Flat Creek:
Flat Creek is a tributary of the Chatahoochee River that is approximately 19.70 miles (31.70 km) long.The creek flows initially in a southwesterly direction, then turns sharply south at its meeting with two unnamed branches. Flat Creek's official name by the U.S. Geological Survey is the Flat Creek-Chattahoochee River sub-watershed, and drains an area of approximately 47 square miles. Flat Creek Nature Area consists of 513-acres worth of wetland in Peachtree City that extends 3.5 miles along Flat Creek, from the Lake Peachtree spillway at Kelly Drive/McIntosh Trail downstream to Highway 74. It is administered by the Southern Conservation Trust, which kindly provided their permission for these two Earthcaches. Many thanks to Ms. Akeman, Administrative Coordinator for allowing their creation.
For this Earthcache, we're going to use a few simple definitions:
Vernal Pools:
Vernal pools are seasonal hydrological features commonly found in North America that vary depending on location and geology. They form on natural depressions on the soil (basins) and serve as a location where water will accumulate at different times during the year. They also need a hard or compacted soil that is water proof to serve as its base. They need precipitation either as rain or snow melt during a particular season or seasons of the year and finally they serve as a base for the unique biological organisms that colonize and settle in this feature. These unique wetlands are not just puddles, but very important wetlands with extreme importance to its surrounding environment.
Vernal pools hold standing water for a large period of time. They are restricted to depressions in the ground that are isolated from other water bodies, so they only receive water from or as a result of precipitation. With that said, there may be few small or shallow temporary drainage paths into or out of vernal pools into other vernal pools. The location of a vernal pool may not have anything to do with the water table, as it is a closed system most of the time. At times, water can become trapped by the underlaying bedrock, creating a low infiltration rate, and holding runoff just above the water table, creating a perched water pool. However, vernal pools can also be supported by a regional water table, particularly in the Southern U.S. States, when groundwater levels intersect the vernal pool’s bottom. These groundwater-supported vernal pools are more frequent in floodplains and on landforms with coarse-textured soils within glacial outwash plains and moraines, such as swamp land.
Soil
Soils within vernal pools typically reflect the local soil types and hydrology. Soils in perched situations overlay shallow bedrock or contain fine materials, such as clay, silt, and muck. If a vernal pool is connected to the water table they will likely have coarse soils such as sand or gravel to allow for the seepage of water in from the water table. Most vernal pools in the Western U.S. are of the former type and have a short wet time periods (usually mid December to early February); while most vernal pools in the Eastern U.S. are of the latter type and have several long wet periods over the year
The soils typically have indicators of prolonged wetness, including a lack of layering, settling, may have a decay odor, and may also contain layers of roots and surface debris. Vernal pools in Northern California are mostly found in open fields, pools do not receive an annual deposition of tree leaves as they do on the eastern portion of North America. Instead, western vernal pools are mostly free of decaying biomatter for a large part of the year. On the East Coast, vernal pools are often found in forested areas and near swamp lands and have a heavy deposition of biomatter as a result.
Types of vernal pools:
Some of this information may come as a surprise to you if your exposure to these wetlands is based only on the types found on the East Coast, but there are various different types of vernal pools. These are:
- Floodplain vernal pools. These are found usually near streams or rivers. These can also be created by the natural meandering of a stream or river over time, creating an oxbow lake, or form over depressions created by rivers or streams millions of years ago.
- Sag pond vernal pools. These are bodies of water collected in the lowest parts of a depression formed between two sides of an active strike-slip zone. Sag ponds may be useful identification features in aerial photographs for mapping faults. Surface water gathers in the depression but the impermeable layer in the soil restricts surface water infiltration and creates a perched water table. Sag ponds of various sizes can be found along the San Andreas Fault and in the Sacramento Valley of Northern California.
- Glacial vernal pools. As glaciers moved and shifted, they created many isolated depressions, through the actions of ice melt, scour, and erosion that fill with precipitation and snowmelt.
- Pingo or permafrost vernal pools. Pingos can only form in a permafrost environment. Evidence of collapsed pingos in an area suggests that there was once permafrost. Pingos are formed by freezing and thawing processes on moist slopes. The upper layers of soil thaw first and slowly slide over underlying frozen soils. The resulting landscape appears to be scarred with crescent shaped wetlands.
- Artificial vernal pools. These are created by humans for various purposes, mostly related to conservation efforts in highly impacted areas.
How to log this Earthcache:
Any "Found It" logs without the complete requirements being sent in via email or message, will be deleted. Please answer to the best of your ability. I'm very lenient with answers as long as I can tell you actually visited the site. The GZ is in a suburban neighborhood and in a path frequently used by golf carts, so please be careful, mindful and respectful to the neighbors. Whenever possible, try to send the answers first.
1. Include the GC code of this Earthcache along with the names of all visitors. One set of answers is ok for a group, but include everyone in your group with the answers.
2.Depending on the time of the year, you may be able to observe the vernal pools in the area while they are flooded. In your estimation, what kind of soil forms the hardpan for the vernal pools that you can observe just a few feet north of where you stand? a) clay or; b) hard bedrock layers. Look at the soil around you for a clue.
3. What type of vernal pool do you believe this to be?
If the pool(s) around you have water, answer the following:
a.Does it smell like decaying biomatter where you stand? Why do you think this is?
b. How many vernal pools can you observe near you?
c. Describe the field you see surrounding the vernal pool(s) and tell me why you believe a vernal pool has formed in this landscape.
If the pool(s) around you are dry, answer the following:
a. From the vantage point of the observation platform, describe the soil at the bottom of the vernal pool(s) What type of soil do you think this is (clay=red; silt=brown; dry muck=green/gray)?
b. How many dry pools would you say there are when they have water?
c. Describe the vegetation around the vernal pool(s). What effect do you think the vernal pool(s) have in the quality of the soil?
4. Post a picture of yourself at the GZ. Your face doesn't need to be in the picture. You can alternatively take a picture of something that identifies you or your group (i.e. a piece of paper listing all your geo nicknames with the GZ in the background). Per the latest Earthcache guideline revision, this is no longer optional, it is now required to be able to claim your find.
Information courtesy of The Encyclopedia Brittanica; Wikipedia, and personal knowledge of geological sciences.