This is an Earthcache – as such, there is no physical cache. Instead after reading the lesson and examining the Witness Rock at the posted coordinates, you will then answer 4 earth science questions and message me the answers. This earthcache is located on the Sensory Explorers Trail in Sky Meadows State Park with permission. When entering the trailhead, please follow the one way direction signage along the trail. For more information about hours of operation, entrance fees (also listed at the bottom of the cache page), and park rules please visit this Sky Meadows State Park LINK.

Sky Meadows is part of the Blue Ridge Mountains, which run 550 miles from Pennsylvania to Georgia. The underlying “basement rocks” of the park are granitic rocks, and were formed during a mountain building event called the Grenville Orogeny (about 1.2 to 1.0 billion years ago), which formed an early super continent refer to as Rodinia. At the time of their emergence, the Blue Ridge were among the highest mountains in the world and reached heights comparable to the much younger Alps. But after 300 million years of weathering, these mountains have slowly broken these mountains down into smaller peaks. See image below of weathering from left to right:

Here at the Stop 4 of the Sensory Explorers Trail, you can see how time and weathering have affected the “Witness Rock,” a small exposure of Sky Meadow's “basement rocks." The sign states "This rock is more than one billion years old. Formed deep within the earth, it was covered with lave 540 million years ago, compressed, pushed to the surface, and eroded." There are clues to help you discover that this was an ancient igneous rock such as finding flat sided mineral crystals of feldspar and rough crystals of quartz.

The sign goes on to say [This rock] may seem unchangeable, but over a millennia, water, wind, and ice are reducing it to small grains of silt and sand." This is called Weathering, which describes the process of breaking down rocks and minerals into soils. Much of the soils of Sky Meadows are soils that developed from the weathering from the underlying bedrock, and it's minerals now nourish new soil and feed the community of this dale.

Physical weathering, also known as mechanical weathering, is the process of rocks breaking down or wearing away while still in place without changing their chemical composition. For example, A rock tumbles over, hits another rock, and they both break apart.

Processes like temperature changes, wind, rain, and waves are a large contributor to physical weathering. Permafrost and ice wedging from the last ice age caused much of the rocks exposed to freezing and expanding. When this happens repeatedly over hundreds of years, the joints in the rocks are eventually shattered and crack apart.

Biological weathering is a gradual process that occurs when living organisms, such as plants, animals, fungi, and microorganisms, contribute to the breakdown of rocks or stabilize surfaces.

Plants cause physical weathering as their roots grow. A seed starts to grow in a crack, it’s roots put pressure on the crack, making it wider, and eventually splitting the rock.

WAYPOINT 2

This rock was just lying around a foot or so off the edge of the trail. I was able to make a good observation without stepping off the trail, so you shouldn't have to either. Take a rough note (no need to have an exact measurement) of the estimated length, width, and depth of this crystal.

LOGGING REQUIREMENTS:

To log this Earthcache: Read the geology lesson above. Answer all four questions posted below. Answers can be sent via e-mail or messenger contacts on my Geocaching profile within a reasonable time. Group answers are fine, but do not post the answers to the questions in your logs.

QUESTION 1. There is a large crack going down the center of Witness Rock. What type of weathering do you think caused this? (For example was it ice, wind, or does it appear to have been hit with a blunt object)

QUESTION 2. Describe any biological weathering you see on the Witness Rock?

QUESTION 3. Do you see any evidence of the minerals breaking down into soil on the ground around the Witness Rock?

QUESTION 4. Locate the calcite crystal at this rock at WAYPOINT 2. My belief is that this crystal formed in a vug (open space). What is the estimated size of this quartz crystal?

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:

REFERENCES:
1. Overview Fauquier County Sky Meadows State Park, Geography, 2015, website, skymeadows.info
2. The Witness Rock, Sensory Explorers Trail Stop 4, Sky Meadows State Park, Sign

HOURS AND FEES AS OF SEPTEMBER 2024:
Sky Meadows State Park is open daily from 8 a.m. to dusk, and the entrance fee for the park is $10.