Petrified Forest National Park is a United States national park located in Navajo and Apache counties in northeastern Arizona. The park is named for its large deposits of petrified wood and covers about 346 square miles (900 square kilometers). It includes dry shrubland areas and colorful, eroded rock formations called badlands. The park’s headquarters is about 26 miles (42 km) east of Holbrook along Interstate 40 (I-40). This highway runs alongside the BNSF Railway’s Southern Transcon, the Puerco River, and historic U.S. Route 66, all of which cross the park from east to west. The park’s northern area extends into the Painted Desert. It was declared a national monument in 1906 and became a national park in 1962. In 2018, the park welcomed 644,922 visitors for recreation.
The park averages about 5,400 feet (1,600 meters) in elevation and has a dry, windy climate. Summer temperatures often reach 100 °F (38 °C), while winter temperatures can drop below freezing. Over 400 plant species grow in the park, including grasses like bunchgrass, blue grama, and sacaton. Animals found in the park include pronghorns, coyotes, bobcats, deer mice, snakes, lizards, seven types of amphibians, and more than 200 bird species, some of which live there year-round and others that migrate. About one-third of the park, or 50,260 acres (79 square miles; 203 square kilometers), is designated as wilderness.
The Petrified Forest is famous for its fossils, especially petrified wood from trees that lived during the Late Triassic Epoch, about 225 million years ago. These fossilized logs are part of the Chinle Formation, a rock layer that gives the Painted Desert its colorful appearance. About 60 million years ago, tectonic forces pushed the Colorado Plateau upward, exposing it to erosion. Wind and water have removed most of the rock layers above the Chinle Formation, except for recently formed layers in parts of the park. In addition to petrified wood, the park has fossils of Late Triassic plants like ferns, cycads, and ginkgoes, as well as animals such as phytosaurs (large reptiles), amphibians, and early dinosaurs. Scientists have studied these fossils in the park since the early 1900s.
The first human inhabitants of the area arrived about 13,000 years ago. These people, known as Clovis-era people, are ancestors of Native Americans. Around 2,500 years ago, Ancestral Pueblo farmers grew corn and lived in underground homes called pit houses within what is now the park. By about 1,000 years ago, Ancestral Pueblo farmers built above-ground homes called pueblos and gathered in large communal buildings called great kivas. By 1450 CE, many Ancestral Pueblo farmers moved to join growing communities on the Hopi Mesas to the northwest and the Pueblo of Zuni to the east. These areas are still home to thousands of descendants today. More than 1,000 archaeological sites, including petroglyphs, have been found in the park. These places remain important to descendant communities. In the 16th century, Spanish explorers visited the area. By the mid-1800s, a U.S. team had surveyed a route through the region and noted the petrified wood. Later, roads and a railway followed similar paths, leading to tourism and the removal of fossils before the park was protected. Theft of petrified wood continues to be a problem in the 21st century.
Geography
Petrified Forest National Park is located on the border between Apache County and Navajo County in northeastern Arizona. The park is about 30 miles (50 km) long from north to south. Its width changes, with the widest part being about 12 miles (20 km) in the north and the narrowest part being about 1 mile (1.6 km) in a corridor between the north and south. The park widens again to about 4 to 5 miles (6 to 8 km) near the southern end.
Interstate 40, the former U.S. Route 66, the BNSF Railway, and the Puerco River cross the park, generally running east–west along a similar path. Adamana, a ghost town, is about 1 mile (1.6 km) west of the park along the BNSF Railway tracks. Holbrook, a nearby city, is about 26 miles (40 km) west of the park’s headquarters along Interstate 40. Park Road runs north–south through the park, connecting Interstate 40 near the park’s headquarters on the north to U.S. Route 180 on the south. Historic Highway 180, an earlier version of the modern route, crosses the southern edge of the park. Like Route 66, it is no longer used and is closed. Many unpaved roads, which are not open to the public, cross Park Road at different points.
