occurred before further strata accumulated.

What is the Great Unconformity? It is sometimes presented as a surface scoured by the onset of Noah’s Flood, upon which later “Flood rocks” were rapidly deposited. It is an erosional boundary representing long intervals for which rock is absent. In different parts of the canyon, Cambrian strata overlie either tilted rocks of the Grand Canyon Supergroup or much older crystalline basement. The differing contacts and amounts of missing time show that this is not one globally synchronous flood-scoured surface.

What removed so much older rock? Vast quantities of water associated with the biblical Flood are invoked, usually without a quantitative tectonic or landscape model. Several episodes probably contributed. These include mountain building, uplift, continental rifting during the break-up of Rodinia, weathering, river erosion and possibly Cryogenian glaciation. The newly proposed Great Escarpment of Laurentia could have concentrated erosion in the south-western United States over tens or hundreds of millions of years.

How was the canyon carved? Creationists variously attribute it to rapidly retreating Flood water or to the sudden breaching of one or more enormous post-Flood lakes. There is no single agreed creationist mechanism. Uplift of the Colorado Plateau steepened river gradients, while integration of the upper and lower Colorado drainage systems gave the river an outlet towards the Gulf of California. The through-flowing river began cutting the modern canyon approximately five to six million years ago, assisted by tributaries, weathering, landslides and repeated high-discharge events.

Was erosion always slow? Examples of rapid erosion are offered as proof that the whole canyon could have formed almost instantaneously. Geologists do not assume that erosion always proceeds at a constant, imperceptibly slow rate. Floods, debris flows, rockfalls and volcanic dam failures can cause rapid local change. Such events operated repeatedly within a landscape whose overall development is constrained by millions of years of dated lava flows, river gravels, sediments and cooling histories.

The essential distinction: the rocks, the unconformities and the canyon are not the same age. Ancient rocks were formed, buried, deformed, uplifted and eroded long before the modern Colorado River cut through them. The canyon exposes that history; it did not create it.

Scientific uncertainties remain, particularly over the earlier drainage systems and the relative contributions of tectonics, rivers and glaciers to ancient erosion. These are disagreements about details within an evidence-based chronology—not support for replacing almost two billion years of geological history with an unevidenced supernatural flood.

Question	Typical creationist claim	Geological explanation
How old are the rocks?	The canyon’s sedimentary rocks were deposited only a few thousand years ago, mostly during Noah’s year-long global Flood. Radiometric ages are rejected because they conflict with the assumed biblical chronology.	The exposed rocks have independently measured ages ranging from almost 1.84 billion years for parts of the crystalline basement to about 270 million years for the youngest strata preserved at the canyon rim. Their minerals, fossils, magnetic signatures and relationships with adjoining rocks agree with this chronology.
How were the strata deposited?	Most of the horizontal sedimentary layers were laid down rapidly by successive stages of a single catastrophic flood.	The formations preserve evidence of numerous environments at different times, including shallow seas, coastal plains, rivers, tidal flats and deserts. Fossil burrows, footprints, dune cross-bedding, mud cracks and erosion surfaces record intervals during which organisms lived, sediment dried, landscapes were exposed and erosion occurred before further strata accumulated.
What is the Great Unconformity?	It is sometimes presented as a surface scoured by the onset of Noah’s Flood, upon which later “Flood rocks” were rapidly deposited.	It is an erosional boundary representing long intervals for which rock is absent. In different parts of the canyon, Cambrian strata overlie either tilted rocks of the Grand Canyon Supergroup or much older crystalline basement. The differing contacts and amounts of missing time show that this is not one globally synchronous flood-scoured surface.
What removed so much older rock?	Vast quantities of water associated with the biblical Flood are invoked, usually without a quantitative tectonic or landscape model.	Several episodes probably contributed. These include mountain building, uplift, continental rifting during the break-up of Rodinia, weathering, river erosion and possibly Cryogenian glaciation. The newly proposed Great Escarpment of Laurentia could have concentrated erosion in the south-western United States over tens or hundreds of millions of years.
How was the canyon carved?	Creationists variously attribute it to rapidly retreating Flood water or to the sudden breaching of one or more enormous post-Flood lakes. There is no single agreed creationist mechanism.	Uplift of the Colorado Plateau steepened river gradients, while integration of the upper and lower Colorado drainage systems gave the river an outlet towards the Gulf of California. The through-flowing river began cutting the modern canyon approximately five to six million years ago, assisted by tributaries, weathering, landslides and repeated high-discharge events.
Was erosion always slow?	Examples of rapid erosion are offered as proof that the whole canyon could have formed almost instantaneously.	Geologists do not assume that erosion always proceeds at a constant, imperceptibly slow rate. Floods, debris flows, rockfalls and volcanic dam failures can cause rapid local change. Such events operated repeatedly within a landscape whose overall development is constrained by millions of years of dated lava flows, river gravels, sediments and cooling histories.

