National Parks

Petrified Forest, oil on canvas, part of the Geology Library's artwork collection / Thomas Moran

Petrified Forest National Park is in...northeastern Arizona[, and] named for its large deposits of petrified wood...[T]he northern part [of the park] extends into the Painted Desert...[The] park is known for its fossil...trees that lived in the Late Triassic Epoch of the Mesozoic era, about 225 million years ago. Special rare conditions must be met in order for...fallen [trees] to be transformed into...petrified wood. In general, the fallen [trees] get buried in an environment free of oxygen (anaerobic environment), which preserves the original plant structure and general appearance. The other conditions [needed are] mineral rich water in contact with the [trees], replacing the organic plant structure with inorganic minerals [such as quartz].  The quartz within the petrified wood is hard and brittle, fracturing easily when subjected to stress. During the gradual uplifting of the Colorado Plateau, starting about 60 million years ago, the still buried petrified trees were under so much stress they broke like glass rods.

More than 600 archeological sites have been found inside the boundaries of Petrified Forest National Park. Evidence suggests that the earliest inhabitants of the park arrived at least 8,000 years ago,...[and Native Americans continued to inhabit the land until] about 1380 C.E. [when] Puerco Pueblo was abandoned because of a persistently dry climate.  [Today] the majority of the Navajo Nation, the largest Native American reservation in the US,...[is] located in northeastern Arizona.

[Beginning in the] 16th...century, explorers...passed near or through the area looking for routes between Spanish colonies...After the Southwest became part of the U.S., explorers continued to look for good east–west routes along the 35th parallel. The [eventual] opening of the Atlantic and Pacific Railroad in the early 1880s led to the founding of towns [which brought visitors to the area then] called the Chalcedony Forest.  Increasing tourist and commercial interest in petrified wood during the late 19th century began to alarm residents of the region...In 1906 the Antiquities Act signed by President Theodore Roosevelt was used to create the Petrified Forest National Monument. Between 1934 and 1942...the government acquired additional land in the Painted Desert section.  The Petrified Forest became a national park [on December 9th,]1962 during the presidency of John F. Kennedy.