Petrified Forest National Park

Petrified Forest National Park
IUCN category II (national park)
Location	Apache / Navajo counties, Arizona, USA
Nearest city	Holbrook
Area	218,553 acres (341.5 sq mi / 885 km²)

Petrified Forest National Park is along Interstate 40 between Holbrook and Navajo, in the United States. It features one of the world's largest and most colorful concentrations of petrified wood, mostly of the species Araucarioxylon arizonicum.

The park consists of two large areas connected by a north–south corridor. The northern area encompasses part of the multihued badlands of the Upper Triassic Chinle Formation called the Painted Desert. The southern area includes colorful terrain and several concentrations of petrified wood. Several American Indian petroglyph sites are also found in the southern area. Near the south end of the park is Agate House, a Native American building of petrified wood, reconstructed during the 1930s.

Status

Chinle Formation

The Petrified Forest area was designated a National Monument on December 8, 1906. The Painted Desert was added later. On December 9, 1962, the whole monument was made a national park. It covers 218,533 acres (341.5 sq mi; 885 km²). Hiking opportunities are varied: the longest established trail in the park extends for only two miles; the others are one mile (1.6 km) or less, but there are exciting backcountry possibilities. 50,620 acres (204.9 km²; 79.09 sq mi) of the Painted Desert is protected as the Petrified Forest National Wilderness Area, accessible to anyone who wants to explore the stark, colorful, moonscapes of the badlands. This surreal playground is easily entered by a wilderness access trail at Kachina Point/The Painted Desert Inn. After a series of switchbacks the trail fades and visitors may explore wherever they would like. No permit is needed for day hikes, but a free overnight permit must be obtained at any of the visitor's centers for overnight adventures. A 28-mile (45 km) long road runs through much of the park. Landmarks include the Agate House, built of petrified wood, and the Agate Bridge, a petrified log spanning a wash.

Petrification

Agate House, made of petrified wood

The pieces of permineralized wood are fossil Araucariaceae, a family of trees that is extinct in the Northern Hemisphere but survives in isolated stands in the Southern Hemisphere. During the Late Triassic, this desert region was located in the tropics and was seasonally wet and dry. In seasonal flooding, the trees washed from where they grew and accumulated in sandy river channels, where they were buried periodically by layers of gravely sand, rich in volcanic ash from volcanoes further to the west. The volcanic ash was the source of the silica that helped to permineralize the buried logs, replacing wood with silica, colored with oxides of iron and manganese. Several major and many smaller concentrations of petrified wood occur in the park, corresponding to several stratigraphic intervals in the Sonsela Member and aptly named Petrified Forest Member of the Chinle Formation. The major concentrations have been termed "forests" (e.g. Rainbow Forest, Crystal Forest, Black Forest, etc.) although the vast majority of the fossil tree trunks are preserved in a prone position and have been transported at least some distance from their original growth areas. However, in-place stumps of trees do occur in several areas (not easily accessible to the casual visitor), and many of the logs probably did not travel far before burial.

Petrified log in Petrified Forest NP

The Chinle Formation at Petrified Forest National Park also has produced abundant fossil leaves, vertebrates (including giant crocodile-like reptiles called phytosaurs, large salamander-like amphibians called metoposaurs, some of the earliest dinosaur fossils from North America), and invertebrates (including freshwater snails and clams).

Much of the striking banded coloration of the Chinle Formation badlands that make up the Painted Desert region is due to soil formation (pedogenesis) during the Late Triassic. These paleosols (ancient soils) preserve evidence of conditions during the Triassic including the nature of the landscape and the paleoclimate. The Chinle paleosols suggest that the climate was dramatically seasonal, with distinct very wet and very dry seasons. This climate was probably similar to the modern monsoon of the Indian Ocean region, and was characteristic of tropical areas of Late Paleozoic and Early Mesozoic Earth when all the continents had assembled to form the supercontinent Pangaea.

Geological Origins

The Petrified Forest National consists of the petrified remains of the trees of the Late Triassic period, which occurred 225 million years ago. Surrounding the petrified wood are millions of years of deposition, erosion, and uplift. This has created the Chinle Formation, which is spread across northern Arizona, Nevada, Utah, western New Mexico, and western Colorado. The Petrified Forest is situated near the southern edge of the Colorado Plateau with elevations ranging from 5300 feet to 6235 feet. It was the uplift of the Colorado Plateau, starting about 60 million years ago, and the erosion that followed and continues today, which carved the present landscape. The Painted Desert badlands are made up of bentonite, a type of altered volcanic ash. It absorbs huge amounts of water and cracks, over and over again, causing massive erosion and preventing plants from growing on the sides. Some say it resembles elephant skin. Other features created by erosion in the area are mesas and buttes.

