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Volcanoes

by William G. DiNome, 2006Ashe formation. Image courtesy of the McKinney Geology Teaching Museum, Appalachian State University.

The geologic record suggests volcanic activity in what is now North Carolina primarily occurred in two phases of the middle Proterozoic era, between 850 and 500 million years ago, first while the ancient North American and Euro-African plates were moving apart, then while these same plates were colliding. During the first phase, 840 to 800 million years ago, eruptions occurred under the ancient Iapetus Sea and on land. Volcanic ash and lava flows deposited underwater and interbedded with layers of mud and sand are now part of the Ashe Formation stretching from Ashe and Watauga Counties in North Carolina into Franklin County, Va. The first eruptions on land occurred about 820 million years ago on the Piedmont Terrane, along the present North Carolina-Virginia border in the environs of Mount Rogers. These eruptions continued for at least 220 million years and deposited some 3,000 meters of volcanic and sedimentary rock.

The second phase of volcanic activity, beginning around 750 million years ago and lasting more than 300 million years, occurred along an arc of island volcanoes on the Avalon Terrane, a collision zone between the Iapetus Sea and the Theic-Rheic Ocean. Intense folding and metamorphism have destroyed most evidence of these eruptions, but the rocks created are present in the Carolina State Belt stretching southward through the midsection of the state. The eastern boundary of the belt is undetermined as it lies beneath the Coastal Plain, while the western boundary roughly passes near Greensboro, Thomasville, Lexington, Salisbury, Charlotte, and into South Carolina. Remnant volcanic necks and masses of igneous rock are evident in Orange and Chatham Counties, suggesting an early center of volcanic activity near Chapel Hill, dated at around 700 million years old, and near Hillsborough, dated at about 650 million years old.

Volcanic eruptions may have occurred during the middle Eocene epoch, about 47 million years ago, in the northern and western regions of the state, but erosion has removed all cones or other evidence of such activity. Also, volcanic ash deposits (bentonite) in the Castle Hayne Formation in the Coastal Plain are not believed to be native to the region, but possibly deposited by winds from a volcanic center in Virginia or from eruptions forming the island of Bermuda. There are no known active volcanoes in North Carolina today despite some geologic instability on the coast.

References:

Fred Beyer, North Carolina, the Years before Man: A Geologic History (1991).

Mary-Russell Roberson and Kevin G. Stewart, The Geologic Story of the Carolinas: A Field Guide (2006).

Additional Resources:

Geological Society of American, Bulletin of the Geological Society of America, volume 20.

Image Credit:

Ashe formation. Image courtesy of the McKinney Geology Teaching Museum, Appalachian State University. Available from http://mckinneymuseum.appstate.edu/rock-garden/ashe-formation (accessed July 30, 2012).

 

Comments

Comment: 

How can I get more detailed information about volcanic activity in the Chapel Hill area?
I've already seen information about the Eno River Basin activity around Hillsborough, and am looking for information that would relate to the Morgan Creek area.

Comment: 

Hi Susan,

Thanks for visiting this article on NCpedia and taking a minute to ask your question. And that's a really good question!  

There are a number of government resources that you may want to start with for both historic and current volcanic and seismic activity in the U.S.

You may also want to contact our reference staff here at the Government & Heritage Library (or the reference staff at your local public library).  They can help you get started in your research. Here's the link to their contact information on our website http://statelibrary.ncdcr.gov/contact.html

A copy of this email is also being sent to the email address provided with your comment.

Good luck in your research!

Kelly Agan, NCpedia Staff

 

Comment: 

Volcanic ash is very evident if one digs down 10-30' south of Harrisburg. Also dikes and sills have been captured in pictures from pits dug. Volcanic bombs are being found near the surface. I would guess that there was more ancient volcanic activity here than officially accounted for.

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Copyright notice

This article is from the Encyclopedia of North Carolina edited by William S. Powell. Copyright © 2006 by the University of North Carolina Press. Used by permission of the publisher. For personal use and not for further distribution. Please submit permission requests for other use directly to the publisher.

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