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Numerous Petrified Logs

© Copyright 2002, Jess Stryker.  CC-BY-4.0 License.
Numerous Petrified Logs.  Petrified Forest National Park, Arizona.
The petrified logs are remnants of an ancient forest that once thrived in this area.  These logs were washed into a river bed and quickly buried in silt and mud.  Volcanic eruptions nearby may have resulted in tree blow down and massive mud flows that would have buried the logs.  We saw this happen in 1980 when Mt St Helens erupted in Washington State.  (See my Mt. St Helens stock photos on this website.)  The thick layer of mud cut off oxygen needed for rapid decay of the wood.  As a result the decay was much, much slower than normal (hundreds of years slower!) As the wood decayed so slowly minerals in the soil formed quartz crystals in the voids left by the extremely slowly decaying wood.  So a wood cell would decay and the void would fill with a tiny quartz crystal.   Larger voids in the wood allowed bigger and prettier crystals to form.  So if one of the logs happened to be hollow when it was buried, the hollow area allowed for the formation of  more beautiful clear crystals in what was formerly the hollow area of the trunk. Over time the forest died off and the area became desert.  Erosion exposed the petrified logs and erosion forces are responsible for them being broken into sections.  The quartz crystal tends to break in clean lines, which is why the logs appear to have been cut with a saw.

See my other petrified log photos for more on petrified wood formation