“Volcanoes” in Florida, Georgia, North Carolina and Tennessee explained
An article entitled “Georgia’s Secret Volcanic Range” has attracted considerable readership and controversy. The article was written after a POOF reader described finding small amounts of obsidian in the Pidgeon Mountain Range of Northwest Georgia, which is immediately east of the Cumberland Plateau in Alabama. I wrote an article which recounted newspaper reports of volcanic activity at Pigeon Mountain in 1857. Some tectonic activity continued at Pigeon Mountain until the 1886 Charleston, SC Earthquake.
To several people writing in, it seemed implausible for volcanoes to exist in regions of sedimentary rock. Those comments associated with the Fernbank Science Center in Atlanta became increasing pejorative . . . calling me a hoaxter, fraud, dangerous, dishonest, unscientific and spreader of fake news. These persons, claiming to be professional or semi-professional geologists, stated as facts that there were no volcanoes and no diamonds in the Southeast. They said that it was impossible to have volcanoes, where there was sedimentary rock strata.
Actually, up until the 1886 Charleston Earthquake, there was a minor type of volcanic activity documented in Northwest Florida at the Wakulla “volcano,” plus several locations in the mountains of Georgia, western North Carolina and extreme eastern Tennessee. There was a less intensive outbreak of this same type of activity near Asheville, NC in the 1980s, which was associated with minor earthquake activity 270 miles away in the Charleston, SC area and in eastern Tennessee. Residents in Tennessee, North Carolina and Northwest Georgia have repeatedly reported hearing explosions from mountaintops in the Great Smoky, Pisgah, Unaka, Cohutta and Pigeon Mountain Ranges.
The geology profession acknowledged and in a general way, explained the existence of volcanic activity in the Southeast over 140 years ago. Apparently, those persons, who made the pejorative comments, were not provided this information in collage. However, before we discuss the findings of geologists at a conference held in 1874, we will give readers some background information.
Southern Highlands Geology 101
The Southern Highlands today consist of the remnants of several mountain-building epochs, over many hundreds of millions of years. The oldest mountains have been worn down to the point that they a generally not visible except at Pine Mountain, northeast of Columbus, GA and several small mountains in the Metropolitan Atlanta Area. Famous Stone Mountain, 16 miles east of Atlanta, is a monadnock or the granite core of what was once a massive volcano. The older mountains were created by the collision of Africa and North America. At one time, they were the height of the Rockies. Younger mountains in Northwest Georgia, North Alabama and Eastern Tennessee were created by the folding and erosion of sedimentary rocks. Massive volcanoes once erupted in what is now the Atlanta Metropolitan Area and along a fault line that now defines the Cohutta, Unaka and Great Smoky Mountains.
Structural engineers and architects absolutely have to understand geology, because if we don’t, buildings will fall down. So the condescending comments from readers that assumed I was ignorant of geology were off base. For example, both in the Shenandoah Valley and in Bartow County, GA, I had to design special concrete footings for buildings because the dolimitic limestone beneath the surface is prone to expand in the winter and contract in the summer. In both regions the sub-strata rocks look like Swiss Cheese. These cavities fill with water seasonally. The limestone slowly dissolves and sometimes collapses. One section of my farm in the Shenandoah Valley was at least a foot lower in August than early April!
Geology classes at Georgia Tech make students aware that North Georgia and Western North Carolina were violent volcanic regions eons ago. There are still active faults in the region and so when I design a building in Northwest Georgia, I must use Zone Two or Three seismic design structural reinforcement.
However, there is a line of extremely ancient, extinct volcanoes in North Georgia, which are totally unrelated to the fault lines or major mountain ranges. It is now theorized that the cause of these volcanoes was holes in the earth’s crust, which allowed magma to push upward near the surface. This is what is still creating the Hawaiian Islands. A recent geological report theorizes that there was once a volcanic island chain like the Hawaiian Islands off the coast of the Carolinas. The North American and broken chunk of the African Plate, attached to North America, overrode these islands. Their lava punctured through the continental plates, but eventually ran out of magma.
