Petrified wood is created over the years when minerals mixed with water slowly take the place of the tree. An example could be after a volcanic activity. During this volcanic activity, trees fall over and are covered by a thick layer of ash. In this volcanic ash there is quartz, quartz can dissolve is hot, thermal, water. This thermal water also rises from the volcanic eruption. The quartz dissolves, finds a place in the wood and makes an impression of the tree. This is of course very succinct, in our article the origin of petrified wood you can read more about it!