The wood is then mineralized to transform it to stone. Wood is preserved from decomposition by rapid entombment in mud, particularly mud formed from volcanic ash. In addition to microbial decomposition, wood buried in an alkaline environment is rapidly broken down by inorganic reactions with the alkali. As a result, fossil wood older than Eocene (about 56 million years old or older) has lost almost all its holocellulose, and only lignin remains. The rate of decay is affected by temperature and moisture content, but exclusion of oxygen is the most important factor preserving wood tissue: Organisms that decompose lignin must have oxygen for their life processes. The lignin is hydrophobic (water-repelling) and much slower to decay. ĭead wood is normally rapidly decomposed by microorganisms, beginning with the holocellulose. The hemicellulose and lignin encrust and reinforce the cellulose microfibrils. Hemicellulose, a branched polymer of various simple sugars, makes up the majority of the remaining composition of hardwood while lignin, which is a polymer of phenylpropanes, is more abundant in softwood. Cellulose is composed of long chains of polymerized glucose arranged into microfibrils that reinforce the cell walls in the wood. Almost half of this is cellulose, which gives wood much of its strength. Together, these substances make up 95% of the dry composition of wood. Wood is composed mostly of holocellulose ( cellulose and hemicellulose) and lignin. The lack of oxygen slows decay of the wood, allowing minerals to replace cell walls and to fill void spaces in the wood. Petrified wood forms when woody stems of plants are buried in wet sediments saturated with dissolved minerals. The blue-green stains are from oxidation of the chalcocite to azurite and malachite. The black wood at left shows unusual mineralization with chalcocite and other sulfide minerals. The brown wood at right shows conventional silica mineralization. Petrified wood from the Shinarump Formation at the Nacimiento Mine, Cuba, New Mexico. A forest where such material has petrified becomes known as a petrified forest. 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. Silica in the form of opal-A, can encrust and permeate wood relatively quickly in hot spring environments. Most of the organic matter often decomposes, however some of the lignin may remain. There needs to be a balance between the decay of cellulose and lignin and mineral templating for cellular detail to be preserved with fidelity. During replacement, the plant's cell walls act as a template for mineralization. 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. The presence of water reduces the availability of oxygen which inhibits aerobic decomposition by bacteria and fungi. The petrifaction process occurs underground, when wood becomes buried in water or volcanic ash. Unlike other plant fossils, which are typically impressions or compressions, petrified wood is a three-dimensional representation of the original organic material. In some instances, the original structure of the stem tissue may be partially retained. The organic materials making up cell walls have been replicated with minerals (mostly silica in the form of opal, chalcedony, or quartz). 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. Petrified wood, also known as petrified tree (from Ancient Greek πέτρα meaning 'rock' or 'stone' literally 'wood turned into stone'), is the name given to a special type of fossilized wood, the fossilized remains of terrestrial vegetation. People are scared stiff, they're petrified of rocking the boat and losing their position.Petrified log at the Petrified Forest National Park I was more than nervous, I was absolutely petrified, and I do n’t know that that feeling ever went away. , they’re petrified that if I come into power, I will hold them accountable, they also know that even if I go to jail, we will swing the elections no matter what they do. We we’re quite surprised to see that it was not their imagination. We’ve gotten a lot of petrified wood Civil War relics from the area and that’s what I thought it was, this is our first set of teeth we’ve found. Finally, the station manager stuck his head into the studio and said, ‘Remember, this is a communicating business.’ I let the music go down and told the audience what had just happened. But every time the music faded I’d turn it back up again. I was petrified, the theme music was supposed to fade, and I was supposed to do a voice-over.
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