And the Earth Moved
Earthquake history in Appalachia
You may think that California and the Far East are the places most at risk for earthquakes, but the mountains of the Appalachians have had their share of earth-shattering quakes throughout history. And researchers predict the Eastern mountain range is ripe for more.
A magnitude 2.4 earthquake hit the mountains of North Carolina around Boone and Blowing Rock in August 2014, and an earthquake of magnitude 2.9 struck the same location in August 2013. A magnitude 5.8 quake shook the mountains of Virginia in 2011. Roanoke Rapids and Lenoir, NC, experienced earthquakes in June 2015, at magnitudes of 2.3 and 3.0 respectively.
The Past Catching Up
Dr. Scott Marshall, pictured to the right, the resident geophysicist at Appalachian State University in Boone, conducts research involving fault modeling and how earthquakes occur. He blames the continuing cycle of quakes in the North Carolina mountains on previous occurrences throughout history.
Data supports his theory that most of the quakes in the Appalachians actually are aftershocks from the first big quakes that hit the hills in 1811 and 1812. Those magnitude 7.0 and 8.0 earthquakes created shifts and instability in the subsurface rocks, which were never the same after the big ones. So while the aftershocks out west happen relatively close to the actual quake, it takes much longer for the after-effects of an earthquake to manifest here because of the strength of the Appalachian Mountains and their general lack of seismic activity.
Appalachian Growing Pains
The core of the Appalachian Mountains is the oldest in the history of the continent, formed more than one billion years ago. Fragments have been found on the surface in areas such Blowing Rock (pictured to the right) in North Carolina and on Georgia’s Red Top Mountain. Close to 750 million years ago, the supercontinent started to pull apart like warm taffy, eventually splitting as seawater filled the gap, forming the Oconee Basin.
Volcanoes erupted, creating spots like Whitetop Mountain (pictured to the right) in the southern Virginia Mount Rogers National Recreation Area. In their wakes, the eruptions left valuable rocks, such as granite, quartz, feldspar, emeralds and beryl. During this time, the collision of continental plates created bends and breaks that led to slippage and earthquakes, a common occurrence in the Appalachians millions of years ago. It was these early earthly disruptions that left the hills and valleys we enjoy today.
New Frontiers Shake Up
The 1811 and 1812 earthquakes were called the New Madrid quakes, named after the Missouri town that was the largest settlement on the Mississippi River. The earthquakes were a product of the Reelfoot fault that runs through Tennessee and Missouri and spread to more than 3.1 million square miles. There wasn’t a lot of damage reported because there weren’t many structures built yet. But residents throughout the region felt the earth’s tremors. “The earthquakes caused the ground to rise and fall — bending the trees until their branches intertwined and opening deep cracks in the ground,” reports the United States Geological Survey.
The weakened core of the mountains continues to affect the land’s movement today. There have been more than 2,000 earthquakes reported in the Appalachians since 1973. Marshall and his team at Appalachian State say that the Eastern quakes largely result from the pressure put on the east coast by the movement in the Mid Atlantic Ridge, at the bottom of the Atlantic Ocean.
And when one mountain town feels the earth shaking, you can bet that the ripples are felt for hundreds of miles around. Never is the saying more true that “we are all in this together,” than when you talk about earthquakes in the Appalachians.