The area of the park managed by the National Park Service covers about 230 square miles (600 km²). The Navajo Nation borders the park on the north and northeast. Other lands, including state-owned land, federal land managed by the Bureau of Land Management, and private land used for cattle ranching, are located along the park’s other sides. The park’s elevation ranges from a low of 5,340 feet (1,630 m) along the Puerco River to a high of 6,230 feet (1,900 m) at Pilot Rock. The average elevation is about 5,400 feet (1,650 m). The landscape changes from gentle hills and areas with petrified wood deposits in the south to eroded badlands in the north. Most of the park’s streams, including Lithodendron Wash, Dead Wash, Ninemile Wash, and Dry Wash, flow into the Puerco River. In the southern part of the park, Cottonwood Wash and Jim Camp Wash flow into the Little Colorado River.
Geology
Petrified Forest National Park is famous for its fossils, especially of trees that lived during the Late Triassic Epoch of the Mesozoic era, about 225–207 million years ago. During this time, the area that is now the park was near the equator on the southwestern edge of the supercontinent Pangaea, and the climate was wet and warm. What is now northeastern Arizona was a low plain surrounded by mountains to the south and southeast and a sea to the west. Streams flowing from the mountains carried sediment and organic matter, including trees, plants, and animals, into the water. While most organic material decays or is eaten by other organisms, some is buried quickly and becomes fossilized. The fossil logs that give the park its name are part of the Chinle Formation.
The Chinle Formation, which is visible in many parts of the southwestern United States and gives the Painted Desert its name, is up to 800 feet (240 m) thick in the park. It contains layers of soft, fine-grained rocks like mudstone, siltstone, and claystone—much of it bentonite—as well as harder rocks like sandstone, conglomerate, and limestone. When exposed to wind and water, the Chinle erodes into badlands with cliffs, gullies, mesas, buttes, and rounded hills. The bentonite clay in the Chinle swells when wet and shrinks when dry, causing cracks and making it hard for plants to grow. Without plant cover, the Chinle erodes more easily.
About 60 million years ago, tectonic movements began to lift the Colorado Plateau, which includes the Painted Desert. Over time, parts of the plateau rose to 10,000 feet (3,000 m) above sea level. This movement caused erosion to gradually wear away the plateau. A gap in the rock record, called an unconformity, exists in the park, where erosion removed all rock layers above the Chinle except those from the last few million years. The Bidahochi Formation, deposited 4 to 8 million years ago, sits directly on top of the Chinle, while layers from the Jurassic, Cretaceous, and much of the Tertiary periods are missing.
During the time the Bidahochi Formation was deposited, a large lake covered much of northeastern Arizona. The lower layers of the Bidahochi contain silt, sand, and clay from rivers and lakes. The upper layers include ash and lava from nearby and distant volcanoes. Although much of the Bidahochi has eroded, some remains are visible in the northern part of the park, including on Pilot Rock and along the edge of the Painted Desert. Erosion has exposed volcanic landforms called maars, which are flat-bottomed, circular craters formed by volcanic explosions. A maar vent can be seen from Pintado Point.
During the Quaternary Period (2.6 million years ago to today), windblown sand and alluvium covered much of the Chinle and Bidahochi. Older dunes are 500,000 to 10,000 years old, depending on their location. Younger dunes, about 1,000 years old, are stabilized by grasses and other plants and are found throughout the park.
During the Late Triassic, trees that fell into river channels in what is now the park were buried by sediment containing volcanic ash. Groundwater dissolved silica from the ash and carried it into the logs, where it formed quartz crystals that replaced the organic material. Iron oxide and other substances mixed with the silica to create the varied colors in the petrified wood.
