GUIDE TO GEOLOGIC POINTS OF INTEREST
ALONG INTERSTATE 40
State Line to Winston-Salem
WELCOME TO NORTH CAROLINA
From the Blue Ridge and Great Smoky Mountains to the white, sandy beaches of the Atlantic Ocean, the "Tar Heel" state has a variety of natural resources awaiting the traveler.
We hope this guide will be useful in identifying some interesting geologic features as you travel Interstate 40 between the North Carolina-Tennessee state line and Winston-Salem. We encourage you to exit the Interstate when you can and stop, look, and listen to the sights and sounds that make North Carolina a truly natural wonder.
USE OF THE GUIDE
This guide is keyed to the Interstate mileposts, which are small green signs with white mileage numbers located on the shoulder of the road. This guide is designed to be used by travelers going east on I-40 from the Welcome Center near the Tennessee state line. Travelers going west can use this guide by reversing left and right and using the alternate mileage figures. However, some features on hill slopes facing eastbound traffic may not be visible to westbound traffic. For orientation purposes, the Welcome Center is between milepost 10 and milepost 11.
Stopping is not permitted on the Interstate system, except for emergencies. However, stops are not necessary to enjoy this guide, as only features visible from a moving car are included. While driving and viewing, please observe traffic laws and safety rules.
Each point of interest on the map has a number that corresponds to a numbered explanation in the text. The explanation gives a detailed location and a description of the feature. If you read the description several minutes before you reach the feature described, you can enjoy an uninterrupted view as you pass.
A GLANCE AT THE GEOLOGY OF NORTH CAROLINA
North Carolina has a long and complex geologic history. Although much remains to be learned, a general understanding of regional geological relationships has emerged. The state is described in terms of geological belts; that is, areas with similar rock types and geologic history.
Blue Ridge Belt: This mountainous region consists of rocks that are from over one billion to about one-half billion years old. This complex mixture of granite, gneiss, schist, volcanic rock, and sedimentary rock has repeatedly been squeezed, fractured, faulted, and twisted into folds. The Blue Ridge Belt is well known for its deposits of feldspar, mica, and quartz, which are basic materials used in the ceramic, paint, and electronic industries.
Inner Piedmont Belt: The Inner Piedmont Belt is the most intensely deformed and metamorphosed segment of the Piedmont. These rocks are about 750 to 500 million years old.
Kings Mountain Belt: This belt consists of less intensely deformed and metamorphosed volcanic-sedimentary rocks. World-famous lithium deposits are mined here. Lithium is used in ceramics, aluminum production, greases, and medicine.
Milton Belt: The Milton Belt consists of gneiss, schist, and metamorphosed igneous rock.
Charlotte Belt: This belt consists mostly of igneous rocks (rocks crystallized from molten rock), such as granite, diorite, and gabbro. These are 500 to 300 million years old.
Carolina Slate Belt: The Carolina Slate Belt consists of heated and deformed volcanic rocks. It was the site of a series of oceanic volcanic islands about 650 to 550 million years ago. This belt led the nation in gold production before the California Gold Rush of 1849, and is well known for its many abandoned gold mines and prospects. In recent decades, only minor gold mining has taken place, but mining companies continue to show interest in the area.
Triassic Basins: These basins consist of sedimentary rocks formed about 200 to 190 million years ago by streams carrying mud, silt, sand, and gravel from adjacent highlands into rift valleys similar to those of present-day Africa. The shales are mined for brick clay. North Carolina leads the nation in brick production.
Raleigh Belt: The Raleigh Belt contains granite, gneiss, and schist. In the 19th century, there were a number of small building-stone quarries in this region, but today the predominant mineral product is crushed stone used in construction. In the1990s, the value of crushed stone produced in North Carolina exceeded 450 million dollars per year. For all mineral resources mined in North Carolina, the average yearly return per acre devoted to mining is more than $90,000.
Eastern Slate Belt: This belt contains slightly metamorphosed volcanic and sedimentary rock similar to that of the Carolina Slate Belt.
Coastal Plain: A generally eastward-thickening wedge of mostly marine sedimentary rocks, the Coastal Plain covers about 44 percent of the land area of the state. The most common rock types are muddy sandstone and mudstone, although a significant body of limestone occurs in the southeastern segment. In the Coastal Plain, geology is best understood from studying well data. The state's most valuable mineral resource, phosphate ¿ an important component of fertilizer ¿ is mined in the Coastal Plain.
