Chapel Hill Grit EarthCache

This is an Earthcache – as such, there is no physical cache. Instead you will partake in a geology lesson by making observations and sending me the answers to 5 questions about the Chapel Hill Grit pathways at the posted coordinates. This earthcache was placed with permission from the Director of Horticulture. Coker Arboretum is open dawn to dusk, 365 days a year and leashed pets are welcome. Metered parking is available nearby and around downtown Chapel Hill.

Before we begin the lesson, let's lighten the mood a bit with a "dad joke." QUESTION: What do you call a handful of gravel?

Give Up? The ANSWER is a "palm-o-granite!" Ha hah! Get it? It's a pun on Pomegranate. Ahh, never mind. As to why I am making this silly "gravel" joke in my Earthcache listing, prepare yourself to learn about a locally quarried resource that used to be the "walk of the town" here in this part of Orange County.

Here in Chapel Hill many of the oldest walkways and parking lots in town were made of Chapel Hill Grit. This orangish tan gravel influenced many of the architectural color themes on UNC'S North Campus, especially among the original buildings. Today, though most of the gravel paths have been replaced with brick walkways, you can still find some of the gravel sidewalks in the area, just like these side paths here at the Coker Arboretum.

Chapel Hill Grit, also known as Chapel Hill Gravel, is native to the area and used for walkways, driveways, foundations, and fill material. It packed down so densely, that once all of Chapel Hills streets were paved with it. It was even used on basketball courts, as the tightly packed grit allowed for uninhibited dribbling of the ball. Some references refer to its color as being orange, others tan, some yellow, and a few sources say that it is of a reddish white tone. Regardless of what you think the color is, most people agree it looks like sand. Geologically speaking Chapel Hill Granite is much coarser than sand, as it is larger in size.

It is also not a true "gravel" by definition, as it is made up of mostly sand-sized pieces of weathered granite (The most common types of rock found in gravel are basalt, limestone, and sandstone).

The town of Chapel Hill is located over a granite intrusion, which pushed through the surrounding volcanic slate 300 million years ago. It formed 6 miles below the surface, and after it cooled and solidified, it was uplifted with the rest of the Southeast when the Appalachian Mountains rose up 250 million years ago. Over a long period of time that granite weathered and broke down, and it was from it's decayed feldspar remains that this sand-to-gravel sized chunky Chapel Hill Grit formed.

Feldspar is the name given to a group of minerals distinguished by the presence of alumina and silica in their chemistry. It is the single most abundant mineral group on Earth, and accounts for an estimated 60% of exposed rocks, soils, clays, and other unconsolidated sediments. Potassium feldspars contain potassium, and color is commonly pink to red, but can also be white, gray, and yellowish. Plagioclase feldspars contain varying amounts of calcium and sodium, and their color is commonly white or gray. The red and yellow colors in feldspars are usually attributed to iron.

Using this local building material was a substitute for not having commercial deposits of sand or true gravel in the Orange County area. In 1969 there were five or six Chapel Hill Gravel quarries operating in Orange County. Groundskeepers at the time recalled this gravel being a "salvation" to the campus, as it was too expensive to ship in other materials in the early 20th century. Even back in 1969, crushed stone sold for $3.50 to $4 a ton, while local Chapel Hill Grit only cost only $1 a ton.

These gravel walkways may have been more convenient and less expensive when first installed, but these paths require a maintenance refresh every year or two. Chapel Hill Gravel is less permeable than traditional gravels, so water tends to stand in indentions and potholes can form. Even though this gravel packs down firmly and is resistant to washing away, after a long period of heavy rainfall, it would often wash away into local ditches. So there was a constant process of adding more gravel, compacting it, and scraping it flat so the paths didn't turn into mud puddles. Another downside of Chapel Hill grit has to do with it being perfect medium for germinating weed seeds.

It was until after World War II, Chapel Hill Granite started vanishing from the walkways on campus and around town for the more maintenance friendly brick paths. Some nostalgic Alumni complained about "desecrating tradition" when the first brick paths appeared on campus replacing those old noble gravel paths. Yet, as more and more of the campus brick was installed, those opposing voices quieted down. It became evident that most everyone preferred brick, as those old dusty gravel walkways on campus were hard on the shoes of students. The sharp quartz edges wore out leather soles quickly, and students would have to replace them multiple times a year. Also, bits of gravel would mysteriously infiltrate students shoes, causing the wearers discomfort.

Just think of all time students save because they don't have to stop to shake out their shoes and pluck off those pesky invading pebbles off of their socks.

LOGGING REQUIREMENTS:

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

QUESTION 1. While walking on the paths does it shift under your feet like your walking on sand, traditional gravel, or something more solid like cement?

QUESTION 2. Did you see any evidence of standing water, potholes, or any "wash out" on the paths during your visit?

QUESTION 3. Take a close look at the gravel path. Chapel Hill Grit has been described as many different colors. How would you describe the color of this gravel?

QUESTION 4. Which one of these two Feldspar Minerals do you think is more represented in the gravel path?
A. Potassium feldspars
B. Plagioclase feldspars

QUESTION 5. Do you agree with the campus decision to replace the grit paths with brick walkways? Why is that?

OPTIONAL PHOTO: Posting a photo that readily indicates that you (and anyone else logging the find) are at the location.

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