Clarks Hill Dam and Lake are located on the Savannah River, 22 miles north of Augusta, GA, and 239 miles inland from the mouth of the river. Clarks Hill was the first of three multi-purpose projects to be completed by the Army Corps of Engineers in the Savannah River Basin. The lake is located in the lower Piedmont Physiographic Region, and has a rolling topography with many small streams. In 1988, the dam was renamed in honor of J. Strom Thurmond, the longest serving Senator in U.S. history, who was from Edgefield, on the South Carolina side of the lake. In Georgia, the dam is commonly still referred to as Clarks Hill.
Clarks Hill Dam is located near the "fall line" on the Piedmont Plateau, which is basically an upland of fairly strong relief, developed through continued wearing away of disordered crystalline rocks, which have been heavily weathered and disintegrated. This section includes some hilly areas and deep valleys, but no lowlands or general highlands.
The Fall Line is the boundary between the Piedmont and the Coastal Plain. Its name arises from the occurrence of waterfalls and rapids that are the inland barriers to navigation on Georgia's major rivers. Thus the cities of Columbus, Macon, Milledgeville, and Augusta developed where boats had to be unloaded on the Chatahoochee, Ocmulgee, Oconee, and Savannah Rivers, respectively. Those waterfalls and rapids occur where the rivers drop off the hard crystalline rocks of the Piedmont onto the more readily eroded sedimentary rocks of the Coastal Plain. The Georgia Department of Transportation intends to link Columbus, Macon, Milledgeville, and Augusta with the Fall Line Freeway (Ga 540) someday. Other Fall Line cities include Tuscaloosa, AL, Columbia, SC, and Richmond, VA.
The Fall Line is a boundary of bedrock geology, but it can also be recognized from stream geomorphology. Upstream from the Fall Line, rivers and streams typically have very small floodplains, if they have any at all, and they do not have well-developed meanders (curves that nearly or do reverse the direction of flow). Within a mile or so downstream from the Fall Line, rivers and streams typically have floodplains or marshes across which they flow, and within three or four miles they meander. The most pronounced example is in the Savannah River's course at Augusta, but the same change can be seen in Brier Creek, the Ogeechee River, Buffalo Creek, the Oconee River, the Ocmulgee River, Echeconnee Creek, the Flint River, Upatoi Creek, and the Chattahoochee River from east to west across Georgia.
The soils in the area consist mainly of sandy clay and sandy silt, with an overlaying porphyritic granite composed primarily of quartz and feldspar. The soil is quite erosive, and has created serious erosion problems, especially on the South Carolina shore, from wind driven rain action.
Proceeding construction of the dam, engineers took more than 150 core samples from the terrain in the area to assess bedrock composition and suitability for construction at the site. One of these core samples is on display at the Core Sample Interpretive Area below J.Strom Thurmond Dam.
To get credit for this Earthcache, please answer the following questions. We would also like you to include a picture containing (you 
) your GPSr at the core sample, but it is not required.
1. What type of stone did the engineers find in the core samples?
2. How many sections of the core sample are on display at the dam?
3. In what year was the devastating flood that spurred building of the dam?
The recreation area adjacent to the power station at the dam is open to the public, every day until 9:30 PM. DO NOT ATTEMPT TO ENTER THE FENCED AREAS OF THE POWER STATION.
Data on this page was obtained from the Army Corps of Engineers and the University of Georgia. The questions can be answered by reading signage on site.