Five_Geological_Regions_of_Georgia

Five Geological Regions of Georgia Five Geological Regions of Georgia The history of Georgia’s geology can be traced back at least one billion years. Georgia’s geology was impacted by the formation and erosion of mountain ranges, intense climate changes, flooding by the sea on numerous occasions, and volcanic eruptions. The state can be divided into five regions based on their characteristic landforms, types and ages of rocks, and geologic structures. The five regions are the Piedmont, Blue Ridge, Valley and Ridge, Appalachian Plateau, and the Coastal Plains. All of these geologic regions extend into the surrounding states, but Georgia is the only state south of Virginia that has all of these regions. The oldest rocks in Georgia are found in the Piedmont and Blue Ridge regions, which run northeast to southwest through the center of the state. The rocks range in age from 1 to 1.3 billion years, dating them back to the Proterozoic Era. The two regions are composed mainly of metamorphic rocks and igneous rocks. Extremely high temperatures and pressures deep below the earth’s surface formed metamorphic rocks. The cooling and crystallization of molten magma formed igneous rocks. These regions also show signs of having been contorted, bent, and twisted by tremendous compressional forces within the earth’s crust numerous times. The Piedmont region has large faults that support these events, the main one being the Brevard Fault zone. The Piedmont region is also the largest region out of the five. The Blue Ridge contains the highest and largest group of mountains in the state. The Brasstown Bald is the highest out of all the mountains. The Cartersville fault separates the Piedmont region from the Valley and Ridge region. The Cartersville fault marks the place where Piedmont metamorphic rocks were shoved westward over sedimentary rock layers of the Valley and Ridge. This action was most likely due to the collision of Gondwan with North America near the end of the Paleozoic Era. The Valley and Ridge region and the Appalachian Plateau lie west of the Cartersville fault. The rocks of these regions are just as old as the ones in the Piedmont region, but they haven’t been subjected to the extreme heat and pressure as the ones in the Piedmont. The rocks here still show their original sedimentary textures, structures, and fossils. They occur as layers and consist mainly of sandstone, shale, limestone, and dolostone. In the Valley and Ridge region the layers have been bent into great folds that erode and forms the long winding ridges and valleys from which the area is named. The rocks in this area contain numerous fossils. Due to the fossils and rocks, geologists have concluded that the Valley and Ridge area was formed in ancient seas from flooding during the Paleozoic Era. The Appalachian Plateau is the smallest region on the state. It has sedimentary layers that are still horizontal due to not having been bent or twisted. In the lower elevations, these rocks are mainly limestone and dolostone similar to the ones in the Valley and Ridge region. As the elevation goes up, you begin to see sandstone, shale, and coal beds that date back to the Pennsylvania Era. The region is filled with Limestone Caves, Deep Canyons, and rock called the Tag Corner. It also has sandy mountains that run as long as 100 miles long. The Coastal Plain region is divided into two parts: the Inner Coastal Plain and the Outer Coastal Plain. The Coastal Plains are separated from the other regions by the Fall Line. The Fall Line divides the hard, crystalline rocks of the Piedmont and Blue Ridge area with the softer, more erodible layers of the Coastal Plains. The Fall Line is known for its many waterfalls and rapids, which are caused by the different characteristics of the rocks on either side of the line. Rivers can’t erode deeply into the hard rocks of the Piedmont, but they can erode the softer layers of the Coastal Plains. Rapids and waterfalls are formed as the erosion of these layers results in the streams’ channels becoming steeper along the Fall Line. The Coastal Plain has layers of sedimentary layers that are under formed and unaltered. The oldest layers are of Triassic, Jurassic, and Lower Cretaceous Eras. These layers are not visible due to lying deeply beneath younger sedimentary layers. The layers were formed during the time when North America began to break away from the supercontinent. The oldest rocks exposed at the surface are dated from the Upper Cretaceous Era. They are mainly composed of sandstone, shale, and marls containing well-preserved fossils. These fossils show that these layers were formed in a coastal setting when sea level was higher. Most of the layers in the Coastal Plains formed during the Paleogene Period. Georgia features some of the most varied and intriguing terrain in eastern North America. Each of the five regions is made up with its own look, rock types, and history that allows for studies into Georgia’s historic geology. References Gore, P., & Witherspoon, W. (2013). Roadside geology of Georgia. Missoula, Mt: Mountain Press Publishing Company. The geology of Georgia. (n.d.). Retrieved from http://www.gly.uga.edu/railsback/GAGeology.html