FOR MORE INFORMATION
For more information on the geology of North Carolina, please contact the North Carolina
Geological Survey at:1612 Mail Service CenterOther state agencies with natural resource information include:
Raleigh, NC 27611-1612
http://www.geology.enr.state.nc.us¿ Division of Forest Resources
1616 Mail Service Center
Raleigh, NC 27699-1616
¿ Division of Soil & Water Conservation
1614 Mail Service Center
Raleigh, NC 27699-1616
¿ Division of Parks & Recreation
1615 Mail Service Center
Raleigh, NC 27699-1615
POINTS OF INTEREST
1 Greenbrier Fault is three-tenth of a mile east of milepost 11 (0.7 miles west of milepost 12) on the left side of the road. This feature is an almost vertical gash between light-colored quartzite on one side and darker greenstone on the other side. A fault is a zone along which there has been displacement of the rocks on one side of the zone relative to the rocks on the other side. At this road cut, the Greenbrier Fault is nearly vertical. In most places, it is an inclined zone with the southeast side down. The rocks on top slid northwestward up and over the rocks on the bottom. Movement along faults takes place in short bursts of a few inches or a few feet at a time and not along all portions of a fault at the same time. It may take millions of years to achieve the total displacement. The Greenbrier Fault is estimated to have been active approximately 500 million years ago.
2 For a side trip to commercial gemstone mines, take the U.S. 276 exit east of milepost 20 (west of milepost 21) on the right side of the road. Drive south on U.S. 276 for 6 miles to U.S. 19, and take U.S. 19 for 20 miles to Maggie Valley and beyond to Cherokee. From Cherokee, you can take U.S. 441 for 30 miles to Franklin, North Carolina, and try your luck at gemstone mining at any of the numerous commercial mines in that area. 3 Coleman Gap, a deep road cut into black and white "marble cake," swirly banded rock, is about four-tenths of a mile east of milepost 22 (about 0.6 miles west of milepost 23), on both sides of road. It is clearly visible from your car and is an excellent example of one type of gneiss. Gneiss, one of the more common rock types in the Appalachians, is a type of metamorphic rock formed by deformation of rock at high temperatures and pressures, such as those found several miles below the Earth's surface. The banded rock in Coleman Gap is the result of differentiation of dark and light minerals into separate bands. 4 The gently rolling "plain" of the French Broad River is in the distance to the east at milepost 36. Asheville sits in this valley. This lower, smoother surface surrounded by higher, more rugged mountains was formed in the past when the forces of erosion broadened and flattened the valley floor. At Asheville, the river occupies a 200-foot-deep gorge cut into the flatter surface you are viewing. This entrenchment of the river was caused by uplift of the entire area after the "plain" was formed.
This feature, along with many others, suggests that there have been repeated cycles of uplift and erosion along the mountain chain. The total result of these cycles is the carving of the land into the valleys and ridges we call the Appalachian Mountains.
5 Biltmore Estate is just east of the overpass at milepost 47. As you drive under the overpass, the Biltmore Mansion is to the right in the middle distance. One part of Biltmore ¿ George Washington Vanderbilt's estate ¿ is a lush, productive forest that was created by forester Gifford Pinchot.
In 1892, Vanderbilt hired Pinchot to develop a forest plan for his beloved Biltmore. Pinchot, one of the most influential figures in the early conservation movement, introduced selective logging, the removal of defective trees, and planned reproduction for Biltmore's forests. His foresight shaped the lush forest we find today.
Pinchot left Biltmore in 1898, to become the head of the agency that is now called the United States Forest Service. Biltmore's next forester was Carl A. Schenck, a German "Forstmeister" (head forester). Schenck opened the Biltmore Forestry School, the first forestry school in America.
6 The North Fork of the Swannanoa River valley is between milepost 60 and 61, to the left of the road. This is the long valley, approximately six-tenths of a mile east of milepost 60, to the left and at a right angle to the highway. Stockpiles of mined alluvial sand and gravel can be seen at the mouth of the valley. Sand and gravel are deposited when fast-flowing mountain and upland streams decrease their velocity upon entering less rugged territory; or, as in the Swannanoa River valley, the river connects with another stream in a broader, more gently sloping valley. Since 1990, North Carolina sand and gravel producers have averaged over 77 million dollars in sand and gravel production per year, or more than 2,000 pounds per year for every person in the state. In the Piedmont and mountain portions of North Carolina, these alluvial deposits are the only source of natural sand and gravel. 7 The top of the Blue Ridge Front is just east of milepost 67 (the bottom of the Blue Ridge Front is just west of milepost 72). The grade down the Blue Ridge Front covers a distance of 4.8 miles. At the top of the grade is the Eastern Continental Divide, and west of this point all streams drain into the Mississippi River which drains into the Gulf of Mexico. East of the Eastern Continental Divide rivers empty into the Atlantic Ocean.
