Researchers from North Carolina State University noticed that a portion of the Appalachian Mountains in western North Carolina near the Cullasaja River basin was topographically quite different from its surroundings.
They found two distinct landscapes in the basin: an upper portion with gentle, rounded hills, where the average distance from valley to mountain top was about 500 feet; and a lower portion where the valley bottom to ridgeline elevation difference was 2,500 feet, hills were steep, and there was an abundance of waterfalls. The researchers believed they could use this unique topography to decipher the more recent geologic history of the region.
The Appalachian mountain range was formed between 325 to 260 million years ago by tectonic activity – when tectonic plates underneath the earth’s surface collided and pushed the mountains up. Around 230 million years ago, the Atlantic Ocean basin began to open, and this also affected the regional topography. But geologists knew that there hadn’t been any significant tectonic activity in the region since then.
“Conventional wisdom holds that in the absence of tectonic activity, mountainous terrain gets eroded and beveled down, so the terrain isn’t as dramatic,” says Sean Gallen, NC State graduate student in marine, earth and atmospheric sciences. “When we noticed that this area looked more like younger mountain ranges instead of the older, rounded, rolling topography around it, we wanted to figure out what was going on.”
Gallen and Karl Wegmann, an assistant professor of marine, earth and atmospheric sciences at NC State, decided to look at the waterfalls in the area, because they would have formed as the topography changed. By measuring the rate of erosion for the falls they could extrapolate their age, and therefore calculate how long ago this particular region was “rejuvenated” or lifted up. They found that these particular waterfalls were about 8 million years old, which indicated that the landscape must have been raised up around the same time.
But without tectonic activity, how did the uplift occur? Gallen and Wegmann point to the earth’s mantle as the most likely culprit. “The earth’s outer shell is the crust, but the next layer down – the mantle – is essentially a very viscous fluid,” Wegmann says. “When it’s warm it can well up, pushing the crust up like a big blister. If a heavy portion of the crust underneath the Appalachians ‘broke off,’ so to speak, this area floated upward on top of the blister. In this case, our best hypothesis is that mantle dynamics rejuvenated the landscape.”
The researchers’ findings appear in Geological Society of America Today. Del Bohnenstiehl, NC State associate professor of marine, earth and atmospheric sciences, contributed to the work.
Note to editors: Abstract follows.
“Miocene rejuvenation of topographic relief in the southern Appalachians”
Authors: Sean F. Gallen, Karl W. Wegmann, and DelWayne R. Bohnenstiehl, North Carolina State University
Published: Geological Society of America TodayAbstract:
Tracey Peake | EurekAlert!
Natural regeneration of tropical forests helps global climate mitigation and forest restoration
23.05.2016 | National Science Foundation
Researchers find that Earth may be home to 1 trillion species
23.05.2016 | National Science Foundation
Characterization of high-quality material reveals important details relevant to next generation nanoelectronic devices
Quantum mechanics is the field of physics governing the behavior of things on atomic scales, where things work very differently from our everyday world.
When current comes in discrete packages: Viennese scientists unravel the quantum properties of the carbon material graphene
In 2010 the Nobel Prize in physics was awarded for the discovery of the exceptional material graphene, which consists of a single layer of carbon atoms...
The trend-forward world of display technology relies on innovative materials and novel approaches to steadily advance the visual experience, for example through higher pixel densities, better contrast, larger formats or user-friendler design. Fraunhofer ISC’s newly developed materials for optics and electronics now broaden the application potential of next generation displays. Learn about lower cost-effective wet-chemical printing procedures and the new materials at the Fraunhofer ISC booth # 1021 in North Hall D during the SID International Symposium on Information Display held from 22 to 27 May 2016 at San Francisco’s Moscone Center.
Staphylococcus aureus usually is a formidable bacterial pathogen. Sometimes, however, weakened forms are found in the blood of patients. Researchers of the University of Würzburg have now identified one mutation responsible for that phenomenon.
Staphylococcus aureus is a bacterium that is frequently found on the human skin and in the nose where it usually behaves inconspicuously. However, once inside...
Using ultrashort laser pulses an international team at the Max Planck Institute of Quantum Optics and the Ludwig-Maximilians-Universität Munich has managed to manipulate the positions of atoms in hydrocarbon molecules.
Light can conduct the play of atoms and molecules in the microcosm. Humans manage to interfere with this play. Researchers from the Laboratory of Attosecond...
20.05.2016 | Event News
19.05.2016 | Event News
17.05.2016 | Event News
23.05.2016 | Information Technology
23.05.2016 | Architecture and Construction
23.05.2016 | Earth Sciences