Geologic History and Overview

The Columbia River Gorge stretches 85 miles from the eastern edge of the Columbia and Deschutes rivers to the Western edge of Portland.  The river divides Oregon and Washington

The area and land of the gorge have been created over eons through a history of volcanic eruptions, floods, and landslides. The formation of the gorge we see today began around 40 to 60 million years ago when molten lava pushed up the granite to create the Columbia Basin. 

6 to 17 million years ago, volcanoes erupted, causing more than 20 basalt flows into the area, forming layers of rock up to 2,000 feet thick that makeup today's gorge. These layers of basalt are arranged in horizontal sheets called basalt flows. Two of the basalt formations are columnar basalt and cuboidal basalt. