Ginkgo Petrified Forest State Park

  • By Cassandra Tate
  • Posted 7/26/2005
  • Essay 7396
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Ginkgo Petrified Forest State Park contains the remains of one of the most unusual fossil forests in the world. It was set aside as a historic preserve in the 1930s, after highway construction crews working on the Vantage Road unearthed what proved to be some of the rarest forms of petrified wood ever found. Located one mile north of Vantage, near the geographic center of Washington State, the park is now a registered national natural landmark.

Trees of Stone

Highway workers began finding petrified wood in the area as early as 1927, but the significance of the site wasn’t recognized until 1931, after a chance observation made by geologist George F. Beck, a professor at what was then Central Washington College of Education in Ellensburg (now Central Washington University). Beck had been driving on the Vantage Road along the Columbia River one day when he noticed a man coming down from the hills carrying a large piece of petrified wood. Beck quickly organized an initial excavation in the area. He and his students eventually identified dozens of species of prehistoric trees at the site, including the first known samples of petrified ginkgo.

The “trees of stone” are a reminder of the fact that central Washington was once vastly different from what it is today. About 15 million years ago, during what geologists call the Miocene Period, the region was wet and humid, dominated by swamps and shallow lakes surrounded by forests. Moisture-loving trees such as swamp cypress grew on the edges of the lakes, while deciduous trees such as ginkgo, maple, walnut, oak, sycamore, and horse chestnut flourished on the hillsides. Higher elevations supported thick stands of Douglas fir, hemlock, and spruce.

Species of both broadleaf and upland conifers ended up buried in the mud of small lakes and pools. Perhaps they were transported from higher elevations by mudflows produced by volcanic eruptions; perhaps the fallen trees were carried by normal rivers and flooding. Later, a volcanic fissure in southeastern Washington sent floods of molten lava across the Columbia Plateau, leveling the landscape and destroying the standing plants and trees. However, the waterlogged, mud-covered trees were left intact. When lava from the “Ginkgo Flow” contacted the water, it formed pillow basalt that further protected the trees.

Entombed in basalt, the wood slowly began a chemical transformation. As Ann Saling explains in The Great Northwest Nature Factbook, buried wood usually decays, but when the groundwater contains enough silica (picked up from volcanic ash) and other minerals, the minerals penetrate the wood in a process known as petrifaction. Some wood remains, visible under a microscope, but most is replaced by silica. Other minerals and compounds in the groundwater also percolate through the wood, adding brilliant color patterns. Over time, the wood becomes stone.

Buried Treasure

A combination of ancient floods, erosion, and human activity helped unearth the treasures buried at Ginkgo Petrified Forest. Beginning about 15,000 years ago, a series of ice dams in northern Montana collapsed, sending huge floods over eastern and central Washington. These floods eroded portions of the basalt flows that are now within the park, exposing some of the petrified wood. The Wanapum and other local Native Americans once used the material for arrowheads and other tools. Eventually, the half-buried stone logs were left to the wind and the dust.

Highway construction crews rediscovered the site while working on the Vantage Road in 1927. Geologist Beck later became the chief lobbyist for efforts to preserve the fossil forest. In 1935, he convinced the Washington Legislature to buy a key 10-acre parcel from its owner, the Smithson Company. Crews from a federal Civilian Conservation Corps camp at Vantage began extensive excavations in 1936.

The state originally planned to turn the property over to the National Park Service for the creation of a National Monument. When the park service showed little interest, the area was designated a state park. The Conservation Corps completed the excavation and built a small museum and caretaker’s cottage. The park was opened to the public in 1938.

Few people visited the park during the years of World War II. Caretakers were employed only intermittently. The buildings fell into disrepair. Some state officials and parks department employees began to think that the park was impractical. Additionally, it was learned that the 1935 deed did not properly describe the boundaries of the park, leading to a dispute between the state and adjacent property owners in 1948. The issue eventually ended up before the state Supreme Court, which upheld a lower court ruling that the state had acquired title through “adverse possession.”

State Gem

By 1975, when the Legislature adopted petrified wood as the official “state gem,” Ginkgo Petrified Forest State Park had been expanded to its present size of 7,470 acres, including 27,000 feet of freshwater shoreline on the reservoir created by Wanapum Dam, on the Columbia River four miles downstream.

The original visitors’ center, built by the CCC in the 1930s, was replaced by a larger building in 1953. Dozens of petrified logs provide distinctive landscaping outside the building. Inside are numerous displays of polished cross-sections of petrified wood. More than 50 species of petrified trees have been found in the park, along with the remains of many prehistoric animals.

Outside the Interpretive Center is a display of Native American petroglyphs, cut from nearby basalt cliffs before they were inundated by the waters rising behind Wanapum Dam, which was completed in 1963. The petroglyphs were removed from a site that included more than 300 separate figures, carved centuries ago by the Wanapum Indians. About 60 were salvaged and cemented into place behind the center.

A primary feature of the park is the 1.5 mile Trees of Stone Interpretive Trail, part of a 2.5 mile loop through the sagebrush-covered hills about two miles northwest of the Interpretive Center. The Trail follows an exposed part of the bed of prehistoric Lake Vantage. It winds past 22 types of petrified logs, partially excavated and shown in their natural habitat.

The park also includes a recreation area and campground, open daily from April through October, and on weekends and holidays from November through March.

Of the thousands of prehistoric trees that have been discovered here, only a handful have been ginkgo, the rarest variety of petrified wood. Ginkgo became extinct in North America millions of years ago. The tree survived in Asia, however, and was reintroduced to North America as an ornamental plant in the nineteenth century. A few living ginkgo trees have been planted around the park's Interpretive Center, their vibrant green leaves a startling contrast to the drab colors of the surrounding scrublands.


Ann Saling, The Great Northwest Nature Factbook: A Guide to the Region’s Remarkable Animals, Plants, and Natural Features (Portland, Ore.: Graphic Arts Center Publishing Co., 1999), 202-203; State v. Stockdale, 34 Wn.2nd 857, 210 P.2nd 686 (1949); Cathy McDonald, “Ginkgo Petrified Forest: Tread with Wonder in Ancient Path of Lava,” The Seattle Times, July 29, 2004 (; “Ginkgo,” Washington State Parks website accessed July 2004 (; "Wanapum Dam," Grant PUD website accessed May 12, 2017 (
Note: This essay was corrected on May 12, 2017.

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