Reston Rocks EarthCache
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Approximately 200 years ago, you could see gold in these hills. However, those flakes and nuggets were picked up soon thereafter. The best you can do now is check out the mostly underlying geological structures that held that treasure. In the Reston area, that can be challenging. Fortunately, the outcropping here gives you the opportunity to directly observe the structures that form the basis for Reston and much of the region.
Note: There is NO reason to leave the path to make your observations.
Park in the public parking lot of the Lake Audubon Pool (see the waypoint for the coordinates). Then walk across the boat ramp (be careful!) to the trailhead. From there, you will have a side view of the outcropping. Take a brief stroll down the trail to ground zero and check out the primary face of the outcropping.
While you do not have to leave the trail to make your observations, be alert to the possible presence of walkers and cyclists while you are there.
The outcropping at this location has a 550 million year history that made it available for your viewing. You are standing between the Glade and Hunter Folds that were formed from the interactions of super-continents.
The outcropping is formed from three primary components:
- Schist – a metamorphic rock with a medium to large mica-based grain structure that often forms into sheets.
- Phyllite – another type of metamorphic rock with finer grain coming from clay flakes. These flakes often create a luster to the rock.
- Quartz – a mineral formed from silicon and oxygen (SiO2) that was often the carrier for the gold that was extracted in colonial times.
Obscuring your view of the rocks and minerals are noticeable growths of moss, plants and trees. These flora are inexorably breaking down the outcropping. Fortunately, their effects occur quite slowly from the perspective of human lifetimes.
To claim credit for this Earthcache, please submit the following information to the cache owner via the Geocaching site messaging or e-mail:
- The primary face of the outcropping has three key regions. Using information from the cache listing, describe the characteristics of the foundation, the middle band and the top third of the outcropping. How do the regions interface?
- Estimate the width of the primary face of the outcropping at its base near the trail and the height of the primary face.
- Near the top of the outcropping is a five-inch diameter tree. Describe the effects of the tree’s growth on the rock. Over how many years would you estimate that those effects have occurred?
Please do not post photos that could include spoilers. There are many lovely views of the lake and the trail that you could share.
Congratulations to NutmegBrownie for her FTF!
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