That caution illustrates the difference between science and creationism. Geologists compare plate reconstructions, thermochronological evidence, rock relationships and quantitative landscape models, then refine their explanations as new evidence becomes available. Creationists begin with a supernatural flood story and attempt to force every geological feature into it. Unfortunately for them, this particular surface records not one brief catastrophe but hundreds of millions of years of continental fragmentation, uplift and erosion.

The paper in Geology was accompanied by a University of Southampton news item.

Lost ‘mega-escarpment’ across ancient USA may explain Grand Canyon’s missing billion years
Scientists have found evidence that a colossal cliff stretching thousands of kilometres across ancient North America may have exposed the heart of the Grand Canyon nearly a billion years before it was carved by the Colorado River.

Grand Canyon’s oldest and deepest rocks were unearthed by massive cliff across ancient USA.

The study, led by the University of Southampton in the UK, proposes that a vast “great escarpment” of steep rocky cliffs formed when the supercontinent Rodinia broke apart 800 million years ago.

Experts suggest the kilometre-high cliffs extended along much of western North America, driving erosion of enormous volumes of rock and exposing ancient crystalline basement now visible in the Grand Canyon, southern Arizona.

Lead author Professor of Earth Science Thomas Gernon , from Southampton, said the Grand Canyon has a geological record spanning two billion years, but more than half of its rock record appears to be missing.

Our paper suggests the Canyon’s basement rocks were progressively brought to the surface as part of an immense escarpment that developed during the breakup of an ancient supercontinent. The findings also shed light on the formation of the Great Unconformity, a mysterious gap in the rock record that spans over a billion years.

Professor Thomas Gernon, lead author.
School of Ocean & Earth Science
University of Southampton
Southampton, UK.

The study, published in Geology, included experts from the University of Southampton, GFZ Helmholtz Centre for Geosciences and University of Potsdam, both in Germany, and the University of Illinois Urbana-Champaign in the USA.

According to their findings, the ancient great escarpment would have stretched across what are now Arizona, Utah, Idaho, Wyoming, Colorado, Texas, Oklahoma, Arkansas, Missouri and Illinois.

This is where intense erosion ultimately exposed some of North America’s oldest rocks, including most famously at the Grand Canyon, said Prof Gernon.

The researchers combined plate tectonic reconstructions with landscape evolution data to recreate how western North America evolved as Rodinia fragmented.

It showed the Grand Canyon occupied the same position relative to the ancient continental margin as many of today’s great escarpments in South Africa and Brazil.

As the escarpment slowly retreated inland over tens of millions of years, it is predicted to have stripped away up to eight kilometres of rock in places.

The findings are consistent with evidence that the region experienced extraordinary erosion of some five to ten kilometres of rock long before the modern canyon formed.

This long-lived tectonic landscape provides a missing piece in understanding why erosion associated with the Great Unconformity varies so dramatically across the southwestern US. Our work suggests that tectonic uplift related to continental rifting and breakup created both steep slopes and high ground, providing the mountainous terrain that rivers and glaciers could readily erode.

Professor Thomas Gernon.

The study also reveals the ancient escarpment may have influenced far more than the Grand Canyon itself.

By creating a long-lived mountainous rim around western Laurentia - the ancient core of North America - it may have controlled where rivers flowed, sediments accumulated, and when rising seas flooded the continent prior to the so-called Cambrian explosion, when complex life rapidly diversified.

Today’s escarpments in Africa, Brazil, India and Antarctica provide windows into the forces that shape continents over hundreds of millions of years. By comparing Grand Canyon’s ancient history with active landscapes like the Great Escarpment of South Africa, we’re able to see North America’s most iconic geologic landmark in an entirely new light.

Our findings could help geologists reinterpret other ancient continental interiors where similarly large gaps occur in records, offering a better understanding of how Earth’s continents have changed over hundreds of millions of years.