On a field trip, a professor showed us a line of cone-shaped mountains that stretch from near the Savannah River to the edge of the Great Appalachian Valley. These are the remnants of ancient volcanoes. The vector of this line crosses the Blue Ridge Mountain Escarpment. It does not run at the same angle as the Blue Ridge Mountains. A professor mentioned that there are still several extinct or dormant volcanic vent holes or fumaroles in North Georgia and western North Carolina. He stated that in the past, large, high quality diamonds had been found on the surface of North Georgia and speculated that at least some of these vent holes might be diamond tubes.* However, NO ONE ever mentioned to us that there had been a form of volcanic activity in the Southern Highlands during recent times.
*The governor of the Spanish Province of La Florida paid 5,000 crowns for an enormous diamond that a trader obtained from the town that we now call the Track Rock Terrace Complex. The Spanish called the town, Copal. There was a commercial gem mine at Track Rock Gap in the late 1800s and early 1900s.
During the 1970s and 1980s, there were a series of sharp explosions in the Craggy and Black Mountains near Asheville, plus the Pisgah and Smoky Mountains along the North Carolina and Tennessee State Line. The sharp explosions in the Pisgah Mountains were associated with massive rock slides. Local “rock experts” were particularly confused because the explosions had occurred at locations that were igneous, metamorphic AND sedimentary rock strata. They assumed that the explosions could not have come out of the earth in sedimentary regions.
My farm was at the foot of 6,105 feet tall Craggy Dome Mountain, I heard some of the explosions. They sounded like the sharp crack of lightning bolts nearby, but there were few clouds in the sky, when most explosions were heard by North Carolina residents. Residents living in the area between Asheville and Hendersonville, where the rocks are limestone, also smelled sulfur type odors after these explosions. On several occasions the rock slides completely blocked Interstate 40 and did millions of dollars of damage to roads and bridges, so geologists from North Carolina State University and the US Geological Survey were brought in to thoroughly research the region’s geological history.
The Asheville Citizen-Times published a summary of the geological report. This is when I first learned about recent volcanic activity in the Southeast. The geologists pinpointed the explosions to be at locations where there had been volcanic activities up until the 1886 Charleston Earthquake. These activities included rocks being exploded out of the ground, a red glow at night, volcanic smoke that smelled like sulfur and flames shooting out of the ground. The report also mentioned such activities occurring in the Pigeon Mountains of Georgia. However, at the time I had no clue where the Pigeon Mountains were.
The geologists stated that the explosions were caused by superheated gas and steam breaking though cracks in the bedrock and reaching the surface under high pressure. They observed that one of the craters in the Southern Highlands were created by the explosions by decomposition of the calcium carbonate, which exposed to super-heated steam. It didn’t matter what kind of rock. The geologists observed that one of the most frequent locations of proto-volcanic activity and earthquakes was near Hot Springs, NC . . . which itself is near the Great Smoky Mountain Fault Line. The rocks here are sedimentary stone.
The geologist, who stated that volcanoes cannot occur in limestone strata, was absolutely wrong. Several of Mesoamerica’s largest limestone caves are near active or dormant volcanoes. The caves were initially created by superheated gases dissolving the limestone. That will be discussed later in the article.
The geological report stated that the heat and gases were coming from active fault lines. The geologists had no explanation as how a fault near Charleston, SC could create Stage One volcanoes 300-400 miles away in western North Carolina, Tennessee and Georgia. However, there are active earthquake zones around fault lines in the Southern Highlands, which parallel the Great Smoky Mountains, plus are under the Pigeon Mountains and Lookout Mountain in Georgia and Alabama.
In its incredible wisdom, the TVA built two nuclear power plants over an active fault line. The US Army Corps of Engineers built one of the world’s tallest earthen dams over the Cartersville Fault in Northwest Georgia. This fault is assumed to be inactive . . . but is it? There were absolutely no seismic reinforcements placed in Carters Dam.
