In Georgia, sand dunes or sandhills can be found in three distinct places: at the seashore, along the fall line, and along the eastern banks of Coastal Plain rivers and streams. The dunes along riverbanks and streams are also known as riverine sandhills. These dunes, found only on the eastern side of rivers, are believed to have been created by strong winds during the late Pleistocene era 20,000 years ago and formed of deep, coarse, riverine alluvial sand. Most inland eolian (wind-formed) dunes associated with rivers on the Georgia Coastal Plain probably date to glacial periods. Direct dating of the dune sand shows that dunes formed between 30,000 and 15,000 years ago.
The sandhills along the seashore mark current coastlines, while those found along the fall line show where ancient coastlines were. Unlike coastal areas and the fall line, riverine sandhills were created over time as strong westerly winds deposited exposed river bottom sand along the eastern shore of certain rivers. The dunes in the Albany area were formed by erosion of sand from the Flint River and extend over 5 miles along the eastern bank of the Flint. Today the dunes are used mostly as a recreation area for ATV riders.
Dunes found in the Georgia Coastal Plain contain important geological and paleo-environmental information, such as dune geomorphology, stratigraphy, sedimentology and types of soils. Georgia's inland dunes range from transverse to parabolic to irregular in form, typically merging to form long chains that parallel the source river or stream. Typically, the dunes are composed of 95% quartz sand grains.
Types of dunes:
• The crescentic dune, also called the barchand dune, is the most common type of sand dune. As its name suggests, this dune is shaped like a crescent moon with points at each end, and it is usually wider than it is long. Crescentic dunes form when winds blow from one direction.
• The linear dune is straighter than the crescentic dune with ridges as its prominent feature. Unlike crescentic dunes, linear dunes are longer than they are wide -- in fact, some are more than 100 miles (about 160 kilometers) long. The ridges are long and snakelike, and these dunes usually occur in parallel sets separated by other sand, gravel or rocky corridors.
• The star dune has arms that radiate out from a center pyramid-shaped mound, hence the descriptive name. Star dunes grow upward instead of outward and are a result of multidirectional winds. Common to the Sahara Desert, they tend to show up around topographic barriers. They're among the tallest sand dunes on Earth -- some star dunes in China are more than 1,600 feet (500 meters) tall.
• The dome dune is oval- or circular-shaped and has no slip face. Dome dunes sometimes appear at the ends of crescentic dunes. Most dome dunes are low -- only a few feet high.
• The parabolic dune is U-shaped, but differs from the crescentic dune because its crests point upward, with elongated arms that follow behind. A parabolic dune's trailing arms are typically anchored by vegetation. The longest known parabolic dune has a trailing arm nearly 7.5 miles (12 kilometers) long.
The coordinates will take you to a spot where you can get a good view of the dunes.
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1. From the information you read above and from what you observed during your visit to this site, what type of dunes do you think these are and why?
2. Approximately how high is the highest dune you see from the posted coordinates?
3. According to your GPS, what is the elevation at the posted coordinates?
4. Directly across the street from the posted coordinates is a single large object. What is it?
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