How did the (petrified) trees get petrified?
A. Although the process of petrification is not completely understood, we do know that certain elements are required. First, the tree must be rapidly buried in order to minimize decay of the organic (woody) material. The petrified trees of Yellowstone were buried by volcanic deposits and mudflows associated with volcanic eruptions 45-50 million years ago. Second, there needs to be a concentration of silica in the groundwater surrounding the buried tree. In Yellowstone, silica-rich groundwater soaked into the trees, filling in the spaces between wood cells, and eventually hardening. The actual woody material is still there. Paleodendrochronologists (scientists who study ancient trees) can determine the species of tree by applying an acid solution to thin slices of the petrified material. The acid eats away the silica, leaving the woody material relatively intact. By studying this remaining cellular material, scientists can tell us, for instance, that a particular tree was a redwood. Las