Professor Thomas Gernon.

Publication:
Thomas M. Gernon, Thea K. Hincks, Elias J. Rugen, Sascha Brune, Jean Braun, Stephen Marshak
Exhumation of Grand Canyon’s basement along the Great Escarpment of Laurentia.
Geology 2026; doi: https://doi.org/10.1130/G55133.1

Abstract
The Grand Canyon encompasses two billion years of Earth history, but more than half this record is absent across a regionally extensive erosional surface known as the Great Unconformity. This enigmatic surface has been linked to multi-phase regional tectonics accompanying supercontinent assembly and breakup and to Cryogenian glacial erosion. Although rift-related uplift during the breakup of Rodinia has long been implicated in erosion associated with the Great Unconformity, we argue that exhumation in the Grand Canyon region was focused along a continent-scale rift-flank escarpment. This “Great Escarpment of Laurentia,” initiated ca. 800−750 Ma, occupied a position analogous to major escarpments generated during Mesozoic Gondwana breakup and experienced similar magnitudes of exhumation. Our landscape evolution models simulating rift-driven topography suggest that rocks within several hundred kilometers of this feature endured substantial erosion, reaching 8 km near the escarpment and decreasing to ≤2 km at lateral distances of ∼200 km from its peak. Such differential erosion, evidenced in prior thermochronology models, necessitates exhumation of mid-crustal basement lithologies including along reactivated crustal fault blocks. This model helps explain the variable magnitude of erosion associated with the Great Unconformity in the southwestern United States.

Figure 1. (A) Reconstruction of Laurentia at Cryogenian glacial onset (717 Ma), based on the plate model of Merdith et al. (2019). The projected distribution of Ediacaran sedimentation after Segessenman and Peters (2025) suggests the existence of a topographic barrier during the Ediacaran. (B) Illustration of the Grand Canyon showing Great Unconformity surfaces, inferred temperatures of metamorphism, and depths of burial (by Gary Hincks, modified after Karlstrom et al., 2021). (C) Paleogeographic reconstruction of North America at 65 Ma (reproduced under license from deeptimemaps.com), showing the broad position of the ancestral escarpment (pre-Basin-and-Range extension). COB—continent-ocean boundary.

Thomas M. Gernon, Thea K. Hincks, Elias J. Rugen, Sascha Brune, Jean Braun, Stephen Marshak
Exhumation of Grand Canyon’s basement along the Great Escarpment of Laurentia.
Geology 2026; doi: https://doi.org/10.1130/G55133.1

Copyright: © 2026 The authors.
Published by Geological Society of America. Open access.
Reprinted under a Creative Commons Attribution 4.0 International license (CC BY 4.0)

The significance of this research is not that the Great Escarpment of Laurentia has now been established as the sole cause of the Great Unconformity. It is that the hypothesis connects a reconstructed episode of continental break-up with measurable patterns of uplift, erosion and basement-rock exhumation. Its predictions can be compared with thermochronological evidence, plate reconstructions and the geographical variation in the amount of missing rock. Like any scientific explanation, it remains open to refinement or rejection if the evidence fails to support it.

What it cannot reasonably be compressed into is a year-long global flood a few thousand years ago. The rocks exposed in the Grand Canyon record repeated episodes of formation, burial, deformation, uplift, erosion and renewed deposition extending across almost two billion years. Rodinia broke apart hundreds of millions of years before the first dinosaurs appeared, while the Colorado River began cutting the modern canyon only within the last several million years. The basement rocks, the Great Unconformity and the canyon that now exposes them belong to profoundly different chapters of Earth’s history.

The so-called “missing billion years” is therefore not an embarrassing absence of evidence for geologists. The erosional surface is itself evidence: evidence that rocks once present were uplifted and removed before younger sediments were deposited upon what remained. The variable depth of that erosion, the tilted and truncated strata below the unconformity, and the contrasting depositional environments above and below it are precisely what a single, indiscriminate Flood should not have produced.

Creationists can offer retreating Flood water, breached post-Flood lakes or some other improvised catastrophe, but they cannot agree on a mechanism or make it consistent with the dated rocks, ancient landscapes and successive geological events preserved in the canyon walls. Geologists may debate the details because the evidence gives them details to debate. Creationists have only a conclusion imposed in advance—and nearly two billion years of rock recording why it is wrong.

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