Geology And Geophysics

How Petrified Wood is Formed



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The word petrify comes from the Greek word piedra, which means rock. So when someone says they were petrified it basically means they were scared into becoming as stiff as a rock. Scary episodes are for another day but for right now we shall delve into Petrified Wood. So what exactly is petrified wood? Petrified Wood can be said to be tree or plant material that has been turned into rock through a the petrification process which involves removal of oxygen and  permineralization.

Petrification process begins with the elimination of oxygen this can be done either by burying the tree/plant material or having it submerged in water over a period of time. Plant tissues have been known to be saved this way and in some cases have remained virtually intact. It is the presence of oxygen causes breakdown/rotting of plant material through oxidation. Permineralization begins with rainwater reacting with carbon dioxide to form a weak carbonic acid as it pours. Once it percolates into the ground  it becomes groundwater. The groundwater comes in contact with minerals which it dissolves until the point of maximum saturation. The mineral content is left behind due to accumulation. It is important to understand this is a time consuming process which takes place over millions of years.

Some of the minerals found within the petrified wood are silicates commonly known as quartz. In some cases there are ferrous compounds that may give a brown color/residue, copper compounds give a green hue, while aluminum silicates and manganese compounds give white and black coloration respectively. It is this wide range of coloration that it a hot item within the jewellery industry.

Where the wood is found in large accumulations, it is often referred to as petrified wood forest.  Petrified wood forests are unlike their living counterparts because they are devoid of the leafy green content. They usually resemble a field of small boulders, which appear as if they’re charred remains of the past. 

Among the renowned forests are Black Hill Petrified Forest in South Dakota, Petrified Forest National Park in Arizona, and famous Mississippi Petrified Forest among others. However the largest Petrified Forest in the world is the Petrified Forest of Lesvos in Greece, which covers approximately 58 square miles. While it would be observed that some of the fossilized flora would’ve typically be found in equatorial climes, it is important to note tectonic plate movement led to the forests’ relocation.

Despite the fact that they may be looked as sources of jewellery leading to decimation of these priceless wood, they are also valuable to geology and paleontology. In some cases, there are plant/insect organisms that lived millions of years ago that appear as if frozen in time and this has furthered an understanding of the world as it was back then. 

Sources:
www.usgs.gov

http://www.lesvosmuseum.gr

www.fs.fed.us

http://www.ucmp.berkeley.edu/paleo/fossils/permin.html

http://www3.northern.edu/natsource/earth/Petrif1.htm

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