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How Does Petrified Wood Form?

The process of petrification is not completely understood because researchers have not been able to duplicate the process in
the laboratory, where it can be observed and measured. But, certain conditions that must have existed for petrification to
occur are known. Oxygen, which causes oxidation or rotting of all types of materials, would have to have been kept away
from the dead plant material to prevent it from decaying before it was preserved. Most likely, the dead plant material was
deprived of oxygen by being buried by sediments settling in water covering the plants. Much of the fossil wood found today
is a product of ancient river and flood plain environments.

After rapid burial, the tree reacts to percolating water. Three things may happen. The log may disintegrate and not be
fossilized. The log may be reduced by compression to a coal or it may become petrified. If petrification takes place,
minerals from percolating water are deposited in fluid-filled openings in the wood. This process is called
permineralization and it preserves the tissues of the wood! In some situations minerals may also substitute for the woody
tissues of the log. This process is called replacement. Most petrified woods are permineralized . The entire process is not
fully understood but is being actively studied.

The final condition, necessary for petrification, is time. The mineral replacement process is very slow, probably taking
millions of years.