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 (Ginkgo Biloba)
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.
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.
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.