Hard facts on Ginkgo Petrified Forest State Park

There's treasure buried in Washington's desert. It's not gold doubloons or the lost stash of infamous 1970s skyjacker D.B. Cooper.

It's petrified wood, an heirloom from ginkgo and sequoia trees that thrived across the Mid-Columbia 15 million years ago.

Hunks of these once-tropical trees hardened into stone after volcanic activity spewed ash and molten lava across the landscape during the Miocene Period.

The easiest way to see these prehistoric relics is to head to Ginkgo Petrified Forest State Park along the Columbia River near Vantage in Central Washington, just off Interstate 90.

The park features an interpretive center that's open every day during the summer months from 10 a.m. to 5 p.m. Admission is free but donations are welcome.

One of the many features of the park is a Trees of Stone Interpretive Trail. The trail is split into two segments. There's a 1.5-mile loop through sagebrush-covered hills, or you can hike a longer 2.5-mile loop.

The trail follows an exposed section of prehistoric Lake Vantage and wanders past 22 species of petrified logs that were left where they were discovered in the 1930s.

Sections of the trail are quite steep and can test a body's endurance. Taking along a bottle of water is recommended.

The interpretive center tells the fascinating story of Central Washington's prehistoric past. Visitors might be surprised to learn that the arid desert of Central and Eastern Washington was once a wet, humid ecosystem dominated by swamps, shallow lakes and forests.

During the Miocene Period, a plethora of moisture-loving trees thrived here, sort of like a jungle. Then a volcanic fissure in Southeastern Washington brought floods of molten lava gushing across the Columbia Plateau. The flows leveled the landscape.

Thousands of downed, waterlogged trees escaped annihilation but were entombed in basalt. Their burial began a slow chemical transformation in the wood that eventually turned them to rock.

The Great Northwest Nature Factbook explains that buried wood usually decays, but when the groundwater contains enough minerals and silica (which comes from volcanic ash) and penetrates the wood, it starts the process of petrifaction.

The Ginkgo Petrified Forest State Park Interpretive Center has displays showing hundreds of species of petrified wood, all polished and in various sizes. Informational videos also are shown throughout the day.

There's a picnic area on the grounds and an observation deck with a breathtaking view of the Columbia River. Next to the center is the Gem Shop, where rock hounds can find souvenirs from polished petrified wood to mystical crystals.

If, after visiting the center, you decide to go in search of your own piece of petrified wood, Saddle Mountain, 14 miles east of the center, is the place to start.

The mountain is Bureau of Land Management property and open to the public. No permit is required to dig for petrified treasure as long as it's for personal collection and not commercial use. Collectors are limited to 25 pounds a day or 250 pounds a year.