Stone Mountain
Stone Mountain near Stone Mountain, Georgia, is a quartz monzonite dome monadnock and the site of Stone Mountain Park owned by the state but managed by Norcross-based Herschend Family Entertainment. At its summit, the elevation is 1,686 feet (514 m) above sea level and 825 feet (251 m) above the surrounding area. Stone Mountain is well known for not only its geology, but also the enormous rock relief on its north face, the largest bas-relief in the world. The carving depicts three Confederate figures, Jefferson Davis, Robert E. Lee, and Stonewall Jackson, and is the subject of widespread controversy as well as being a representation of southern white cultural pride and an artistic monument.
Stone Mountain was once owned by the Venable Brothers, "as a memorial to the Confederacy." Stone Mountain Park officially opened on April 14, 1965 – 100 years to the day after Lincoln's assassination, although the park had already been in use for a few years. By 2017, it was considered the most visited destination in the state of Georgia.
Stone Mountain is more than 5 miles (8 km) in circumference at its base. The summit of the mountain can be reached by a walk-up trail on the west side of the mountain or by the Skyride aerial tram.
Stone Mountain is a pluton, a type of igneous intrusion. Primarily composed of quartz monzonite, the dome of Stone Mountain was formed during the formation of the Blue Ridge Mountains around 300–350 million years ago (during the Carboniferous period), part of the Appalachian Mountains. It formed as a result of the upwelling of magma from within the Earth's crust. This magma solidified to form granite within the crust five to ten miles below the surface.
The Stone Mountain pluton continues underground 9 miles (14 km) at its longest point into Gwinnett County. Numerous reference books and Georgia literature have dubbed Stone Mountain as "the largest exposed piece of granite in the world". This misconception is most likely a result of misrepresentation by granite companies and early park administration. Stone Mountain, though often called a pink granite dome, actually ranges in composition from quartz monzonite to granite and granodiorite.
The minerals within the rock include quartz, plagioclase feldspar, microcline, and muscovite, with smaller amounts of biotite and tourmaline. The tourmaline is mostly black in color, and the majority of it exists as optically continuous skeletal crystals, but much larger, euhedral pegmatitic tourmaline crystals can also be found in the mountain's numerous, cross-cutting felsic dikes. Embedded in the granite are xenoliths or pieces of foreign rocks entrained in the magma.
The granite intruded into the metamorphic rocks of the Piedmont region during the last stages of the Alleghenian Orogeny, which was the time when North America and North Africa collided. Over time, erosion eventually exposed the present mountain of more resistant igneous rock. This intrusion of granite also gave rise to Panola Mountain and Arabia Mountain, both in DeKalb County, smaller outcroppings farther south of Stone Mountain.
Reference
ليست هناك تعليقات:
إرسال تعليق