What residents of the Southern Highlands experienced in the 1800s was the first stages of volcanic eruptions. However, with the possible exception of one or two craters in Haywood County, NC, no lava came to the surface. The geologists were asked by reporters, if these gassy volcanoes in the Southern Mountains could turn into the more violent type of volcanoes, which spewed lava. The answer was “yes, but not likely.” If the gases have cut holes through the bedrock, hot magma often follows their paths in other regions of the world. Do scientists really know for certain that these explosions in the Southern Highlands are not the beginnings of real volcanoes some time in the near future? The answer was, “No, but we hope we are right.“
Volcanic activity in limestone regions
Anyone who has spent much time in southern Mexico knows that volcanic activity and sedimentary bedrocks can coexist. Blasts of super-heated steam and tubes of lava have pushed through deep layers of sedimentary rock to create anything from massive caverns to thermal springs to 18,491 feet tall Orizaba Volcano, pictured above. There are also numerous vent holes, like those found in the Southern Highlands, which were considered sacred by the Mesoamerican peoples and the ancient Greeks. The holes were believed to be passages to the underworld. The Oracles of Delphi were located over a vent hole. Thus, the original attractions of Track Rock Gap were both its gems and its vent hole.
An unusual chemical characteristic of calcium carbonate, CaCO3 , makes both limestone and metamorphosed sedimentary rocks, such as marble, extremely vulnerable to volcanic gases and super-heated steam. Calcium carbonate is principal component of limestone, marble and conglomerate. Calcium carbonate has a relatively low melting point, which makes it an excellent flux for utilitarian ceramics. However, when part of stone, it begins decomposing into Calcium Oxide (CaO) at around 1000 degree F. or slightly lower. When subjected to superheated steam, limestone and marble quickly decompose and become calcium hydroxide, a highly caustic substance.
There is an extremely deep vertical hole in Pigeon Mountain, which some eologists have interpreted as being created by eons of dripping water . . . yet they have no explanation as to why this chamber, which is quite similar to a vent hole, formed at that location and nowhere else. Logic would suggest that such a phenomenon would be at a low point of a valley, not within a mountain peak. Residents of the region in the 1800s stated that the explosions associated with Pigeon Mountain came from the mouth of this chamber and a nearby crater. As stated earlier, “gas” and “steam” volcanoes can create craters . . . some with the identical appearance and size of collapsed calderas.
July 16, 1874 conference in Washington, DC
Reports by Union troops during the Civil War and Reconstruction of strange explosions heard from the mountains of North Carolina, Georgia and eastern Tennessee induced the American Philosophical Society to ask General Thomas L. Clingman of North Carolina to present a report on the phenomena. Clingman devoted the last 35 years of his life to the scientific study of the Southern Appalachians. Clingman’s Dome in the Great Smoky Mountains is named after him.
Clingman stated that there were several locations where violent explosions had occurred from below the surface of mountain tops, leaving holes in the ground, shattered rocks and flattened trees. Most craters were circular and four to five feet wide. However, after a loud explosion near Franklin, NC, a crater was visible, which was about three feet wide and a mile long. The odor of sulfur lingered around the craters long after they ceased emitted hot smoke. The rocks and trees around the craters were scorched. Even though Clingman was a professional surveyor, it was impossible for him to measure the depth of these craters.
Clingman stated that from the earliest settlement of western North Carolina in the late 1700s, settlers had repeatedly experienced earthquakes in many locations around the region, which were soon followed by explosions and craters appearing near the highest elevations of mountains and ridges. His interpretation of these events was that the earthquakes permitted some magma to push higher into the surface rocks, which then created very hot gasses. These gasses were able to push their way upward because their high heat shattered the rocks. Apparently, dense crystalline rocks were sealing the breach before magma could flow upward to the surface.
Clingman has seemed to “hit the nail on the head.” At every location where the gas volcanoes have appeared, there are faults deep within the earth nearby, or directly under the crater. There is an active fault line and earthquake zone under the Pigeon Mountain Range. These mountains could have well been coated with a mantle of solidified lava eons ago, which has since then eroded off . . . except for a few pieces of obsidian.
The gas primarily explodes out of the ground at the peaks of mountains because the mountains were created by the folding of rocks and the exposed ends of these rock strata occur at the tops of mountains.
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