In Petrified Forest National Park, most logs retained their original shape during petrification but lost their internal structure. However, some logs and many petrified animal bones still have cells and spaces filled with minerals, preserving much of their original organic structure. These permineralized fossils allow scientists to study the cellular makeup of ancient organisms using a microscope. Other organic material, such as leaves, seeds, pinecones, pollen, spores, stems, and remains of fish, insects, and animals, is preserved as compression fossils, flattened by layers of sediment above until only a thin film remains in the rock.
Much of the park’s petrified wood comes from Araucarioxylon arizonicum, an extinct conifer tree. Some trees in the northern part of the park are from Woodworthia arizonica and Schilderia adamanica. At least nine species of fossil trees from the park have been identified, and all are extinct. The park also has many other fossils, including over 200 types of fossil plants from the Chinle Formation. These include lycophytes, ferns, cycads, conifers, ginkgoes, and other unclassified plant groups. The park is also home to one of the most diverse collections of Late Triassic vertebrate fossils, including early theropod dinosaurs, crocodile-line archosaurs, amphibians, and other reptiles. Fossil invertebrates include freshwater snails, clams, and the oldest known fossil crayfish, Enoploclytia porteri, which is classified in the family Erymidae.
New animal species first discovered in the park, some of which are only found there, include those listed below.
Climate
According to the Köppen climate classification system, Petrified Forest National Park has a cold semi-arid climate (BSk). The United States Department of Agriculture reports that the plant hardiness zone at the Painted Desert Visitor Center, located at an elevation of 5,764 feet (1,757 m), is 7a. This zone has an average annual extreme minimum temperature of 3.1 °F (−16.1 °C).
Winter winds in the area can reach speeds of 60 miles per hour (97 km/h). Summer breezes are lighter, but the average wind speed of 10 miles per hour (16 km/h) leads to frequent sandstorms and dust devils. Some dust devils rise to altitudes of several thousand feet.
Rainfall is heaviest from July through September, during which 42 percent of the park’s annual average precipitation falls. August is the wettest month. At elevations above 5,000 feet (1,500 m), the park may experience light snow from October through March. However, snow cover rarely lasts long. The annual average relative humidity of the area is below 50 percent and sometimes drops below 15 percent.
History
More than 1,200 archaeological sites have been found inside Petrified Forest National Park. Evidence shows that the first people lived there over 12,000 years ago. Clovis and Folsom-type spear points made from petrified wood are among the earliest artifacts found in the park. Between 8000 and 1000 BCE, during the Archaic Period, nomadic groups set up seasonal camps in the Petrified Forest. They hunted animals like rabbits, pronghorn antelope, and deer and gathered seeds from Indian ricegrass and other plants. By at least 1000 BCE and through the Basketmaker II period (400 BCE–500 CE), Ancestral Puebloan farmers began growing corn. Between 200–500 CE, the population grew quickly. Many families built homes in the Petrified Forest and stayed there all year for the first time.
During the Basketmaker III period (500–700 CE), families lived in shallow underground pit structures, first on high ground and later near bluffs and in lowlands with better soil. Settlement patterns changed, and the population grew during the Pueblo I era (700–900 CE). For the first time, large groups of families formed villages together. Each household built large, well-insulated underground homes to stay warm in winter and above-ground rooms made of stone and jacal (similar to adobe) for food storage and daily activities in warmer months. During the early Pueblo II period (900–1050 CE), Ancestral Pueblo farmers began building above-ground masonry homes, such as Agate House, a small structure made from petrified wood open to the public. This showed a greater focus on permanent homes. During the Late Pueblo II and Early Pueblo III periods (1050–1225 CE), the local population grew rapidly. Nearly 1,000 sites from this time have been found in the park, located near washes, seeps, and sand dunes.
