Background and What to Do
Petrified wood is wood that has been turned to rock. The prefix comes from the Greek word petro, meaning "stone". So, naturally by extension petrology is the study of the origin, composition and structure of rock.
Petrified wood is a special type of fossil. It is the end result of when the organic components of wood are replaced by minerals by the process of mineralisation. Generally the wood is buried under ground and due to a lack of oxygen it does not decompose. Mineral heavy water flowing through ground water infiltrates the plant cells and minerals are deposited over time as plant lignin and cellulose decay. Due to this process petrified wood retains much of the 3D structure of the original wood (unlike imprint type fossils) and it can be possible in some specimens to see the original tree growth rings. This can yield data about the climate during the time the tree was growing.
Visual inspection of a sample can yield information about the type of elements present in the water during petrification. Pure quartz is a key component but is colourless, it take on other colours when the following contributing substances are present:
- iron oxides - red, brown, and yellow
- manganese oxides - blackish/yellow
To complete this EarthCache you will apply some petrology to the petrified wood at EGZ.
Logging Requirements
0. Preface any email with GC3TA82 Scared Stiff in the subject line and title and clearly note the question number and answer. Do not wait for a confirmation email to log but be prepared to be asked for additional information if your answers are slim.
1. EITHER: accurately describe a feature of the petrified wood at GZ that proves it to be wood in origin OR email a photo of such a feature.
2. Using information found at GZ give the origin and date of formation of the petrified wood.
3. Inspect the rocks and using the list of "contributing substances" in the description state which you think have been incorporated into the rock.
Email answers to gcstegan"at"gmail.com
Stegan's EarthCache Masters Programme
It is not very feasible for many New Zealanders to get past the Bronze level on the earthcache.org programme becase you need three states for Silver which means leaving the country! So, as in 2010 I've decided to run a little sideshow on my new earthcaches this year... with the following points system:
5 points: First to find
3 points: 2nd to find
1 point: Logging a find
1-5 points: Special bonus questions.
At the end of the year, I'll issue certificates for 1st, 2nd and 3rd.
Updated information and Leaderboard at: Stegan's Earthcache Programme
