History

Petrified Forest National Park has a geological history that stretches back millions of years, and human history that stretches back 13,000 years.

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History Details

Petrified Forest National Park has a geological history that encompasses hundreds of millions of years, and human history that stretches back 13,000 years. The fallen trees that give the park its name lived in the Late Triassic period of the Mesozoic era, about 218 million years ago. During this time, the park was part of the supercontinent Pangaea, and the climate was humid and subtropical. What later turned into northern Arizona was a low plain, surrounded by mountains and sea. The park's signature mesas and badlands were formed about 60 million years ago, when tectonic movements began to uplift the Colorado Plateau, of which the Painted Desert, in the northern section of the park, is a part. During the Late Triassic era, downed trees stuck in river channels were buried periodically by sediment containing volcanic ash. Dissolved silica from the ash formed quartz crystals in the logs, which gradually replaced the organic matter. Traces of iron oxide and some other substances eventually combined with the silica to create the variety of colors seen in the petrified wood. At least nine species of fossilized trees have been identified, all of which are extinct. The park preserves evidence for entire ecosystems during 20 million years of the Triassic Period. Fossil evidence includes everything from pollen and spores to the earliest dinosaurs. Human history within the park begins around 13,000 years ago, and more than 600 archaeological sites have been discovered within park boundaries. Nomadic groups arrived following the last Ice Age, first establishing seasonal camps and then growing corn in the area starting around 150 BCE. By 1 CE, there were permanent houses within the park, occupied until about 800 CE. The Pueblo Builders constructed above-ground houses from around 900 to 1275 BC, and more than 200 sites have been discovered in a wide variety of locations. The large, multi-family Puerco Pueblo housed up to 200 people at its peak: modern visitors can explore the remains of the structure. Over time, the persistently dry climate led the park's residents to move on, and permanent settlement ended around 1380 CE. Spanish explorers passed through the area from the 16th to 18th centuries, and it is rumored that they were the first to call it El Desierto Pintado, the Painted Desert. In 1853, the U.S. Army surveyed the northern part of the petrified forest, and a wagon road was built between 1857 and 1860. Settlers who stayed in the area grazed cattle in the area until the mid-20th century. Famous in modern history, U.S. Route 66, which was developed in 1926, ran through the park parallel to railway tracks until it was decommissioned in 1985. Part of the road is preserved within park boundaries.

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