Columbia River Basalts

The Columbia River Basalts cover more than a third of Washington State – in some places to a depth of 16,000 feet – and extend into Oregon, Idaho, and even into northern Nevada. This large volume of basalt erupted over a relatively short period of time between 17 and 15 million years ago. Because it literally flooded the landscape, it’s called “flood basalt.” Smaller, more localized flows continued to erupt until 6 million years ago. Select the different flows to see their respective extents.