Geologists Find New Origins of Appalachian Mountains

Nov 16, 2006
Geologists Find New Origins of Appalachian Mountains
In this graphic, "Laurentia" represents Laurussia in one stage of the continent shift. Art by: Christina Ullman

Geologists have developed a new theory to explain how and when the Appalachian Mountain range was created. Their research redraws the map of the planet from 420 million years ago.

The scientists recently discovered a piece of the Appalachian Mountains in southern Mexico, a location geologists long had assumed was part of the North American Cordillera. The Cordillera is a continuous sequence of mountain ranges that includes the Rocky Mountains. It stretches from Alaska to Mexico and continues into South America.

For the past decade, geologists have collected information from Mexico’s Acatlán Complex, a rock outcropping the size of Massachusetts. As they uncovered each new piece of data from the complex, evidence contradicting earlier assumptions about the origins of that part of Mexico emerged.

“It was a story that had the Appalachians written all over it,” said Damian Nance, Ohio University professor of geological sciences and lead author of an article detailing the findings, which was published in the October issue of Geology. “This will change the way geologists look at Mexico.”

It also changes existing theory regarding the creation of the Appalachians, which has radically altered scientists’ understanding of the planet’s geography, said Nance. Age data, newly unearthed fossils and chemical analysis of the rocks show that the complex is much younger than previously thought. It records a pivotal part of the Appalachian story not preserved elsewhere.

According to the conventional map of 420 million years ago, two main land masses were separated by the Rheic Ocean. In the south sat Gondwana, a supercontinent consisting of South America, Africa, India, Australia and Antarctica. To the north was Laurussia, made up of North America, Greenland, Europe and part of Asia. The old map showed the Acátlan Complex attached to Laurussia. The complex broke off Gondwana about 80 million years earlier, drifted toward North America along with the other land masses, closing an older ocean, known as the Iapetus Ocean, as it did so. The collision created the Appalachian Mountains.

The new map looks rather different.

Evidence collected by Nance and his colleagues from rocks in the Acatlán Complex shows that its collision with Laurussia actually occurred about 120 million years later. The rocks once existed on an ancient ocean floor, but this ocean has proven to be the Rheic, not Iapetus as previously thought.

The explanation, Nance and his fellow authors say, is that the Acatlán Complex was originally attached to Gondwana. Gondwana and the complex eventually slammed into North America, closing the Rheic Ocean in the process. This cataclysmic crunch of continental plates formed the goliath land mass known as Pangea, Nance said, and created the Appalachian Mountains.

“We believe we have found the missing piece of the Rheic suture where Gondwana and North America converged,” said Nance. “All the evidence point to that and, as far as we know, it is the best preserved piece of this puzzle in North America.”

Now geologists from around the world, funded by the United Nations Educational, Scientific and Cultural Organization (UNESCO), are expanding the search for evidence of the Rheic Ocean in order to unravel its history from initial opening to final closure.

“We want to see if the ocean opened and closed everywhere at the same time or at different times like a jaw opening and closing. We want to understand the mechanics of these processes,” said Nance.

Source: Ohio University

Explore further: Magnitude-7.2 earthquake shakes Mexican capital

add to favorites email to friend print save as pdf

Related Stories

New study outlines 'water world' theory of life's origins

13 hours ago

(Phys.org) —Life took root more than four billion years ago on our nascent Earth, a wetter and harsher place than now, bathed in sizzling ultraviolet rays. What started out as simple cells ultimately transformed ...

Melting during cooling period

8 hours ago

(Phys.org) —A University of Maine research team says stratification of the North Atlantic Ocean contributed to summer warming and glacial melting in Scotland during the period recognized for abrupt cooling ...

The Isthmus of Panama: Out of the Deep Earth

Apr 01, 2014

As dates in geologic history go, the formation of the slender land bridge that joins South America and North America is a red-letter one. More than once over the past 100 million years, the two great landmasses ...

The Atlantic Ocean dances with the sun and volcanoes

Mar 31, 2014

Natural fluctuations in the ocean temperature in the North Atlantic have a significant impact on the climate in the northern hemisphere. These fluctuations are the result of a complex dance between the forces ...

Recommended for you

Magnitude-7.2 earthquake shakes Mexican capital

18 hours ago

A powerful magnitude-7.2 earthquake shook central and southern Mexico on Friday, sending panicked people into the streets. Some walls cracked and fell, but there were no reports of major damage or casualties.

User comments : 0

More news stories

Magnitude-7.2 earthquake shakes Mexican capital

A powerful magnitude-7.2 earthquake shook central and southern Mexico on Friday, sending panicked people into the streets. Some walls cracked and fell, but there were no reports of major damage or casualties.

New research on Earth's carbon budget

(Phys.org) —Results from a research project involving scientists from the Desert Research Institute have generated new findings surrounding some of the unknowns of changes in climate and the degree to which ...

Health care site flagged in Heartbleed review

People with accounts on the enrollment website for President Barack Obama's signature health care law are being told to change their passwords following an administration-wide review of the government's vulnerability to the ...

Airbnb rental site raises $450 mn

Online lodging listings website Airbnb inked a $450 million funding deal with investors led by TPG, a source close to the matter said Friday.