Scientists have discovered an enormous ancient geological formation hidden under the Midwestern United States — a billion-year-old rift valley that almost divided the North American continent in half. Referred to as the
Midcontinent Rift
, created around 1.1 billion years ago as a result of tectonic activity that started to rift the continent. This discovery expands upon the investigations outlined in a 2013 study.
published in
Nature
, illuminating this remarkable chapter in Earth’s tectonic past. Despite not completely succeeding in dividing the continent, the rift indelibly marked both the surface geography and the underlying crust.
The Origin and Framework of North America’s Concealed Fault Line
The
Midcontinent Rift
The horseshoe-shaped expanse stretches from Kansas northwards toward Lake Superior and then curves back down towards Michigan. During its prime, this geological formation spanned approximately 1,900 miles (3,000 kilometers), encompassing a basin similar in size to the one mentioned.
modern Red Sea
The rifting commenced when tectonic plates began moving away from each other, allowing magma to ascend and fill the crack with liquid rock. Consequently, extensive layers of basalt, a heavy volcanic stone, were formed as the lava quickly cooled and hardened inside the rift valley.
Today, much of the rift is concealed under deep beds of sediment and remains unseen by casual viewers. Nonetheless, close to Lake Superior, striking exposures of basalt and copper-laden rocks can be found, serving as relics of this geological feature.
volcanic activity
That characterized the rifting phase. These geological formations have been extracted for millennia and continue to be a vital economic asset in the area.
A Spectacular Geological Failure
Even though the rifting process was extensive and vigorous, it suddenly ceased around 100,000 years later—merely a fleeting moment in geologic time. Scientists continue to disagree over precisely what halted this rifting before it could result in complete continental separation. Certain theories propose that distant tectonic activities across the continent, like those involved in forming mountains near the Atlantic coastline, might have played a role. Alternatively, some researchers argue that shifts in mantle behavior or the emergence of a seaway between the old cratons of Laurentia and Amazonia may have been responsible for preventing further rifting progression.
G. Randy Keller
, a geophysics professor emeritus and former director of the Oklahoma Geological Survey, referred to this occurrence as “a remarkable failure.” He elaborated in the
Nature
article, “How that feature could just totally reorganize the crust of the Earth in the Lake Superior region and not manage to break the continent apart is fairly amazing.” This striking paradox highlights the complex interplay of forces shaping Earth’s crust over deep time.
Lasting Geological and Economic Impacts
Though the
Midcontinent Rift
did not succeed in splitting the continent, its legacy endures in both geological formations and natural resources. The volcanic rocks and sedimentary deposits formed during and after the rifting phase created unique structures that influenced the region’s topography and mineral wealth. Copper mining, particularly on Michigan’s Keweenaw Peninsula, traces its origins back to this ancient volcanic activity.
Additionally, modern researchers have begun exploring new resource opportunities associated with the rift. Basalt’s interaction with water can generate hydrogen, a clean energy source, drawing renewed interest from energy companies in the Midwest. This demonstrates how ancient geological events continue to influence scientific and economic endeavors today.
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