Petrified wood (from the Greek root Petro meaning "rock" or "stone"; literally "wood turned into stone") is the name given to a special type of fossilized remains of terrestrial vegetation. It is the result of a tree having turned completely into stone by the process of permineralization.
How is such a transformation possible?
Well, it can only take place under the right set of circumstances.
When an organism dies, it usually decomposes. Once in a while, though, a newly-deceased tree gets rapidly buried by mud, silt or volcanic ash. This blanketing material then shields the dead tree from oxygen. As oxygen is the main driving force behind the decaying process, the smothered plant will begin to decompose far more slowly than it normally would.
Meanwhile, mineral-laden water or mud seeps into the dead tree's pores and other openings. As the tree's internal structure gradually breaks down, its organic material (wood fibers) gets replaced by minerals (mostly silicate such as quartz) and other minerals all the while retaining the original structure of the stem tissue. Over a period of a few million years, those minerals will crystalize. Unlike other types of fossils which are typically impressions or compressions, petrified wood is a three-dimensional representation of the original organic material.
Different colours
Elements such as manganese, iron and copper in the water/mud during the petrification process give petrified wood a variety of color ranges. Pure quartz crystals are colorless, but when contaminants are added to the process the crystals take on a yellow, red, or other tint.
Below is a list of contaminating elements and related color hues:
- carbon – black
- chromium – green/blue
- cobalt – green/blue
- copper – green/blue
- iron oxides – red, brown, and yellow
- managanese – pink/orange
- manganese oxides – blackish/yellow
- silicon dioxide – clear/white/grey
Petrified wood can preserve the original structure of the stem in all its detail, down to the microscopic level. You can sometimes even see the tree rings!
Little Church Tree
Geraldine Johnson, the lady that owns the tea garden, shared some info with us about this petrified tree. It was found on a local farm owned by her family called Weathering Heights and was moved to the Little Church Tea Garden. She has spoken to visting geologists who have estimated the age of this specimen to be between 250 and 300 million years old.
Cache Tasks
To claim your find on this Earth cache please send your answer for the following tasks to us via the app or email:
1) Based on what you have learnt above and from what you see in front of you what contaminating elements would you say were in the ground water while this tree was being petrified?
2) What would you estimate the height of this specimen to be?
3) In the top of the tree is a hole. How long do you esitmate this to be?
4) Close to where you are standing is a silver plaque at the base of an item that was donated to the little church. What is the item, what year was it donated in and what was the cost?
5) Post an optional picture of yourself at the Little Church.
Failure to submit your answers within 2 weeks of logging will result in your found log being deleted.