Between 1250 and 1450 CE, Ancestral Pueblo families lived in large, apartment-like masonry buildings called pueblos, with hundreds of people living together. These villages were often near water sources. Two large pueblos were built: Stone Axe, about 0.5 miles east of the park, and Puerco Pueblo, which overlooks the Puerco River near the center of the park. At Puerco Pueblo, about 200 rooms were built around an open plaza. Some rooms had no windows or doors and were entered through holes in the roof. At its peak, about 200 people lived there. Over time, Ancestral Pueblo families moved to towns like the Hopi Mesas in northern Arizona and the Pueblo of Zuni in northern New Mexico. Some researchers believe a dry climate caused people to leave, and the last residents left Puerco Pueblo around 1380 CE.
At Puerco Pueblo and other sites, petroglyphs—images, symbols, or designs—have been carved into rock surfaces, often on a natural coating called desert varnish. Most petroglyphs in the park are estimated to be between 650 and 2,000 years old.
From the 16th to 18th centuries, explorers passed near or through the area, calling it El Desierto Pintado, the Painted Desert. However, the park’s oldest Spanish inscriptions date to the late 19th century.
After the Southwest became part of the United States, explorers searched for east–west routes along the 35th parallel. In 1853, U.S. Army Lieutenant Amiel Whipple surveyed the Petrified Forest and named a stream Lithodendron Creek (Stone Tree Creek) due to the petrified wood along its banks. Geologist Jules Marcou, part of the expedition, noted the petrified trees were from the Triassic period.
A wagon road built between 1857 and 1860 used camels for transport. In the late 19th century, settlers and stagecoach companies used similar routes. Cattle ranches were developed on the grasslands, and cattle grazed in the Petrified Forest until the mid-20th century.
The Atlantic and Pacific Railroad, opened in the 1880s, led to towns like Holbrook and Adamana. Visitors could stop at Adamana’s train station, stay in hotels, and tour the area, then called the Chalcedony Forest. The railroad later became the Atchison, Topeka and Santa Fe Railway, and then the BNSF. More than 60 BNSF trains pass through the park daily. U.S. Route 66, a former highway built in 1926, ran parallel to the railroad until 1985. A small section of the road remains in the park. Interstate 40, which crosses the park, replaced the older highway.
Increased interest in petrified wood in the late 19th century led to calls for protection. In 1895, the Arizona Territorial Legislature asked Congress to create a national park, but this failed. In 1906, the Antiquities Act, signed by President Theodore Roosevelt, established the Petrified Forest National Monument. Between 1934 and 1942, the Civilian Conservation Corps built roads, trails, and structures in the monument, and the government added land in the Painted Desert. The monument became a national park in 1962. Six years after the Wilderness Act was signed in 1964, wilderness areas were designated in the park. In 2004, President George W. Bush signed a bill to expand the park from 93,353 acres to 218,533 acres. Theft of petrified wood remains a problem. Despite seven rangers, fences, signs, and fines, about 12 short tons of fossil wood are stolen yearly. Some stolen wood is returned by visitors but cannot be returned to the park because its origin is unknown. Park rangers place it in The Conscience Pile.
Jessee Walter Fewkes, the first archaeologist to visit Puerco Ruin, predicted it would yield many artifacts in the late 19th century. Conservationist John Muir excavated the ruin in 1905–06 but did not publish his findings. He urged the federal government to protect the Petrified Forest. Professional archaeological work in the park began in the early 20th century with Walter Hough’s excavations. In the 1930s, the Civil Works Administration funded research by archaeologists
Biology
Petrified Forest National Park includes two main types of natural vegetation. The first is a Grama Bouteloua / Galleta Hilaria steppe, which is a type of grassland, and a Desert Grassland form. The second is a Juniper / Pinyon pine type, which includes a Great Basin montane forest / Southwest Forest form.
A 2005 survey found that 447 plant species live in the park, 57 of which are invasive. The park is famous for its fossils and eroded badlands, but its main environment is a semi-desert shrub steppe. Because it has been protected from development and overgrazing for many years, the park has some of the best grasslands in northeastern Arizona. In the northern part of the park, the volcanic soils of the Bidahochi Formation support many plants along the Painted Desert rim. This area is covered with shrubs, small trees, grasses, and herbs, unlike the bare badlands below.
