As volcanic activity often provides conditions for petrification, one might surmise Yellowstone National Park to be a good laboratory in which to study the mechanics of the process.
That would be an apt conclusion. Yellow National Park has probably the highest concentration of petrified wood anywhere, with by some estimates, 27 or more separate petrified layers spanning three thousand vertical feet.
The process is easy to visualize; an eruption buries a forest, and thousands or millions of years elapse during which the trees are petrified. As the covering gives rise to another forest layer, another eruption buries this one. And so the process continues for millions of years.
Trees have been found petrified in vertical and horizontal positions. Horizontal trees may have been covered in mudslides, or transported by flood waters to a different location. Vertical trees may simply have been covered by ejecta and fossilized where they stood.
Species of extant trees found in Yellowstone include maple, redwood, birch, hickory, pine, Sago palm, oak. elm, willow, sycamore, and other species, some now extinct. The variety of species attests to the varying climate YNP has seen over millions of years.
The caldera where Yellowstone Lake formed is that of a dormant super volcano. A super volcano is defined as a volcano ejecting 1000 or more cubic kilometers (240 cubic miles) of material. As a comparison, the 1980 eruption of Mt. St. Helens ejected 0.3 cubic kilometers of material. Yellowstone has erupted three times in the last two million years. There have been no super volcano eruptions in historic times. The effects of a super volcano eruption would be felt worldwide.