What is an EarthCache?
According to Groundspeak and the Geological Society of America, an “EarthCache is a special geological location people can visit to learn about a unique feature of the Earth. Visitors to EarthCaches can see how our planet has been shaped by geological processes, how we manage its resources, and how scientists gather evidence.” To claim a find for this EarthCache, you will have to provide answers to questions by observing a specimen of petrified wood. See http://www.earthcache.org/ for more information.
Know before you go: It is recommended to park at 125 Science Drive (near Duke Chapel) and walk to this EarthCache. It is only a short walk to the Biological Sciences building. The trails map on the Geocaching app highlights many paths around campus to walk on. **Parking may be tricky to find on certain days**
This EarthCache is located outside of the Biological Sciences building near the main entrance. The specimen of petrified wood is located here in red:
What is petrified wood?
Petrified wood is fossilized wood. Petrification occurs when tree-like organic material gets replaced by minerals. As a result, petrified wood can come in all sorts of colors. In order for petrification to occur, a tree must be buried in sediment; this is crucial as detritivores decompose dead wood when exposed to oxygen. Once the tree becomes buried, permineralization must occur for petrified wood to form. This process flushes mineral-rich water to areas in the tree. Permineralization deposits minerals and allows them to “replace” the cellulose in a tree’s cell walls.
Araucarioxylon arizonicum:
The petrified wood specimen at the GZ comes from the Araucarioxylon arizonicum tree. It is the state fossil of Arizona and is only found in northeastern Arizona (Petrified Forest National Park) and New Mexico. This region of the United States is known as the Chinle Formation. Many rocks found in this area are sedimentary in origin and were deposited by river systems (fluvially). As a result, mudstone, sandstone, and conglomerates are common rock types here.
Common minerals in petrified wood and their corresponding colors:
- Copper → green and blue
- Cobalt → deep blue
- Iron → brown and red
- Manganese → pink and orange
- Carbon and carbon-containing compounds → black
Logging Tasks:
- Take a few moments to examine the rock. What is the texture and size of the rock?
- What colors do you observe in the rock?
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Based on the colors you’ve observed, what compounds are found in this specimen of petrified rock?
- (optional) Please provide a photo of yourself, your GPSr, or a personal item that proves that you have visited this site. Please post this in your log.
Sources:
https://ucmp.berkeley.edu/paleo/fossilsarchive/permin.html
https://www.pinalgeologymuseum.org/index.php/exhibits-events/online-exhibits/araucarioxylon-arizona-s-state-fossil
https://www.rockseeker.com/petrified-wood/#:~:text=The%20Different%20Colors%20of%20Petrified%20Wood&text=The%20main%20colors%20you'll,presence%20of%20different%20mineral%20inclusions
https://geology.com/stories/13/petrified-wood/
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