This is an Earthcache – as such, there is no physical cache. Instead you will partake in a geology lesson by making observations and answering 4 questions about the Vernal Pool at the posted coordinates. Masonville Cove is open Monday through Saturday from 9 am to 4 pm, and is closed on Sunday. Admission and parking are FREE.
What is a Vernal Pool?
Vernal pools are small depressional wetlands that are found in seasonal climates throughout the world. Some of these pools may remain partially filled with water over the course of a year or more, but all vernal pools dry up periodically. Most of these pools tend to fill up in the winter with rains, spring snowmelts, and rising ground water tables.
Since Vernal Pools go through wet and dry cycles, they do not support fish. Without fish, vernal pools support species like wood frogs, spotted salamanders, mole salamanders, and fairy shrimp that utilize these temporary waters to breed.
Typically a vernal pool will go through three phases each year:
Inundated Phase - it is inundated in the Winter.
Flowering Phase - It slowly dries in the spring.
Dry Phase - it will completely dry up in the summer/fall.
Vernal pools may be found throughout Maryland, but they are more common east of Maryland's fall line and along the flatter coastal plain of the Delmarva Peninsula. Baltimore tends to stay drier than most places in Maryland. It has a seasonal climate averages 14 days of precipitation (rain, snow, sleet, or hail that falls to the ground) per year with an annual rainfall of 42.3 inches. September is the wettest month of the year, while February is its driest month.
Formation of Vernal Pools
A key formation of the vernal pools is due to the layer beneath the pool It is either bedrock or a hard clay layer in the soil that helps keep the water in the pool. Clay soils bind closely together and become impermeable to water. When it rains the water percolates until it reaches the claypan and sits there, filling up with material and water.
Vernal pools on the east coast are often found in forested areas and near swamp lands and have a heavy deposition of biomatter as a result. 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. This allows for seepage of water in and from the water table. The soils will typically have indicators of prolonged wetness such as a lack of layering, settling, may have a decay odor, and may also contain layers of roots.
Vernal pools are formed in a variety of ways. The position of the pool on the landscape can suggest its origin. Here are 5 ways they may be formed:
Floodplains - when a stream overflows its banks entering the floodplain. Some of the overflow pockets do a good job of retaining water and become vernal pools. If this continues over the years it can lead to the creation of vernal pool habitats in the form of oxbow wetlands.
Glaciers - glaciers created many isolated depressions through freezing, thawing and erosion that fill with rainwater and snowmelt. This process is similar, in fact, to the way in which kettles are created.
Sag Ponds - sag ponds form when surface water gathers in depressions formed by easily dissolved bedrock (such as limestone) underneath an impermeable soil layer. Eventually the soil sags and water gathers in the depression.
Pingos – Pingos are formed by freezing and thawing processes on moist mountainous slopes. The upper layers of soil thaw first and slowly slide over the underlying frozen soil. The result is a landscape peppered with crescent-shaped wetlands.
Human Activities - some vernal pools are created deliberately by people who wish to create wildlife habitat or to replace a seasonal wetland that was destroyed. Other pools are inadvertently created during any kind of surface disruption (mining, roadside ditches, agricultural fields, etc.) that creates shallow depressions that hold water long enough to support seasonal pool wildlife.
REFERENCES:
1. Vernal Pool Kids Video, VernalPoolChronicles, September 2013, Youtube.com
2. Bryophytes within the Vernal Pools in the Agate Desert Area of Jackson County, Oregon , Dr. Judith Harpel, University of Washington, September 2008, fws.gov
3. Ecohydrology of Vernal Pools: , Niall McCarten, Applications to Conservation, Management, Restoration and Monitoring, Department of Land, Air, Water Resources, University of California, fws.gov
4. Vernal Pool Investigators, Table Rocks, BLM Medford District, Worksheet PDF, blm.gov
5. MD Naturalist's Notes: Vernal Pools,Jane Marlow, A Marylander's Backyard Guide, March 18, 2013, wildmaryland101.blogspot.com
LOGGING REQUIREMENTS:
To log this Earthcache: Read the geology lesson above. Answer all four questions posted below and send them via e-mail or messenger contacts on my Geocaching profile.
QUESTION 1. The impermeable layer beneath the pool is usually made up of bedrock or _______?
QUESTION 2. Observe how deep the pool is. From what you have learned, what phase do you think this pool currently going through?
QUESTION 3. Of the 5 ways vernal pools form discussed above, which is the most unlikely way this Vernal Pool formed? Why?
QUESTION 4. Examine the soil in and around the pool. Do you believe that this pool is connected to the water table?
OPTIONAL PHOTO: Posting a photo that readily indicates that you (and anyone else logging the find) are at the location.
Awesnap has earned GSA's highest level:
