Millions of years ago, some of the largest lava flows on earth poured over this area again and again. Enormous floods of molten lava flowed out from long, parallel vents, burying the area in more than 5,000 feet of basalt.
In all, more than 300 individual lava flows inundated parts of the Columbia Basin. One of these, called the Gingko flow, buried ancient Vantage Lake under a thick layer of basalt. Water-soaked logs in the lake were slowly petrified, forever preserving them as stone.
Setting the Stage
The cake-like layers of basalt built the foundation of the region. When the Ice Age floods swept across eastern Washington and down the Columbia River, they carved long, steep-walled flood channels deep into the basalt bedrock.
More than 40,000 cubic miles of basalt lava covered parts of Washington, Oregon, and Idaho.
Several layers of basalt are visible in the cliffs along both sides of the Columbia River.