Approximately 150 miles southwest of Atlanta, in the US state of Georgia, is a network of gorges and massive gullies lovingly called Georgia’s “Little Grand Canyon.” It is considered to be one of Georgia’s “Seven Natural Wonders”, except it isn’t at all natural. These impressive canyons were created not by the action of a river over millions of years but by rainwater runoff from farm fields in less than a century.
Photo credit: John A. Kelley/USDA Natural Resources Conservation Service
Providence Canyon began forming in the early 1800s because of poor farming practices that prevailed across the nation and especially in the south. In those early days of agriculture, land was cheap, unlimited and seemingly expendable giving way to a combination of plantations, small farms, and eventually a sharecropper system that not only degraded the land but also kept farmers in debt and uneducated. Native forest cover were cleared so the land could be farmed, and no measures were taken to avoid soil erosion leading to massive loss of topsoil. Small gullies began to form and rapidly grew deeper and more extensive, until they were three to five feet deep by the 1850s. These small channels began to further concentrate runoff increasing the rate of erosion. Today, some of the gullies at Providence Canyon are 150 feet deep.
Despite its recent formation, Providence Canyon is a treasure trove for geologists and visitors alike. Erosion has exposed the geologic record of several million years within its walls, and minerals have stained the sediments, creating a wide range of colors.
Photo credit: Alexander Lerch/Flickr
Providence Canyon lies in a region that was formed by deposition of marine sediments between 59 and 74 million years ago. The soil in the top part of the canyon wall was deposited about 60-65 million years ago, just after the age of the dinosaurs. Its fairly coarse sand is a reddish color caused by the presence of iron oxide. Underneath this formation lies what is known as the Providence Sand, which makes up most of the canyon walls. It’s one hundred and nineteen feet thick and was deposited about 70 million years ago. The upper part of this layer is very fine sand mixed with a white clay. The middle layer is coarse and more colorful, with beds of yellow (limonite) and purple (manganese) deposits. The lowest and oldest layer is a black and yellow mica-rich clay. The bottom of the canyon floor was deposited about 70-74 million years ago, and is orange in color but is poorly exposed and overgrown by vegetation.
Providence Canyon continues to erode, however, the floor of the canyon is more resistant and growth of pine trees, buses and other vegetation has helped stabilize the soil.
Source…..Kaushik in http://www.amusingplanet.com