Georgia’s geological history is outstandingly fascinating. It is divided into five distinct regions: Piedmont, Ridge and Valley, Blue Ridge, Appalachian Plateau, and Coastal Plains. These regions’ location is best explained by the mechanism of continental plate tectonic collisions that formed the Appalachian more than 300 million years ago.
All these plate collisions triggered other mountain formations, such as Stone Peak, too. It has the most massive exposed mass granite in the world and the world’s third-largest monolith. The Stone Mountain in Northern Georgia, with several unanswered questions, enhances a fascinating past. Nevertheless, Stone Mountain is today known for its elegance and elegant bas relief. Here there were carved three figures from the Confederate States of America; Stonewall Jackson, Robert E. Lee, and Jefferson Davis. Stone Mountain is the host of Stone Mountain Park, which is the main tourist attraction. Besides, that-it plays a significant role both in Georgia’s eco-system and its economy.
Formation of Stone Mountain
The geological history of Georgia is incredibly impressive and is estimated to have lasted a billion years. Influenced by numerous mountain range formations and erosions and geological phenomena such as extreme climatic changes and volcanic eruptions and floods-Georgia’s geology also poses unanswered questions. The accumulation of these geological events has resulted in forming a historic landmark today known as the Stone Mountains. Larry Worthy’s article ‘Stone Mountain Natural History’ (exclusively for The North Georgia, 1994-2011) Stone Mountain, at its highest point, stands a mighty 1683 feet above sea level. It sits on the west side of Lithonia Gneiss granite’s broad belt, although the younger intrusive granite that forms the mountain is entirely different from Lithonia granite.
Commonly referred to as a monadnock granite dome, Stone Mountain’s construction disseminated over many counties and provided a substantial amount of low relief. Many geologists are still pondering the formation of the Stone Peak, with several unanswered questions. Nevertheless, it is safe to say based on checked Literature; water, deserts like conditions, and glacial features played a vital role in its development. During the last stages of Alleghenian Orogeny, which also produced the Appalachian Mountains, the Stone Mountain in Georgia was formed. Technically speaking, the Alleghenian Orogeny’s ‘stress’ and ‘pressure’ have caused massive land uplifts in Northern Georgia to form mountains.
As far as water impacting the formation of Stone Mountain goes, many geologists assume that at one point, Piedmont was higher than the mountain. As millions of years passed, the water steadily eroded, leaving so much of the granite of Stone Mountain exposed. On the other hand, in the Researcher’s view, amid the divergent occurrences of plate tectonic cycles, its formative exposure may be due to heat and pressure within the earth. Also, the desert-like conditions in the area help describe the mineral composition of the various types of rock in the region.
Most Prevalent Rock Types on Stone Mountain
Rocks from the Stone Mountains belong to the three major classifications according to the rock cycle. However, the two most popular categories of rock are metamorphic and igneous rocks. One common rock from the metamorphic group is the Gneiss rock, while the granite is a typical rock example from the igneous group found at the site.
Granite is an intrusive and igneous rock, which is usually semi-coarse or coarse in texture. Stone Mountain is sometimes referred to as the pink granite. The granite is pink in color because of its mineralogy and chemistry. Reviewed Literature dictates that there are at least two known ways for the composition of Stone Mountain’s Granite. Creationresearch.org cites Whitney et al. (1976, pg 1071) “in terms of mineralogy and major and minor-element chemistry, Stone Mountain Granite has a highly differentiated composition brought about by fractional crystallization and fractional melting.” According to creationresearch.org, it is highly composed of feldspar, quartz, microcline, and muscovite with smaller proportions of biotite and tourmaline. Further study also shows that Xenoliths (foreign pieces of rock entrained in the magma) are found in the granite. The Xenolith from the Stone Mountain Granite is composed of two types of metamorphic rocks-Gneiss and amphibolite xenoliths of the country-rock torn from the conduit as the granite ascended through the earth’s crust.
On the contrary, the Gneiss Rock is a metamorphic rock with an intriguing banding. To a person with limited knowledge of geology or a related subject, they will classify the rock with parallel and somewhat irregular banding, which has little tendency to split along the planes. According to the Britannica online encyclopedia, Gneiss is composed of an abundance of Quartz and Feldspar. The same source also dictated that “the mineralogy of a particular gneiss rock is a result of the complex interaction of original rock composition, pressure and temperature of metamorphism, and the addition or loss of components.”
How old is Stone Mountain?
Stone Mountain is estimated to be 350 million years old. Its age has always been referred to as the last stages of the Alleghenian Orogeny, which was the last time North America and North Africa collided in the late Paleozoic time. The Alleghenian Orogeny is referred to as a mountain-building event. According to the online Britannica encyclopedia, the Alleghenian Orogeny occurred almost simultaneously as the Permian Period, which created the Appalachian Mountains. The said source also declared that the Alleghenian Orogeny produced the compressional folding and faulting of the Ridge and Valley Province and Blue Ridge regions in Georgia.
Birth of Stone Mountain
Larry Worthy’s article reveals that Stone Mountain was formed during some intensive folding and faulting that created the Blue Ridge Mountains (even though it’s not a part of its range). The article further went on to state that Stone Mountain was formed by magma deep inside the earth, which then forced its way out of the earth’s molten center. Before the molten rock hitting the air, it stopped, forming the west side of the “pluton.” Several attempts at eruption (breaking through to the surface of the earth) also failed, but indeed added to the dome’s size from west to east. After the pluton formed, it began to cool. Technically since it was formed from magma-the most suitable geological event that could have fostered its creation was a volcano.
