The word “petrified” means “turned to stone”. Therefore, petrified wood is wood which has been turned to stone. But how does this happen? First, the tree has to die and fall down. In order for the rock to become fossilized, the fallen tree also has to be quickly buried in sediment. Over time, more and more sediment collects over top of the log. Years will pass as the tree gets buried deeper and deeper in the ground. As water from rain and streams pass over the buried tree, a small amount will travel through the sediment. The water will dissolve parts of the tree, and bring chemicals with it to also build back parts of the tree over many years.
Petrified Wood, University of Waterloo Earth Sciences Museum Collection