Friday, September 19, 2014

Ginkgo Petrified Forest State Park

Basalt rocks from ancient lava flows

Erigeron (fleabane)

Artemisia tridentata (big sagebrush)

Plants of the Sagebrush Steppe

Petrified elm.  All photos were taken in October 2012

Click here for more photos of Ginkgo Petrified Forest State Park.

Ginkgo Petrified Forest State Park covers 7,470 acres in central Washington near the Columbia River north of Vantage.  The trail here is a 3-mile loop through an ecosystem known as Sagebrush Steppe, a highly xeric community of plants including big sagebrush (Artemisia tridentata) bitter-brush (Purshia tridentata) parsnip-flowered buckwheat (Eriogonum heracleoides) gray ball sage (Salvia dorrii) & bluebunch wheatgrass (Agropyron spicatum).  In October, the landscape was especially dry, although I was surprised to find some of the sagebrush in bloom.

15 million years ago, this area was filled with swamps & shallow lakes surrounded by forests. Swamp cypress grew on the edges of the lakes. Ginkgo, maple, walnut, oak, sycamore, and horse chestnut grew on the hillsidesDouglas fir, hemlock, & spruce grew nearby at higher elevations. Logs became buried in mud. 10 to 15 million years ago, lava floods spread over the area from fissures in the earth, covering the logs & allowing them to petrify. 15,000 years ago, during the last ice age, an ice sheet blocked the Clark Fork River & created Glacial Lake Missoula.  Periodically, the ice dam would fail, resulting in large floods that rushed down the Columbia River drainage, through the Columbia River Gorge & out to the Pacific Ocean. These floods exposed the petrified logs. Highway workers began finding petrified wood in 1927 while working on the Vantage Road. Crews from a federal Civilian Conservation Corps camp at Vantage began extensive excavations in 1936. The park was opened to the public in 1938.

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