In order to claim this Earthcache, Read the information below and submit your answers to the questions under the How to Log this Earthcache section. There is no physical container. Observe the best you can. The objective is to learn and have fun
Vernal pools are seasona hydrological features commonly found in Northern California that are formed when several factors are present. First, you need a natural basin to serve as the spot where water will accumulate. Second, you need a hard or compacted soil that is impermeable at its base. Third, you need precipitation during a particular season of the year and lastly you need the unique biological organisms that colonize and settle in this feature. These unique wetlands are not just puddles, but very important wetlands
Vernal pools hold standing water, which means they are restricted to depressions in the ground, that are isolated from other water bodies. With that said, there may be few small or shallow temporary drainage paths into or out of vernal pools, as is the case at this location. The location of a Vernal pool may not have anything to do with the water table. At times, water can become trapped by the underlaying bedrock, creating a low infiltration rate, and holding runoff above the water table, creating a perched water pool. However, vernal pools can also be supported by a regional water table, when groundwater levels intersect the pools bottom. These groundwater-supported vernal pools are more frequent in floodplains and on landforms with coarse-textured soils within glacial outwash plains and moraines.
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.
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. Since vernal pools in Northern California are moslty 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.
Types of vernal pools:
This may be a surprise to you if your exposure to these wetlands is based only on the types found on the West 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 in 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.
How to Log This Earthcache
Send me your answers BEFORE logging the find. You can log your find afterwards. I may or may not be able to respond immediately but if there is something wrong with your answers I will contact you to get a clarification.
You must visit the area in order to get credit for this Earthcache. Do NOT tresspass. You can get your answers standing on the sidewalk. Armchair finds will be deleted without explanation (see Earthcache Guidelines). In order to claim the find, send me an email using the link just below the Earthcache title with the answers to the following questions
1) 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. The keepers of this field usually have cattle grazing around on these fields. How do you think the presence of cattle affects the soil?
2) Does it smell like decaying biomatter where you stand? Why do you think this is?
3) How many vernal pools can you observe near you?
4) Describe the fields you see surrounding the vernal pool and tell me why you believe a vernal pool has formed in this landscape.
5) What type of vernal pool do you believe this to be?
6) **Updated 6/21/2019**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.
Send me the answers to these questions along with the GC code and the number of people in your party (with their geo nicknames).
Sources: Dictionary.com; Wikipedia; Encyclopaedia Britannica; personal knowledge of Earth sciences.