THE BIRTH OF STONE MOUNTAIN: A Geological Biography

     The story of Stone Mountain’s origin is just as any birth, just as any beginning: the story starts before conception. In the same manner as biology is used to explain reproduction of living things, geology is used to explain the formation of mountains. The familiarity of plate tectonics helps create a stage on which this story will unfold. Plate tectonics, which is a new theory that is widely accepted yet debated on its smaller details among geologists, basically states that the Earth’s surface consists of several different plates that are consistently moving at the rate of a few centimeters per year. Literally, “all the world’s a stage” where Stone Mountain makes its début and remains a present-day legend.

     Once upon a time, about 300 million years ago, while all the continents were shifting toward each other to form one supercontinent called Pangaea, there was a landmass named Laurentia on a collision path with a much bigger landmass named Gondwana. Because they were traveling as slow as a fingernail grows, their seemingly gradual encounter actually ended up as a violent crash with dramatic changes to the Earth’s surface. The two advancing continents shattered the ocean’s crust and dislodged the smaller bodies of land located in between. Gondwana with its powerful, gigantic structure uplifted and thrust the fragmented ocean’s crust and the small bodies of land into Laurentia. Because the crust and the firmer, cooler part of the outer mantle, which are referred together as the lithosphere, are floating on top of a mushier, extremely hotter part of the outer mantle, which is referred to as the asthenosphere, the pile-up was steadily intensified resulting in the buckling, folding, and wielding of the two landmasses. The Alleghenian orogeny is what the geologists call this monstrous mountain formation that gave the final rise to the Appalachian Mountain chain’s lower, much longer section. Yet underneath, more upheaval arose.

     Because of the newly, exceedingly thickened crust, there were additional tremendous pressure and extreme heat that caused the rocks within the crust to partial melt forming many pools of magma. In Mother Earth’s womb, Stone Mountain was implanted about 8 miles deep as one of these huge pools of magma. This egg-shaped pool of magma was incubated by the complex dynamics of extreme force and temperature including the subduction of the oceanic crust, which occurred when the ocean between the two shifting continents was swallowed and shoved underneath. In just a few million years or so, the magma cooled, solidified, crystallized, and eventually evolved into a huge igneous rock, or even more precisely a huge granite rock. By the late Triassic period, 200 million years ago, the continents started to drift apart awfully slowly that during the Jurassic period, the dinosaurs and other species roamed the partially connected continents. By the end of the Cretaceous period, roughly 65 million years ago, the buried Stone Mountain was left behind in the continent that will become the modern day North America, and the other continent will become the modern day Africa.

     As the periods in the Cenozoic era started to creep by, Stone Mountain nested protectively below as a pluton, which is a geological term for a body of intrusive igneous rock that is usually huge in size and not tabular. This particular type of igneous rock is classified as granite that is mostly made up of quartz, feldspar, and mica. Meanwhile above, Mother Nature’s powerful forces were busy at work eroding, wearing down, and reshaping the Earth’s surface. Due to this persistent process of erosion, Stone Mountain shyly, yet boldly peeped over the worn down land. Weathering kept on breaking up and pushing away the surrounding soil. Around 10 million years ago, the forces of nature had unearthed over 200 feet of the seemingly growing, young Stone Mountain. Despite that some of the minerals—especially quartz—giving the granite its steel-like hardness, Stone Mountain is vulnerable to nature’s elements. The dome shape is enriched by these weathering elements exfoliating the exterior layer by layer, sheet by sheet: hence the geological term, exfoliation sheeting. Just a million year ago, in the Quaternary period, Stone Mountain became a unique monadnock, which is a geological term for an isolated mountain, permanently rooted in the Piedmont region of Georgia.

      Today, over 800 feet of Stone Mountain (7.5 billion cubic feet, 1.3 miles long, and 0.6 miles wide, and coverage of 583 acres) is exposed, yet underneath much more is left for millions of years to come. This gigantic granite rock’s birth may be similar to other births such as the nearby Panola Mountain, but it flourished into an appealing, distinctive, well-rounded individual. Evidence like ancient artifacts, granite quarry, memorial carving, numerous man-made recreational structures like the sky-ride, and worn footpaths attests to humans’ attraction and growing presence at Stone Mountain. On one hand, the increased flocking of humankind over the years adds to the environmental destruction, and on the other hand countless people such as geologists, historians, environmentalists, nature-lovers, and so forth work hard to protect and preserve Stone Mountain. To this day, Stone Mountain bares noticeable scars and other features depicting its life history.