This is an Earth cache located at Glacier Pools Preserve.
The glacier pools at this preserve are a type of vernal pool. A vernal pool is a seasonal wetland. They do not have an inlet or outlet like a lake or pond. Vernal pools are filled by rainfall or melting snow. They usually dry up during the summertime.
Vernal pools can be formed in several different ways. All involve water being trapped or stuck in depression. Vernal pools can even be human made; either deliberately to replace wetland areas or through activities such as mining. The vernal pools in this persevere were formed by glaciers. The action of the glaciers created the pools by erosion and scouring the Earth’s surface. The last glacial advance in Pennsylvania was around 22,000 years ago.
Vernal pools provide a habitat for a variety of animals and vegetation. Vernal pools do not contain reproducing fish populations because they typical dry out during the summer. The lack of fish helps the animals avoid predation of their eggs. Many types of amphibians, reptiles, and invertebrates occupy these pools. A few of the more unique animals to utilize vernal pools are the spotted salamander, spotted turtle, and several types of freshwater shrimp.
Wide varieties of plant life can also be found in or around vernal pools. Some pools may not have any plants growing in their basins if they are completely encompassed by trees. The pool vegetation helps to control pool temperature and reduce evaporation.
http://www.naturalheritage.state.pa.us/VernalPool_Geology.aspx
https://www.epa.gov/wetlands/vernal-pools
https://www.vernalpool.org/vernalpools
http://www.naturalheritage.state.pa.us/VernalPools.aspx
What makes a vernal pool form in the landscape? Like any other landscape feature, geologic history is a very important factor in understanding a vernal pool’s origins.
In the northeast, glaciers and glacial retreat comprise a large portion of recent geologic history. During the Pleistocene, North America was largely covered by glacial ice sheets. Over 10,000 years ago, ice sheets retreated from the northeastern North America landscape, and left chunks of ice buried in the surface. When those chunks of ice melted, the sand, mud, or gravel above them collapsed and formed “kettle holes”. Some of these kettle holes are small, shallow, circular depressions in the landscape that in present day can hold water for a period of the year and support a vernal pool ecosystem. In glacial outwash deposits composed of well-sorted sand and gravel and numerous kettle holes, there can be high densities of vernal pools.
Emerald Pond, a vernal pool located in a gravel esker, which is a type of deposit from retreating glaciers.
Glaciers can also scour the landscape and create depressions in the bedrock, and when these small basins collect water they can function as vernal pools. Depressions in the landscape can also form from melting glaciers, local erosion, or landslides. Indentations in the surface comprised of low-permeability material can form perched pools that have little to no drainage to the groundwater. Examples of these low permeable materials in the northeast include glacial till, glacial moraine deposits, and fine-grained glacial lake deposits.
Other ways that vernal pools form can be in river floodplains, where depressions can form during high water, and then hold water even when the stream has returned to normal flow conditions. Additionally, old meanders in the stream that have been cut off can continue to hold water and support vernal pool communities. Human activities can, in some cases, provide vernal pool habitat. Man-made ponds, detention basins, or quarries can sometimes support one or more vernal pool species.
Of course, the formation of a vernal pool is ultimately dependent on hydrology, because water is the most important factor in determining if a depression is simply a landscape feature, a temporary wetland, or a permanent water body. Some pools are precipitation and surface water flow-fed only, while others have influence from groundwater. Vernal pool biota are adapted to pools with temporary hydroperiods, and so the duration that these depressions hold water is very important. The duration of inundation is determined by the source of the water, as well as the permeability of the underlying geology.
References
Colburn EA (2004) Vernal pools: Natural history and conservation. McDonald & Woodward Publishing Company, Saline
At each stage there is a question for you to answer.
Stage 1 Describe what see here.
Stage 2 using a stick pick a spot near the sign and then a nother spot about 3 feet toward the water, how far did the stick go in at each spot?
Stage 3 What purpose do swamps serve?
Stage 4 How much water is in this pool? or Estimate how big is this pool.