The volcanic history of the Southern Highlands
The Geology Department at North Carolina State University seems to be the sole depository of recent knowledge on this subject.
Did you know that immediately prior to the 1886 Charleston, SC, several minor volcanoes erupted in the mountains of Georgia, North Carolina, extreme eastern Tennessee and near Wakulla, Florida? Some of these fumaroles had been venting hot gasses for decades, but became dormant after the quake. Nevertheless, thermal springs, created by hot rock strata heating water, are still flowing in North Carolina and Georgia.
Ancient volcanism created the vast cornucopia of minerals and metals, which first attracted Native Americans to the Southern Highlands then early colonists then swarms of gold miners. The volcanoes brought many minerals up to near the surface such as gold, copper, iron, quartz crystals, rubies, sapphires and diamonds. Heat and pressure over time created mica and greenstone, which was the stone, preferred by Native Americans for making axes, wedges and ornaments. Jade is a type of greenstone. The volcanic soil in the region also very fertile, particularly if lime (or in ancient times, crushed shells) are added to the soil, crops are abundant.
According to the memoir of Captain René de Laudonnière, commander of Fort Caroline, the exportation of these valuable commodities, particularly mica, greenstone, quartz crystals and gold foil, made the Apalache in northeast Georgia very wealthy. This wealth made possible cultural advancements that did not occur among most indigenous peoples in North America.
The Blue Ridge Mountains and Piedmont, from Pennsylvania to Alabama, are underlain by either igneous rocks or metamorphosed igneous rocks that were created by ancient volcanoes . . . some of them larger than any active volcanoes existing on earth today, except perhaps the Yellowstone Caldera. However, there is another chain of mountains in the Southeast, which cross the Blue Ridge Mountains along a roughly east-west line. They are characterized by cone shaped peaks that sprout from the sides of the Blue Ridge Mountains. Other ancient, extinct volcanoes stand alone or form their own chains. A good example of the latter is the Yeona* Mountain Range, which gave Yonah Mountain its name. There are also Monadnocks in Virginia, North Carolina, South Carolina and Georgia, which are the granite domes or cores of ancient volcanoes.
*Yeona is the Asturian word for a mountain lion. Asturia is the principal gold mining region of Iberia. It also contains Bronze Age petroglyphs identical to those in southwestern Ireland (another gold mining region) and Upper Etowah River Basin in Georgia.
Virginia’s and West Virginia’s “Not supposed to exist” volcanoes
Your eighth grade Natural Science teacher probably told you that volcanoes only exist within regions containing igneous rock. That myth is still carried by many armchair and not-so-well-educated geologists. The theory is that when the depth of sedimentary rock is many thousands of feet, the appearance of a volcano at the surface is impossible. Actually, the type of rock has nothing to do with it. The main conditions required are magma under pressure and a crack in the earth . . . aka a fault line.
Virginia’s tallest mountain Mount Rogers is probably an extinct volcano. Like all Southeastern Mountains, it has never actually been studies to determine if magma is still underneath the mountain, so it MAY be active or dormant, but probably, it is extinct. Mount Rogers was created when magma pushed through over two miles of sedimentary and metamorphic rock.
There are numerous extinct volcanic cones in the sedimentary rock region of western Virginia and eastern West Virginia. The best known of these is Mole Hill near Harrisonburg, VA. Most are cone-shaped hills composed of igneous rocks, protruding through limestone bedrock. None have been studied by volcanologists to determine their status, but all are assumed to be extinct.
Gas volcanoes and volcanic vents
There is even a type of volcano, which contains little or no igneous rock in the cone. It is called a gas volcano. Water, super-heated by proximity to magma, can become highly acidic, when it comes in contact with such minerals as sulfur. In particular, sulfuric acid eats through limestone rather quickly . . . producing large quantities of carbon dioxide, sulfur hydroxide and steam. The gas pushes upward to the surface, eating away calciferous rocks. The result is what looks like a vertical cave. Further gas eruptions throw out boulders, stones and liquified calcium carbonate. Over time, a cone is created.
The little-known minor volcanoes in North Carolina and Georgia occur in regions, which experienced intense volcanic activity for several hundred million years, but are theoretically inactive now. However, the truth is that volcanologists has ever studied any of these mountains. So, we do not know if they sit atop large pools of magma.
Thomas Clingman, a natural scientist for whom Clingman’s Dome in the Great Smoky Mountains is named, studied several of the mini-volcanoes, immediately after their eruption in 1886. The most enigmatic was a 1000 feet (300 m) long crack in a mountain near Franklin, NC. Clingman did not find lava rocks at any of these sites. What he did find were rocks of varying size, which had been spit out of the mouths of some of these holes, burned vegetation near the craters and a sulfurous coating on the nearby soil and vegetation.
Clingman theorized that these mini-volcanoes were volcanic vents, which acted as chimneys for geological forces deep within the earth. The heat and gases, created by friction in faults, were brought to the surface. He could not explain how a fault line near Charleston, SC could trigger these volcanic vents to erupt over 300 miles away in the Florida Panhandle, northern Georgia and western North Carolina.
Recent volcanological research at North Carolina State University
The geologic record suggests volcanic activity in what is now the Southeastern United States 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 again while these same plates were colliding. A massive layer of volcanic ash was spread over much of the Southeast around 442 million years ago. It is now bentonite. The quantity of volcanic ash could only have been created by a caldera the size of Yellowstone National Park . . . or larger.