Plate Tectonics relative to the creation of Stone Mountain
Concerning an online dictionary, the term’ plate tectonics’ refers to a theory of global tectonics. The lithosphere is divided into several crustal plates, each of which moves on plastic asthenosphere more or less independently to collide with, slide under, or move past adjacent plates. Many geologists believe that the continents were once a part of a large landmass called PANGEA, and they split and drifted away from each other. This splitting and the drifting process produce the presently known continental shapes. Sir Francis Bacon was the first to observe that the continents looked like a jigsaw puzzle.
The most known role of plate movement is the development of mountains. As such, plate tectonics played a significant role in the formation of Stone Mountain through various plate collisions that occurred during the Alleghenian Orogeny and even before, which also created other mountains.
Weathering in Stone Mountain
Weathering may be defined as the process that breaks rocks into smaller pieces. It is only natural for rocks to undergo this process, which is classified under three categories.
Quite often, the process of mechanical weathering that occurs through a freeze-thaw procedure. This procedure occurs when water gets into the tiny cracks in the rocks when the water freezes the crack expands, and once the procedure is repeated, it will result in the rock breaking away.
Very straight forward, this type of weathering occurs when rock is chemically attacked, such as when acid rain attacks limestone causing it to be broken down.
Undoubtedly the most natural of the three- biological weathering causes rocks to be weak as animals and plants break them down. In other words, let’s say there is a giant tree on a rocky hill or mountain, and the roots are so big it causes the rocks to split-this This is an example of biological weathering.
Analysis of Weathering in Stone Mountain
The types mentioned above of weathering can significantly affect the appearance of a geological structure. Concerning Stone Mountain in Georgia, rocks there have undergone and are still undergoing some amount of weathering-particularly physical weathering. Erosion, being classified as a type of physical weathering, is responsible for changes in the rocks’ appearance on Stone Mountain. Soil erosion causes the surface rock to strip away in a way that causes them to be exposed over time. The now exposed rocks which were once buried deep in the earth are no longer subject to the pressure, which would have affected them being at a greater depth. The freedom from pressure causes underlying rocks to expand upwards and develop fractures parallel to the present ground surface. These newly formed structures are now known as exfoliated sheets.
Types of Rocks in Stone Mountain
The three major rock groups, metamorphic rocks, igneous rocks, and sedimentary rocks, can all be identified around the Stone Mountain region. As mentioned before, Piedmont (the area surrounding the Stone Mountain) is comprised of mostly metamorphic rocks. The USGS website declared that Piedmont is also comprised of igneous rocks. The metamorphic and igneous rocks were derived from the re-crystallization of ancient (300-600 million years old) sediments that were once deeply buried and subjected to high temperatures and pressures. They were then re-exposed during a collision between Africa and North American continents about 300 million years ago.
The Georgia Piedmont
The Georgia Piedmont is situated between the coastal plain and the mountains in Georgia’s Stone Mountain region. It is a homely habitat for such animals as; opossums, squirrels, Canada geese, ducks, woodpeckers, blue jays, and owls. It is forestry that hosts trees like; pine trees, oak trees, and hickory trees.
The area surrounding the Georgia Piedmont consists of mostly moderate to high-grade metamorphic rocks, which includes; schists amphibolites, gneisses, and migmatites and igneous rocks like granite. Piedmont’s topography comprises rolling hills even though faulting, which caused the isolated granitic pluton to rise above Piedmont’s landscape and produce prominent features like Stone Mountain. In other words, the Piedmont region played a part in the creation of Stone Mountain through the faulting caused by consuming boundaries (pushing together) of plates in that area.
Resources in Stone Mountain
There is a variety of resources in the Stone Mountain region-some in abundance and others in scarcity. Oil and natural gas is one such example of resources in scarcity. On the other hand, abundant resources-there is an abundance of groundwater located in the coastal plains. Concerning the University of Georgia’s Department of Geology-the, the less porous rocks of Georgia’s other regions provide less groundwater. Still, the coastal plains’ aquifers dispense a surplus of groundwater for domestic consumption, industry, and agricultural irrigation.
The coastal plains are also hosted to one of the most significant and economic minerals known as kaolin, a clay-rich rock mined near the Fall Line. This rock holds substantial economic value in the region. Kaolinite, which the dominant mineral of kaolin, is used in various industries, from paper to pharmaceuticals.
Secondly, the Piedmont mineral resources include hard crushed stone, which is quarried by such companies like Vulcan Materials. In addition to that, Stone Mountain itself was mined for granite, which is probably the most abundant, used in various buildings. All the resources mentioned above play a vital role in the economy of Stone Mountain and Georgia’s surrounding region. Not only that, these resources aid in improving the quality of life of the inhabitants.
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- “Description of Stone Mountain”, (2011), Stone Mountain Entertainment, Retrieved from: http://stonemountain.com/description
- “Georgia Geology”, (2011), www.gly.uga.edu, retrieved from: http://www.gly.uga.edu/default.php?PK=0&iPage=5#Links
- Gore P. “Geologic History of Georgia: overview”, (Jul 1, 2006), georgiaencyclopedia.org, retrieved from: http://www.georgiaencyclopedia.org/nge/Article.jsp?id=h-3510
- “Gneiss Rock”, (2011), Encyclopedia Britannica, Retrieved from: http://www.britannica.com/EBchecked/topic/236276/gneiss
- Worthy, L “Stone Mountain Natural History”, (2011), ngeorgia.com, Retrieved from: http://ngeorgia.com/ang/Stone_Mountain_Natural_History