What is Petrified Wood?
Petrified wood (from the Latin 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. Petrifaction is the result of a tree or tree-like plants having been replaced by stone via a mineralization process that often includes permineralization and replacement. The organic materials making up cell walls have been replicated with minerals (mostly a silicate, such as opal, chalcedony, or quartz). In some instances, the original structure of the stem tissue may be partially retained. Unlike other plant fossils, which are typically impressions or compressions, petrified wood is a three-dimensional representation of the original organic material.
The petrifaction process occurs underground when wood becomes buried in water-saturated sediment or volcanic ash. The presence of water reduces the availability of oxygen which inhibits aerobic decomposition by bacteria and fungi. Mineral-laden water flowing through the sediments may lead to permineralization, which occurs when minerals precipitate out of solution filling the interiors of cells and other empty spaces. During replacement, the plant's cell walls act as a template for mineralization. There needs to be a balance between the decay of cellulose and lignin and mineral templating for cellular detail to be preserved with fidelity. Most of the organic matter often decomposes, however some of the lignin may remain. Silica in the form of Opal-A can encrust and permeate wood relatively quickly in hot spring environments. However, petrified wood is most commonly associated with trees that were buried in fine-grained sediments of deltas and floodplains or volcanic lahars and ash beds. A forest where such material has petrified becomes known as a petrified forest.
Elements Involved In The Formation of Petrified Wood
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 another tint.
Following 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
- manganese – 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. Structures such as tree rings and the various tissues are often observed features.
Petrified wood is a fossil in which the organic remains have been replaced by minerals in the slow process of being replaced with stone. This petrification process generally results in a quartz chalcedony mineralization. Special rare conditions must be met in order for the fallen stem to be transformed into fossil wood or petrified wood. In general, the fallen plants get buried in an environment free of oxygen (anaerobic environment), which preserves the original plant structure and general appearance. The other conditions include regular access to mineral-rich water in contact with the tissues, replacing the organic plant structure with inorganic minerals. The end result is petrified wood, a plant, with its original basic structure in place, replaced by stone.
Logging Requirements
To obtain credit for this earthcache, you will need to visit the fossilized tree stump on the campus of West Virginia University and answer questions about it. The answers can be found by using the information on the cache page and your observations at the posted coordinates Please send me a message with the five answers before logging this earthcache.
According to the sign...
1. ... What are fossilized tree stumps such as this one commonly referred to as?
2. ... Approximately how old is this fossil?
3. ... From what era on the geological time scale is this fossil from?
Based on your observations...
4. ... Estimate the size (length, width, height) of the fossilized tree stump.
5. ... Based on the color, what element is most present in the fossilized tree stump?
OPTIONAL: Take a picture of yourself at ground zero and attach it with your log. Be sure not to reveal too much of the formation to avoid giving away the answers.