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A Historical Look Into The Smokies
ABSTRACT
The Great Smokey Mountains are home to over 500,000 acres of beautiful scenic peaks and valleys. The topographic features reflect the history of the mountains. The character and landscape of the Smoky Mountains are a result of the rocks and geologic processes that formed these mountains.
INTRODUCTION
About 470 million years ago, the motion of the crustal plates changed, and the continents began to move toward each other. Eventually, about 270 million years ago, the continents ancestral to North America and Africa collided. Huge masses of rock were pushed west-ward along the margin of North America and piled up to form the mountains that we know as the Appalachians.The Great Smokey Mountain also known as the “Smokies” are inside the Blue Ridge Mountains, part of the Southern Appalacians. The blue haze which resembles smoke clings over the mountainside which gives the mountain its name. The wispy fog that hangs over the Smoky Mountains comes from rain and evaporation from trees. On the high peaks of the Smokies, an average of 85 inches of rain falls each year, qualifying these upper elevation areas as temperate rain forests. The Smokies are located along the border of Tennessee and North Carolina. The Great Smokey National Park protects one of the most diverse ecosystems on the planets. It is home to more than 4,000 species of plants, 130 trees, 65 mammals, and 230 birds. It is the most visited National Park in the United States with over nine millions visitors each year. Due to faulting, folding, fracturing, and weathering the Great Smokey Mountains National Park has a very complex geology and formation.
ROCKS
Precambrian age rocks, the oldest rocks, are believed to be the majority of the rocks in the Smokies. Igneous, Sedimentary, and Metamorphic rocks all occur in the Smokies, although the majority of the rocks are metamorphosed sedimentary. The degree of metamorphism varies, but is generally light to moderately metamorphosed, allowing for some sedimentary rock features to still be identified (layers of strata are often distinguishable). There are many minerals in the Park, but some of the most common are quartz, calcite, mica, pyrite limonite, feldspar, and kaolinite.The rocks in the Park range from over 1 billion to almost 350 million years old. These rocks originated in a sea or an ocean located between the two continental plates that would eventually collide. This ocean or sea was probably a moderately shallow sea platform, as shown by such rock types in the Smokies as limestones, sandstones, and shales.Since the formation of the Smokies 200 million years ago, the rock strata has been weathered by rain, sleet, snow, ice, heat, and wind. Shale, slate, phyllite, and limestone have been eroded at a much faster rate than the sandstone, siltstone, quartzite, and various other rocks (mainly metamorphic). The majority of the bedrocks in the Park are divided into three groups: the metamorphic rocks from the Precambrian basement complex, the lightly metamorphosed sedimentary rocks of the Ocoee Super group of rocks in the late Precambrian era, and the sedimentary rocks of the Appalachian Ridge and Valley.
GEOLOGICAL PROCESS
The character and landscape of the Smoky Mountains are a result of the geologic processes that formed these mountains. The Smokies are round, but still rugged, mountains with few rock outcroppings, numerous stream drainages, and landslide scars. These topographic features reflect the ancient history of these mountains and the fact that they have been and continue to be shaped by the combined actions of thrust faults, uplifts, and erosion. Most of the rocks encountered in the park are of a sedimentary type, some of which have been metamorphosed to varying degrees. Sandstone, siltstone, conglomerates and slates are the most common types. Limestone, found in a few areas, primarily in Cades Cove, tells of the ancient proto-Atlantic Ocean that once covered this land. Late in the Precambrian era, (four billion to six hundred millions years ago) about 50,000 feet of sediments were deposited as the ocean encroached on the landmass. Extreme heat and pressure thrust rock shelves thousands of feet into the air. Streams and rivers flowed, allowing the flora and fauna to prosper while the razor-edged ridges were rounded to reveal the ecologically rich environment and smooth look of the Great Smokey Mountains. During the Mesozoic, the younger rock was eroded away, leaving the much older rock exposed. The series of ridges, valleys, and mountain crests developed during this time, as the mountains were being uplifted at the same rate they were eroded away. Due to the fluctuation of the climate in the Ice ages the erosion was expedited. During this time the Park's climate went from tropical to subtropical to temperate as the continent moved to more northerly latitudes. The Clingmans Dome is the highest peak in the Smokies, at an elevation of 6,643. Even today shaping of the Great Smokies continues as erosional forces are now dominent.
FORMATION
Many things have factored into the making of the Great Smokey Mountains, but most of the credit goes to two very related occurrences. These are the collision of two continental plates 200 million years ago, at the end of the Paleozoic era, and the many thrust faults located around the Great Smokies. The period of time while the continents were colliding is known as the Appalacian orogeny(meaning the formation of the Appalacian Mountains. During the Precambrian Era the proto-Atlantic Ocean was formed. Topographically, the ocean was a low area that eventually became the Appalachian geosyncline (a depositional basin of continental proportions that is filled with sediments over a large period of time). The Precambrian highlands, consisting of sandstones and quartzites, were eroded and washed into the ocean. As erosion lowered the land, the ocean began to spread and cover some of the sediments previously deposited. In the shallow marine environment, carbonate deposits (later to become mostly limestone) were laid down as the shells of dead invertebrates drifted to the bottom and accumulated. The proto-Atlantic Ocean filled in with sediments and became land that eventually turned into the Appalachian Mountains. During this time, the rock strata and ocean sediments from between these two colliding continents were crushed, broken, folded, and eventually faulted. The faulting occurred when the rock strata and sediments were being broken and shoved over each other. When this uplift occurred, the result was the formation of the Appalacian, Blue Ridge, and Great Smokey Mountains. When the colliding continents crushed the rock strata, large thrust faults occurred. The Great Smokey Fault is one of these faults. This fault has moved thousands of feet of late Precambrian rock up and over the younger Paleozoic rocks. This older, more resistant metamorphosed rock strata formed the bulk of the Smokies we see today.
CONCLUSION
Tectonic plates, sediment, ancient glaciers and unique weather patterns have all played a big part in creating the Smokies. By reading the rocks, and exploring geology we can trace it's incredible history. Today the Great Smokey Mountains National Park is an International Biosphere Reserve and a World Heritage Site.
REFERENCES
Wikipedia, 2007 The Great Smokey Mountains, http://www.en.wikipedia.com/wiki/TheGreatSmokeyMountains
http://www.americanparknetwork.com/parkinfo.sm/geology/index.html
http://www.nps.gov/archive/brca/Geodetect/Plate%20Tectonics/mountains.htm
