Smoky Mountains Visitors Guide

 

The Smoky Mointains Vistors Guide

 

Geology


As part of the Unaka Range a sub-range in the Appalachian chain. The building of the smoky mountains began more than a billion years ago. The Appalachian Mountains and the Blue Ridge Mountains are among the oldest on earth. These mountainous ranges are comprised of sediments of several thousand feet. That is, they were formed by accumulations of soil, silt, sand, and gravel deposited into a huge shallow sea. Over millions of years, more and more sediments were deposited, becoming layers of hard rock some nine miles or more thick. It was the collision of continental plates, which caused the earth to fold and climb above itself and rainfall that molded the earth's surface of the Smokies. Over time this rock was turned into a hard crystalline mass. 

The Ocoee series dates back about 600 million years when the rock hardened and then solidified. From 450 to 250 million years ago faulting, heat and pressure and more faulting, caused the mountain tops to rise above sea level. At one time the smoky mountains could have been higher than the rocky mountains. To this day, there are four major faults in the park - Great smoky, Gatlinburg, Greenbrier, and Oconaluftee. An entire belt of folded and faulted rocks extends over 2,000 miles from what is now Maine to Georgia and is known collectively as the Appalachian Mountains. The Great Smoky Mountains are but a small portion of that range.

Over 500,000 years ago, glaciers pushed down from the north cutting through the mountain rock and creating additional change the following and freezing of the glacier over the mountainous regions created rock beds by contracting and expanding the rock masses, cracking them into smaller pieces. This is evident by observing large boulders that are seen in the stream beds. Of course once the glaciers melted and retreated north, boulder creation stopped. Now the great smoky mountains that we see today, are products of these glaciers, plus wind, and water, eroding and cutting through the rock created the valley's and streams.

There are basically three types of rocks in the Smokies, sedimentary, igneous and metamorphic. These rocks are over 1 billion years old and are composed of gneiss, schist, (metamorphic rocks) and some granite (igneous rocks).

These basement rocks are so named because they form the foundation under the mountains upon which all the other rocks have been deposited. These rocks are only exposed in the southern and eastern portions of the park (North Carolina side), and in other areas of the mountains outside of the park.

Precambrian bedrock can also be seen in some places above younger Paleozoic rocks like, Cades Cove, Tuckaleechee and Wears Cove, which are dominated by Paleozoic limestone. But the  dominant rock type of the great smoky mountains is metamorphosed sedimentary rock, visible in places at Walden creek, Great smoky, and Snowbird, these are the three main groups of the Ocoee super group. Which are divided again into 13 formations. The Thunderhead and Anakeesta Formations are the most common rocks in the park. Along the northwest of the Great Smoky Mountains are visible evidence of a segment of unknown crust that found its way to the American Continent billions of years ago. Shale, limestone and sandstone are some of the youngest rock types that can be seen at, White oak Sink, Cades Cove and the Foothills Pathways.


Tour: Mile Markers (North to South) Cross-referenced to timeline.

Mile 217.3 - Cumberland Knob, Late Proterozoic (750 MYA), Alligator Back thinly-foliated

Mile 218.6 - Fox Hunters Paradise, Brevard fault, broke through 300 MYA during the Alleghenian orogeny

Mile 230.1 - Little Glade Millpond Overlook, Late Proterozoic (750 MYA) Alligator Back rocks showing "pinstripes" of muscovite and biotite

Mile 242.3 - Alligator Back Overlook, Late Proterozoic , (750 MYA) Alligator Back finely-laminated layers of "pinstripe" gneiss and schist

Mile 284.6 - Grenville-age (1 BYA) biotite granitic gneiss in contact with the Late Proterozoic (750 MYA) Ashe Metamorphic rocks

Mile 281.9 - Late Proterozoic (750 MYA), Alligator Back and Ashe Metamorphic Suite contact

Mile 289.9 - Yadkin Valley Overlook, Yadkin River changes direction because of the Brevard fault. The fault broke through 300 million years ago during the Alleghenian orogeny

Mile 290.4 - Thunder Hill Overlook, Grenville (1 BYA) Blowing Rock augen gneiss

Mile 292.8 - Contact between Late Proterozoic (750 MYA) Grandfather Mountain Formation and Grenville-age (1 BYA) Blowing Rock gneiss

Mile 302.1 - Wilson Creek Valley Overlook, Late Proterozoic (750 MYA) Grandfather Mountain Formation showing green metadiabase with actinolite and chlorite.

Mile 315.0 - Late Proterozoic (750 MYA) Grandfather Mountain Formation and Cambrian (550 MYA) Chillowee quartzite

Mile 316.14 - Linville Falls Visitor Center, Cambrian (550 MYA) Chillowee metasandstone and Grenville-age (1 BYA) biotitic granitic gneiss.

Mile 320.8 - Chestoa View, Grandfather Mountain Window, Cambrian (550 MYA)Chilhowee Quartzite and dolomite inside the window; Grenville (1 BYA)Blowing Rock gneiss as the frame.

Mile 323.0 - Bear Den Overlook, view of Mt. Mitchell made of Late Proterozoic (750 MYA) Ashe Metamorphic Suite; also, there is evidence of the Taconic orogeny (550 - 450 MYA) in migmatic rocks.

Mile 330.9 - Museum of North Carolina Minerals, Exhibits many rocks and minerals on the drive, including the Taconic-age (550-450 MYA) Murphy marble.

Mile 232.5 - Stone Mountain Overlook, view of Stone Mountain, an igneous plug of Devonian-age, Acadian orogeny (400-350 MYA)

Mile 352.4 - Bald Knob Ridge Overlook, Late Proterozoic (750 MYA) Ashe Metamorphic Suite

Mile 364.1 - Craggy Dome Overlook, Late Proterozoic (750 MYA) Ashe Metamorphic Suite, garnets and kyanite index minerals

Mile 413.2 - Pounding Mill Overlook, Brevard fault zone, broke through 300 MYA during the Alleghenian orogeny

Mile 440.8 - Taconic (550-450 MYA) Holland fault showing Late Proterozoic (750 MYA) Ashe Metamorphic rocks and Grenville-age (1 BYA) basement rocks

Mile 445.2 - Mount Lyn Lowry Overlook, Middle Proterozoic (1 BYA) olivine - Balsam Gap olivine mine

Mile 446 - Woodfin Valley Overlook, Grenville-age (1 BYA) highly-folded banded biotite gneiss. These are the oldest rocks on the Blue Ridge Parkway.

Mile 446.2 - Taconic (550 - 450 MYA) Hayesville fault showing Late Proterozoic (750 MYA) Great Smoky Group metagraywacke and Grenville-age (1 BYA) biotite gneiss

Mile 450.2 - Yellow Face Overlook, Late Proterozoic (750 MYA) Great Smoky Group

Mile 451.2 - Waterrock Knob Overlook, view of Roan Mountain, 1.3 billion years old. This mountain is underlain by the oldest rocks in North Carolina.

Mile 467.4 - Ballhoot Scar Overlook, Late Proterozoic (750 MYA) Great Smoky Group and Snowbird Group

Mile 468.7 - Taconic (550 - 450 MYA) Greenbrier fault showing Late Proterozoic (750 MYA) Snowbird Group rocks and Grenville-age (1 BYA) mylonitic biotite granitic gneiss.

 

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