GUIDE TO GEOLOGIC POINTS OF INTEREST
ALONG INTERSTATE 26
North Carolina-South Carolina
State Line to Asheville
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 26 between the North Carolina-South Carolina state line and Asheville. We encourage you to exit the Interstate when you can to stop, look, and listen to the sights and sounds that make North Carolina a truly natural wonder.
USE OF THE GUIDE
The guide is keyed to the Interstate mileposts which are small, green signs with white numerals located on the shoulder of the road. This guide is designed to be used by travelers going west and north on I-26 from the Welcome Center near the South Carolina line near mile 36.5. Travelers going east on I-26 starting near Asheville at milepost 0 should read the guide in reverse order.
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.
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 the 1990s, 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 over $90,000.
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
This road guide is intended to make your drive on Interstate 26 more interesting by describing some of the features along the route as seen through the eyes of a geologist.
View points mentioned in this brochure are keyed to the Interstate mileposts, which are small green signs with white mileage numbers located along the road shoulder.
In North Carolina, Interstate Route 26 runs from the North Carolina-South Carolina border northwest for about 40 miles to Asheville. The route crosses parts of two major topographic provinces of North America, the Piedmont Province and the Blue Ridge Province.
A topographic province, such as the Piedmont or Blue Ridge, is a large area or region characterized by similar landscape features.
The Piedmont is a plateau-like region with low, rounded, gently rolling hills and sinuous streams, some with broad flood plains. This region slopes gently seaward away from the mountains.
The Piedmont's western limit is the base of the Blue Ridge Mountains. Along I-26, this abrupt boundary has an elevation of about 1,150 feet. A short distance west of this boundary, some of the easternmost peaks and ridges of the Blue Ridge reach elevations well over 3,000 feet.
The area between the Piedmont and these eastern peaks of the Blue Ridge is the Blue Ridge Front. Its extremely rugged terrain includes very steep slopes, deep valleys, rock cliffs and streams with waterfalls and rapids. These features offer many striking, picturesque views.
The Blue Ridge Province consists of individual mountain ranges separated by valleys and occasionally by wider, relatively flat basin-like areas. The highest mountain peaks in the eastern United States are in the North Carolina portion of the Blue Ridge. Mt. Mitchell, the highest peak of them all with an elevation of 6,684 feet, is located in the Black Mountain Range about 20 miles northeast of Asheville.
In the Blue Ridge Province, nearly all the cities and most of the population are in the valleys and basins. The smaller valleys are called "coves." Until recent years, many isolated coves were sites of nearly self-sufficient communities inhabited by only a few families where old traditional customs and crafts were maintained and handed down through the generations.
The Asheville Basin is the largest intermountain basin in the Blue Ridge Province. It provides fairly level terrain for several of the main routes through the Blue Ridge including Interstates 26 and 40, U.S. Highways 25, 64, and 70, and a main line of the Norfolk-Southern Railway.
39.8 Border between North Carolina and South Carolina.
36.5 Welcome Center (access from westbound lanes only). 34.6 Rocks exposed in these road cuts are similar to those underlying extensive areas of the Piedmont. These outcrops are dominated by dark-colored, coarsely banded metamorphic rock. Metamorphic means changed by heat and pressure. Within this coarsely banded metamorphic rock are conspicuous masses of white quartz and feldspar up to several feet in size. There are also veins of granite cutting across the banded rocks. The quartz and feldspar masses and granite veins show that there was molten rock activity here long ago. Molten means melted; in this case, rocks that have been made liquid by heat. These rocks probably formed six or more miles beneath the Earth's surface. Over the eons, they were gradually uplifted while the overlying rocks were being worn away by erosion 31
Interstate 26 begins to ascend the Blue Ridge Front toward Howard Gap, elevation about 1,900 feet. Nearly 1,000 feet below the gap is the rolling topography of the Piedmont Plateau.
During construction of I-26 in the late 1960s and 1970s, work on the section from Howard Gap to the base of the Blue Ridge was disrupted by numerous landslides along the slopes of Tryon Peak and Miller Mountain. Special engineering design, remedial work, and careful construction were necessary before the steep slopes were successfully stabilized so that the road could be completed. One of the most important parts of this work was to control the water in the soil and earth. This was done mainly by installing an extensive series of underground drain pipes into the hillside for several miles along the road.
A stone monument placed in the gap just north of the Interstate records a bit of history from the time the Blue Ridge marked the western frontier of the nation. The plaque on the monument reads: "To commemorate the Battle of Round Mountain in which Captain Thomas Howard and his brave followers with the faithful Indian guide Skyuka defeated the Cherokee Nation, 1776." Round Mountain is the hill immediately south of the Interstate across the road from the monument.
28 Directly east as you travel toward South Carolina is Tryon Peak, elevation 3,234 feet, one of the most noticeable peaks along the Blue Ridge Front. 24.8 Bridge across the gorge of the Green River. Deep, narrow gorges such as this have resulted from rapid erosion by streams cascading down the Blue Ridge Front onto the lower Piedmont. Erosion has been active for tens of millions of years and is responsible for the very rough terrain of the Blue Ridge Front. 22.5 Location of the Eastern Continental Divide, elevation 2,130 feet. Streams west of the divide, such as the French Broad River, flow to the Mississippi River and the Gulf of Mexico; those east of the divide (such as the Green River, mile 24.8) flow eastward to the Atlantic Ocean. 20 Apple orchards may be seen here and at several other places along the route. In this portion of the Blue Ridge, apples are an important crop. In the Piedmont, at lower elevations where the weather is generally warmer, peach orchards flourish. 18 A large quarry is visible about half a mile northeast of the Interstate. The stone in the quarry, and for many miles around, is a type of granite. Many years ago, several other quarries in the vicinity produced blocks of stone that were shaped into monuments and curb stones. At present, the stone from this quarry is crushed and used mainly in concrete and for road and building construction. 10.5
The wide flat valley is underlain by an unusual rock called mylonite. The characteristic feature of mylonite is its texture; the component mineral grains are crushed and appear smeared out. This distinctive texture is produced by movement or shearing of one part of the Earth's crust again an adjoining part. Movement of this type is called faulting, and the surface or zone within the Earth along which the movement occurs is called a fault or fault zone. The fault zone underlying this valley is named the Brevard Fault Zone. It has been traced for several hundred miles from Alabama well into North Carolina. Studies of the rock in the zone demonstrate that most, if not all, movement ceased at least 200 million years ago. The most active period of movement is estimated to have been about 350 million years ago.
The present-day valley exists because the mylonite along the Brevard Fault Zone is less resistant to erosion than the rock on either side of the zone.
The Interstate crosses the French Broad River and at mile 3.5. From about mile 5 to mile 11, the road parallels the river and, in places, lies in its flood plain. The river flows north and northwestward through the Blue Ridge. Near Knoxville, Tennessee, about 165 miles downstream from this area, the French Broad River merges with the Holston River to form the Tennessee River. The Tennessee River ultimately drains into the Mississippi which flows into the Gulf of Mexico.
The French Broad River was named by the early settlers and explorers for the fact that this was the first large, or "broad," river they encountered that flowed away from the original British colonies and into the French-owned lands of the continent's interior.
5 The Blue Ridge Parkway crosses I-26 at this point (access to the Parkway is via N.C. 191 at Exit 2). The Blue Ridge Parkway provides a scenic and leisurely route through much of the high mountain area of the southern Appalachians. 0 Interstate 26 ends about 4 miles southwest of Asheville at the junction of I-26, I-240, and I-40. This major interchange is partly located on an old river flood plain.