More than 100 grass species grow in the park, many of which are native to the region. Flowering plants such as evening primrose, mariposa lily, and blue flax, and shrubs like sagebrush, saltbush, and rabbitbrush also grow among the grasses. Native perennial bunchgrasses, blue grama, sacaton, sideoats grama, bearded sprangletop, and bush muhly are common. Invasive plants such as annual lovegrass and brome (cheat grass) grow quickly and crowd out slower-growing native plants.
Trees and shrubs grow in riparian zones along the park’s washes. Willows and cottonwoods are the largest plants in these areas, along with rushes and sedges. The invasive Eurasian tamarisk, also called saltcedar, harms native plants by using most of the water, crowding them out, and increasing soil salt levels through its leaves.
Large animals that live in the grasslands include pronghorns, black-tailed jackrabbits, Gunnison’s prairie dogs, coyotes, bobcats, and foxes. Pronghorns are the fastest land animals in North America, reaching speeds of 60 miles per hour (97 km/h). They are the second-fastest land animals on Earth. Jackrabbits have large ears with blood vessels that act as heat exchangers to help them regulate body temperature. These hares use speed, long jumps, and zigzag movements to escape predators like golden eagles. Prairie dogs live in large colonies called "towns," where other animals find food and shelter. Coyotes eat mostly rodents but also consume fruits, reptiles, insects, small mammals, birds, and carrion.
Bobcats and bullsnakes hunt small animals like deer mice and white-tailed antelope squirrels in riparian areas. Western pipistrelle bats eat insects, and pallid bats eat beetles, centipedes, cicadas, praying mantises, scorpions, and other arthropods. Small animals find food and shelter among the dense plants on the Painted Desert rim, and mule deer sometimes visit the area.
More than 16 types of lizards and snakes live in the park. They eat insects, spiders, scorpions, other reptiles, and small mammals. The collared lizard, which is the largest and most commonly seen, lives in all habitats. Plateau striped whiptails, a species made up only of females, prefer grasslands and developed areas. Side-blotched lizards live in rocky areas but are rarely seen. Gopher snakes, which sometimes mimic rattlesnakes when disturbed, are common. The Prairie rattlesnake, the only venomous snake in the park, prefers grasslands and shrub areas.
Seven types of amphibians live in the park. These animals absorb water through their skin instead of drinking it. Tiger salamanders, found in grasslands and near major drainages, are the only salamander species in Arizona. Woodhouse’s toads, which are rarely seen, are the largest toads in the park. They live in grasslands, riparian corridors, and developed areas. Red-spotted toads are most active during the rainy season, July through September, and live near streams and in canyons. The Great Plains toad, the most common toad in the park, prefers grasslands. Resident spadefoot toads include New Mexico, plains, and Couch’s varieties.
A 2006 survey identified 216 bird species in the park since it became protected in 1906. Of these, 33 breed in the park, 6 likely do, and 18 live there year-round. Thirty-five species are present only in summer, and 11 only in winter. The greatest variety of birds occurs during fall and winter migrations.
Raptors, songbirds, and ground birds live in the park’s grasslands. The Puerco River’s riparian corridor is a good place for year-round residents and migrating birds like warblers, vireos, avocets, and killdeer. Developed areas near the visitor center and museum attract western tanagers, hermit warblers, house finches, and others. Occasional shorebirds and eastern birds also visit the park.
Common birds in the park include the common raven and the western meadowlark, known for its song. Anna’s hummingbird, which can hover and fly backward, is one of the smallest birds. The largest is the golden eagle, with a wingspan of up to 7 feet (2 meters).
