This EarthCache is available from Sunrise to Sunset each day.
At the posted coordinates you will observe a geological feature called the fall line as the Oconee River flows from the Georgia Piedmont to the Coastal Plain. In this Earthcache you will learn about the formation of the fall line in Georgia.
Source: Photo by Alan Cressler via Flickr
Logging Requirements
- As you observe the river, what specific geological features tell you that a fall line exists here?
- From the posted coordinates you will observe the remains of a building. This building served as the first hydro-electric plant for the City of Milledgeville. Why do you think this location was chosen?
- In your log, please post a photo of yourself or a personal item at the posted coordinates.
Please send your answers to the above questions within 14 days of logging your find. Failure to send answers and post a photo within this time frame will result in your log being deleted.
Geography of the River
The Oconee River is a 220-mile-long Georgia river originating in Hall County at the foot of the Appalachian Mountains. It ends where it joins the Ocmulgee River to form the Altamaha River at the intersection of Jeff Davis, Montgomery, and Wheeler Counties. South of Athens, two forks, the Middle Oconee River and North Oconee River, flow for 55–65 miles upstream, converging to form the Oconee River.
North of Milledgeville The Oconee River passes through the Oconee National Forest into Lake Oconee, near Madison and Greensboro. From Lake Oconee, the river travels to Lake Sinclair north of Milledgeville. Both Lake Oconee and Lake Sinclair are man made lakes. Below Sinclair Dam the river flows freely, with the exception of one abandoned diversion dam near Milledgeville, for about 143 miles to its confluence with the Ocmulgee.
The Oconee River Basin drains a total of 5,330 square miles. The Upper Oconee contains 10,973 acres of lakes. The river basin provides drinking water for about than 281,614 people in the state of Georgia, and irrigates nearly 20,000 acres of farmland.
Source: Anna Baynes (UGA River Basin Center)
Oconee River
The Oconee River derives its name from the Oconee, the Muskogean speaking Creek people who lived in central Georgia. The Oconee lived in present-day Baldwin County in a settlement known as Oconee Old Town. “Oconee” is an anglicized form of the word Okvni meaning “born from water.”
The Oconee River played a significant role in the early history of Georgia, particularly as a state boundary. Until 1805, the Oconee River served as the national boundary between the United States and the lands of the Creek Indian peoples. If you were standing at the posted coordinates in 1800, you would be standing in Creek land and looking across the river at the United States and the state of Georgia.
The Oconee War was a significant military conflict that took place in the 1780s and 1790s between American settlers and the Creek Indians, particularly the Oconee tribe, in the state of Georgia. This conflict arose from the increasing tensions and competition for land as more Americans moved into Oconee territory, which lay between the Apalachee and North Oconee rivers.
The Treaty of New York signed on behalf of the Creek nation of Indians was the first treaty negotiated after ratification of the U.S. Constitution. It established the Altamaha and Oconee rivers as the boundary between Creek lands and the United States. This boundary was established to demarcate the limits of European settlement and to protect the territories of the Creek Indians. A chain of forts were established along the eastern bank of the Oconee River to monitor and control the movement of settlers and to maintain the boundary.
This location of this earthcache, the Oconee River Greenway Park, was also the site of a brick factory. J. W. McMillan, born in Glasgow, Scotland in 1850, established the Milledgeville Brick Works in the 1880s, which operated until the early 1940s. It had six kilns and could produce up to 2,000 bricks per day. Buildings constructed with McMillan's bricks include the First Presbyterian Church on South Wayne Street, the original barracks at Georgia Military College, the Old Baldwin County Courthouse (1886), and the Jones Building for Central State Hospital.
The Fall Line
Georgia’s fall line is a geologic boundary marking the prehistoric shoreline of the Atlantic Ocean as well as the division between the Piedmont and Coastal Plain regions of the state. Rivers below this line tend to be slower moving, larger, and easier to navigate than those above the line. The fall line is characterized by a series of waterfalls and rapids where the river drops from the higher elevation of the Piedmont to the lower elevation of the Coastal Plain. This change in elevation causes the river to “fall."
Source: Georgia Public Broadcasting
The formation of the fall line is closely tied to the broader geological history of Georgia. The Piedmont region, which lies to the north of the fall line, consists of metamorphic and igneous rocks that were formed during the collision of tectonic plates and the formation of the Appalachian Mountains 320 to 260 million years ago, These rocks are much older and more resistant to erosion compared to the sediments of the Coastal Plain.
The Coastal Plain, which extends south of the fall line, is composed of younger sedimentary rocks and sediments that were deposited during the Late Cretaceous period (100 to 66 million years ago.) These sediments were laid down in a shallow sea that covered much of the southern part of Georgia.
The formation process of the fall line involves several factors:
- Erosion: The fall line forms where hard, erosion-resistant rocks of the Piedmont meet the softer, more easily eroded sediments of the Coastal Plain. As the river flows over these hard rocks, it erodes the softer sediments downstream, creating a steep gradient and resulting in waterfalls and rapids.
- Channel Depth: The force of the river carves a deeper channel through the softer Coastal Plain sediments compared to the harder Piedmont bedrock. This difference in channel depth gives rise to the rapids and waterfalls as the water cascades from the higher elevation of the Piedmont to sea level at the fall line.
- Geological Formations: The Oconee River fall line is associated with specific geological formations, including the Black Mingo Formation, Gaillard Formation, Snapp Formation, and Steel Creek Formation. These formations contribute to the unique geology of the region and the formation of the fall line.
- Environmental Impact: The fall line has played a crucial role in the region's history and ecology. It served as a natural barrier for boats traveling upriver, making further navigation impossible due to the waterfalls and rapids. Additionally, the energy released by the waterfalls and rapids was harnessed for hydroelectric power and industrial purposes, leading to the establishmentof cities and mills along the fall line.
In summary, the Oconee River fall line is a result of the interaction between hard Piedmont rocks and softer Coastal Plain sediments, leading to the formation of waterfalls and rapids. South of the fall line, sandy soils predominate and wide floodplains have developed along many of the streams in this region. To the north of the fall line, clay soils and narrower stream valleys are the rule. The fall line has significant historical, ecological, and industrial importance in the region.
Sources
geology.blogs.wm.edu
Georgia Public Broadcasting
New Georgia Encyclopedia
NCESC.com
US Geological Survey
Parking for the Earthcache is in the Oconee River Greenway Park and Riverwalk. The park offer trails, paths, and boardwalks to walk, jog, bicycle, and geocache along the Oconee River. The Greenway also provides fishing stations and a boat ramp. The Oconee River Greenway along the Oconee River in Milledgeville opened in 2008.