Topographically, the Blue Ridge Front represents a sharp break between the mountains and the Piedmont. The change in elevation along the 4.8-mile-long grade is approximately 1,400 feet. The Blue Ridge Front represents the contact between rocks of the Blue Ridge Belt and rocks of the Inner Piedmont Belt. At the top of the grade, the road cuts are in light-colored metamorphosed sandstone (quartzite), but at the bottom of the grade the units are darker colored gneisses that have been deformed and sheared. At the base of the grade, the highway will cross the Brevard Fault Zone, one of eastern North America's better known fault zones. The fault zone is ancient, perhaps first activated as much as one-half billion years ago, but there is no evidence to suggest that it has been significantly active during historical time.
Relax and enjoy your descent with the knowledge that the road you are traveling on replaced one that had over 20 hairpin curves.
8 Linville Gorge is at milepost 90, to the left of the road. Look for a brief, but spectacular view (in clear weather) of Shortoff Mountain and, about 16 miles from Interstate 40, Hawksbill Mountain. To the left of these mountains is Linville Gorge. The gorge is considered by some to be the most rugged wilderness area in the eastern United States. 9 The South Mountains are at milepost 104 to the right side of the road, and ahead in the east. The northern terminus of South Mountains looms ahead, and the range stretches away to the south. The South Mountains were formed as the result of more resistant rock layers withstanding erosion better than adjacent less resistant layers. The South Mountains are considered to be in a different geologic belt than the Blue Ridge Mountains.
Around the turn of the century, extensive prospecting and mining for gold and monazite took place along the streams in this range and south of it. Monazite is a phosphate mineral with rare earth metals and thorium in its chemical makeup. At the time it was being mined in North Carolina, it was used to make mantles for gas lights. In the 1890s, four diamonds were found in the streams of the western Piedmont. Some geologists believe the source of these diamonds might be hidden in the South Mountains, but so far it has not been found.
The South Mountains are the site of South Mountains State Park. The park, an excellent example of upper Piedmont ecology, is located thirteen miles south of Morganton on SR 1904. It is a popular site for picnicking, fishing, hiking, horseback riding, and backpacking. There are 12 miles of trout stream in the park, as well as a number of nature trails. The 4.1-mile Falls Trail allows visitors to view the 70-foot High Shoals waterfall (illustrated on the front of this brochure). The park is open all year from 8:00 am to sunset. Admission is free.
As you drive along the edge of the South Mountains, think about the uses of these forests. Forests aren't only scenery, they are also the base of an industry with many products. What do soap, waxes, plastics, photo film, chewing gum, and even the rayon shirt or blouse you may be wearing have in common? They are a few of the many thousands of items that come from trees in our forests.
This area's hardwood forests provide an important source of timber for these products. In fact, forestry-related products are the basis for North Carolina's second largest industry.
10 Some examples of good conservation practice can be observed between milepost 133 and 134 on the left side of the road. Clearly visible are examples of field strip-cropping, grassed water ways, and critical area stabilization.
Conservation practices are designed to help save our soil resources. Soil, one of our most precious natural resources, is not renewable over the short term. Depending on how one defines soil, 30 to more than 10,000 years may be required to form one inch of topsoil.
Soil is lost through erosion, a natural process that is accelerated when the soil is disturbed. In North Carolina, the erosion rate is higher than the soil formation process, but this condition can be reversed through good conservation practices.
11 Just east of milepost 160 to the right of the road, another conservation practice ¿ parallel diversion with waterways ¿ can be observed. Like the previous points of interest, this is an example of a "best management practice" recommended by a Soil and Water Conservation District. In North Carolina, the Districts, under the direction of the N.C. Division of Soil and Water Conservation, provide free technical assistance through the Federal Soil Conservation Service and county commissioners to solve erosion problems.
As you drive along, you may see other examples of best management practices. These practices are expensive for farmers to install, and they represent a long-term commitment by farmers to save our resources.