Natural history

Petrified Forest National Park is mostly badlands, a desert-like ecosystem characterized by scrubland and rock formations, but has several pockets of riparian areas where rivers and streams run through the dry landscape. The arid ecosystem is constantly worn down by wind and, less commonly, by water. The rocks gain their colors from impurities and mixtures of elements, from dark blue coal to bright clays to red volcanic rocks. The landscape is difficult to navigate because of steep slopes, loose soils, slick clay, and deep sand. Badlands, characterized by massive erosion, generally form in areas of heavy, but infrequent, rain showers, sparse vegetation, and soft sediments.

Landscape of the Petrified Forest.

The climate of the park is very similar to that of stereotypical deserts. Summers daytime temperatures can be anywhere from 90 degrees to over 100 degrees Fahrenheit. The summer breezes are lighter than the winter winds, but the 10 mph average wind still causes frequent sandstorms and dust devils, some which reach 1000 feet high. Summer nights range from the low 50s to the high 60s, a 40 degree difference from the day. July through September is generally considered monsoon season for the park. During these summer months, scattered, but violent, thunderstorms are relatively common. The annual precipitation ranges from 8 to 12 inches, 40% of it coming from the summer storms. Fortunately, the average relative humidity of the area is very low, making the heat more tolerable. June usually holds a relative humidity at around 26%, while the average August humidity is 47%. At an elevation of over 5,000 feet, Petrified Forest National Park also has distinct winter, with a chance of snow. Average winter days are 40 to 50 degrees while nighttime temperatures range from below 0 to 20 degrees Fahrenheit. Light winter snows can start from as early as October to as late as March. It doesn’t stay on the ground for long, though, due to the temperature fluctuations. Winter winds can get up to 60 mph.

The seemingly unfriendly ecosystem is, nevertheless, home to a variety of animal and plant species. A variety of mammals, amphibians, reptiles, and birds have their homes within the national park. The soil itself is alive with lichens, mosses, algae, microfungi, and bacteria. The park is one of the best sources of cryptobiotic soil in the nation, and the fragile soil ecosystem must be protected from the shoes of tourists.

Importance of the Park

Petrified wood in general is not very unique; it can be found all over the nation and the world. However, Petrified Forest National Park contains some of the largest and best-preserved petrified wood sites in the world. More importantly, the combination of the Petrified Forest and the Painted Desert provides us with an extraordinarily diverse fossil record that cannot be found elsewhere. Fossils can be found going back over 200 million years, representing the Late Triassic period. Most of the petrified trees are around 225 million years old. Aside from fossils, the park is also known for having thousands of prehistoric petroglyphs and pictographs, which are rock carvings and cave paintings left by ancient peoples. Anthropological research has shown many of the carvings to be solar calendars.

Effects on Human History

This park features one of world's largest and most colorful concentrations of petrified wood. Despite the dry conditions of the Petrified Forest, it has been inhabited for as long as 10,000 years. The Anasazi, Mongollon, and Sinagua all lived for a period in the area. By 1540, Spanish explorers passed through the area and in 1851, a captain of the US army, Lorenso Silgreaves, was the first person to publish any information about petrified wood around the park. In 1853, Julius Marcou visited the park, the first geologist to do so. The Whipple Expedition soon after led to the discovery of petrified wood in the actual park itself.

In the 1890s, people began to dynamite the pieces of petrified wood to look for gems inside. Charlers Lummis wrote about the destruction of the park by the end of the decade. This rapidly diminishing store of petrified wood alarmed the leaders of Arizona at the time and thus the impetus for creating a park came about.

Theft

Theft of petrified wood has remained a problem despite protection and despite the fact that nearby vendors sell wood collected legally from private land. Despite a guard force of seven National Park Service rangers, fences, warning signs, and the threat of a $325 fine, an estimated 12 tons of the fossil wood is stolen from the Petrified Forest every year.

Gallery

• 
  North entrance sign
• 
  Cut and polished petrified wood
• 
  Petrified trees
• 
  Section of a petrified tree trunk, probably Araucarioxylon arizonicum.
• 
  Agate Bridge, a petrified log that spans a sandstone wash.
• 
  Petrified Forest National Park Wood Landscape

See also

• List of areas in the National Park System of the United States
• Petrified Forest
• Painted Desert Inn, a National Historic Landmark in Petrified Forest National Park.
• Petrified Forest National Park Project

External links

• National Park Service website

• Petrified Forest National Park Wilderness, photo tour at National Park Service

• American Southwest, a National Park Service Discover Our Shared Heritage Travel Itinerary