Activities
The park is open every day except Thanksgiving and Christmas, and its hours change slightly depending on the time of year. In 2010, the park, Painted Desert Visitor Center, and Rainbow Forest Museum were open from 7 a.m. to 7 p.m. between May 9 and September 6. During other times of the year, they opened as early as 8 a.m. and closed as late as 5 p.m. The Painted Desert Inn, a historic museum and bookstore, is open from 9 a.m. to 5 p.m. all year except Christmas. Park clocks always show Mountain Standard Time because Arizona does not use Daylight Saving Time.
The Painted Desert Visitor Center, designed by architect Richard Neutra, is part of the Painted Desert Community Complex Historic District, which is listed on the National Register of Historic Places. Eight other sites in the park are also on the National Register. These include the Painted Desert Inn and its cabins, the Agate House Pueblo, the Painted Desert Petroglyphs and Ruins Archeological District, the Newspaper Rock Petroglyphs Archeological District, the Puerco Ruin and Petroglyphs, the Flattop Site, the Twin Buttes Archeological District, and the 35th Parallel Route (also called the Beale Camel Trail). The Painted Desert Inn was recognized as a National Historic Landmark in 1987.
The Painted Desert Visitor Center, located near the park’s north entrance, provides visitor information and shows a 20-minute orientation movie, "Timeless Impressions," every half-hour. It also has a bookstore, exhibits, a restaurant open from 8 a.m. to 3 p.m., a gift shop, a gas station, a post office open from 11 a.m. to 1 p.m. Monday through Friday, a postal drop box, and public restrooms. The Rainbow Forest Museum, 2 miles (3.2 km) north of the park’s south entrance, offers similar services, including the "Timeless Impressions" movie, a bookstore, fossil exhibits, an interactive Triassic Virtual Tour, limited food service, a gift shop, and public restrooms. The Painted Desert Inn, 2 miles (3.2 km) north of the Painted Desert Visitor Center, provides visitor information, a bookstore, museum exhibits, and public restrooms.
There are no campgrounds or overnight lodging inside the park. Nearby communities, such as Holbrook, offer motels and other accommodations. Overnight parking is not allowed except for backpackers with wilderness hiking permits. Visitors can explore the park by car, motorcycle, commercial tour, bicycle, or hiking. The park road, parking areas, and turnouts are large enough for recreational vehicles. Off-road vehicles, including mountain bikes, are not allowed. Bicycles must stay on paved roads, such as the 28-mile (45 km) main park road, and avoid trails and unpaved surfaces, except on Old Highway 66.
The park has seven maintained hiking trails, some paved, with lengths ranging from less than 0.5 miles (0.8 km) to nearly 3 miles (4.8 km). Pets are allowed on these trails if kept on a leash, but bicycles are not. The trails are named Painted Desert Rim, Puerco Pueblo, Blue Mesa, Crystal Forest, Giant Logs, Long Logs, and Agate House. There are also nine recently developed day-hike routes called "Off the Beaten Path" hikes, which are unpaved and largely unmarked. Hikers and backpackers can also visit the park’s wilderness areas. Free permits are required for overnight stays and are available at the Painted Desert Visitor Center, Painted Desert Inn, and Rainbow Forest Museum. Most backpackers enter the wilderness at the north end of the park, where parking and an access trail are available at the Painted Desert Inn. Group camping is limited to eight people. Horseback riding is allowed in the wilderness areas, and water for horses is available at the service station near the Painted Desert Visitor Center. Visitors are encouraged to stay on dry washes to protect fragile desert soils.
Rangers offer programs about the park. Regular events include a tour of the Painted Desert Inn, a Triassic program at the Rainbow Forest Museum sunroom, a talk or walk along the Giant Logs Trail, and a guided walk at the Puerco Pueblo. The park hosts special events during Earth Science Week and National American Indian Heritage Month. On Saturdays from Memorial Day weekend through Labor Day, artisans at the Painted Desert Inn demonstrate cultural practices related to ancient peoples, intertribal relationships, and European-descent cultures. Rangers also provide educational materials and field-trip talks for students and teachers. Some summers, artists-in-residence work in the park.