A study led by the University of Southampton proposes that a colossal cliff system, known as the Great Escarpment of Laurentia, formed about 800 million years ago as the supercontinent Rodinia fragmented. The escarpment may have reached roughly one kilometer in height and extended for thousands of kilometers along western North America, crossing areas that today include Arizona, Utah, Idaho, Wyoming, Colorado, Texas, Oklahoma, Arkansas, Missouri and Illinois.
Over tens of millions of years, erosion along this immense boundary gradually migrated inland, removing an estimated five to ten kilometers of rock in some locations. This process progressively brought ancient crystalline basement rocks to the surface, which are now visible in the Grand Canyon in southern Arizona.
The Grand Canyon preserves a geological history stretching back about two billion years, yet more than half of that rock record is absent, a feature known as the Great Unconformity. The researchers suggest the ancient escarpment provides a mechanism for this massive gap, linking the missing strata to tectonic uplift and erosion during continental rifting.
To reconstruct the lost landscape, the team combined plate tectonic reconstructions with landscape evolution models. Their results indicate the future Grand Canyon region sat in a position relative to the continental edge similar to modern escarpments in South Africa and Brazil, supporting the interpretation of a long-lived tectonic landscape.
The study, published in Geology, involved scientists from the University of Southampton, GFZ Helmholtz Centre for Geosciences, University of Potsdam, and University of Illinois Urbana-Champaign. Lead author Professor Thomas Gernon said the findings could help geologists reinterpret other ancient continental interiors where similarly large gaps occur in the rock record.
Beyond the Grand Canyon, the escarpment may have shaped river paths, determined sediment deposition zones, and influenced the timing of sea-level advances across the continent before the Cambrian explosion. The researchers note that comparing the ancient North American landscape with active escarpments today offers a new perspective on how continents evolve over hundreds of millions of years.
A lost mega-cliff may explain the Grand Canyon’s missing billion years
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