During the first phase, 840 to 800 million years ago, eruptions occurred under the ancient Lapetus Sea and on land. Volcanic ash and lava flows deposited underwater and interbedded with layers of mud and sand on the northwestern corner of North Carolina and 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 10,000 feet (3,000 m) of volcanic rock.
The second phase of volcanic activity, beginning around 750 million years ago and lasted over 300 million years. It ccurred along an arc of island volcanoes on the Avalon Terrane, a collision zone between the Lapetus Sea and the Theic-Rheic Ocean. It is believed that another chain of islands caused the volcanoes in northern Georgia. 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.
Volcanic eruptions may have occurred during the middle Eocene epoch, about 47 million years ago, in the northern and western regions of North Carolina, but erosion has removed all cones or other evidence of such activity. The connection between minor volcanic eruptions in the Western North Carolina Mountains and the Charleston, SC fault lines is not fully understood.
1954 geological study of Atlanta Area mountains
In the 1950s, geologists from the University of Georgia and Oak Ridge National Laboratories used newly developed nuclear science to determine the history of a granite shield in the Georgia Piedmont. The team determined that the large mass of granite bedrock was created by a magma caldera of immense size, which pushed up through the sedimentary rocks. Its rise was calculated to have about 291 million years ago.
The eruption of this caldera would have been a 100% extinction event for a 500 mile radius. Igneous and volcanic rocks north of the Brevard Fault (Chattahoochee River) were completely unrelated to the Stone Mountain Caldera. We will now look at extreme northeast Georgia, where volcanic cones are still visible. They have never been studied individually by geologists, so it is really not known when they erupted . . . but the probable period is between 220 million and 47 million years ago . . . but perhaps a few continued to erupt in a much later period.
1955 geological study of Nacochee and Soque Valleys, Georgia
In the mid-1950s, a state-funded geological study of the upper Chattahoochee and Soque River Basins determined that it was once a region of extreme volcanism. Several volcanic cones cut through the much older volcanic rock of the Blue Ridge Mountains and Southern Piedmont to create a chain of cones and calderas, which appeared from east to west across what is now Georgia. The geologists found that the primary rock, immediately under the surface of the Soque and Tallulah Rivers, plus Sautee and Chickamauga Creeks in the eastern Nacoochee Valley was rhyolite. Rhyolite is associated with calderas . . . also known as super-volcanoes.
The state geologists mainly examined road cuts to determine the region’s geological history. Intimate contact with the terrain of the region produces a much more complex understanding of the past, but also raises many questions. On my relatively small tract of land at 1814 feet elevation on Sautee Ridge can be found virtually ALL the types of volcanic rock, which are described in typical references. There are major variations in the color and texture of the ryholite on this ridge. Much of the underlaying stone around my house looks like gypsum plaster was poured on the ocean floor or a river bed. The dense content of quartz crystals give the stone an abrasive texture that will literally cut your hands, if you are carrying the stones without gloves. There are also stones that literally contain worn river pebbles. These were obviously created when lava struck shallow water.
Much more recent volcanic activity
There is something mysterious that cannot be explained with the current geological orthodoxy. In the clay sub-soil and black top soil above the solid rhyolite, I have been finding lava bombs! These are dark charcoal gray scoria (fresh lava rock) and pumice, varying in size from a potato to a cantaloupe. I am putting them on display along the oval rock wall enclosure that I am building in my front yard. Otherwise, no one would believe me, I fear. According to the official geological history of this region, volcanic activity in this region ceased many, many millions of years ago. However, according to a color chart, used by the US Geological Service to determine the age of volcanic rock in Hawaii, these stones are from 1000 years old to being NEW. I have also found (so far) one lava bomb, which contains so much iron and nickel that it is magnetic! In other words, somewhere around here there is a volcano, which is not extinct, but only dormant.
An extinction event in the Northeast Georgia Mountains
The 1693 Map of North America by Robert Morden showed the town of Apalache, where the Sautee Community is now located in the Nacoochee Valley of Georgia. That same year, Governor James Moore of Carolina led a mounted troop of British Redcoats to the edge of the Nacoochee Valley and observed Spanish-speaking gold miners smelt gold with the help of their Apalache-Creek laborers. The town of Apalache never appeared on another map.
In 1939 survey of the Nacoochee Valley Bottomlands, archaeologist Robert Wauchope found a one to fifteen feet deep layer of almost sterile (no artifacts) alluvial sand, which separated a layer rich in 16th/17th century Spanish artifacts and Lamar Culture (Creek Indian) potsherds from a thin layer of 18th century British artifacts with no Native American artifacts. Wauchope searched the Nacoochee Valley for a year, but never could find a Cherokee village from any period. All of the Native American artifacts were either from ancient times or were uniquely associated with the ancestors of the Creek Indians. He interpreted this sterile layer as being the result of an unimaginable natural catastrophe, but could not fathom what could create so much sediment. The Chattahoochee River is just barely a river, when it enters the Nacoochee Valley.
That is one of the questions that we are currently trying answer. “What completely devastated the Apalache-Creek and Spanish occupation of the Nacoochee Valley?”
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