Vernal pools derive the rename from “Venus” relating to spring when the pool is full of water and alive with animal life.  They are also referred to as seasonal or ephermal ponds as well.   Frogs, salamanders, and toads find these to be perfect breeding grounds.   Many of these pools will dry out during the summer autumn and or freeze solid in the winter in this part of the country.  This is actually a key feature for a vernal pool versus a pond or lake.  Since they do dry out or freeze the pool cannot support potential predictors for the eggs and  tadpoles that will get their start here.    The vernal pond is important to animal life in Ohio due to the loss of wetlands over the past couple of hundred years.  Back then Ohio had 5,000,000 acres of wetland, but only 10% remain today.   The Ohio vernal pool indicator species is the spotted salamander.  So keep your eye out for this official critter!

Many geographic features can form these pools.   A depression in a woodland area, a flooded meadow near a stream or river, a coastal plain, or even some man-made features like a quarry.

A typical vernal poll is less than 3 feet deep and do not have a permanent connection to a body of water – for example they tend not to have a creek flowing into them.

Vernal Pool Formation

Below see a diagram of a typical vernal pool cross section.   The water collects here because beneath this vernal pond lies a hardpan layer.  This hardpan can be comprised of clay or bedrock.  The general characteristic of hardpan is that of being a distinct soil layer that is largely impervious to water. Claypan is a dense, compact, slowly permeable layer in the subsoil having a much higher clay content than the overlying soil. Claypan is usually hard when dry, and plastic and sticky when wet. It limits or slows the downward movement of water through the soil. This is what helps keep the water in the pond.

The Hardpan

At this site it would be difficult to be sure what the hard pan is comprised of without excavating.  But I’ll give some data below to help figure it out.

From the Ohio Dept. of Natural Resources website here is a chart of different types of soil in the state.

And a legend gives the makeup of the soil in these regions (in general)

To log this earthcache answer the following:

1)      Of the types listed above, which geographic feature formed this pool?

2)      What is the approximate diameter of the pool when you visited?

3)      Estimate the number of gallons of water in the pool.  Assume the pool is a cone with a 10 degree angle.  So the depth (“h” below) is the observed radius of the pool times   tangent  of 10 degrees  or H=(radius)( 0.17632)  and water is 7.48 gallons per cubic foot.

4)      Based on the ODNR charts above: what is most likely forming the hardpan under this pool?