Picture a lush forest with trees up to 10 feet in diameter towering 100-200 feet into the air. All around is thick green vegetation growing tall in the equatorial climate. There are insects and amphibians with some mammal like creatures in the forest but no dinosaurs, birds or humans because they along with most of the animals that we know today have not yet evolved. This is the scene where the trees of the petrified forest were living. This was the Triassic period 200-250 million years ago. At this time the planet looked nothing like we know it, all the continents were joined together in one huge land mass known as Pangea, this would eventually break apart to form the continents we know today. As the continents drifted apart there were huge climatic changes. The trees died, some drifted on flood waters into a flood plain where they became covered by sediment and ash from volcano's. Chemical reactions took place in this mix causing the cell structure of the trees to crystallize and turn to quartz. Iron rich minerals combined with the quartz creating a rich rainbow of colors. The fossilized trees remained covered for millions of years while the area went through many changes. Eventually wind and rain erosion uncovered the now hard as rock trees exposing them to the desert air of what is now Arizona.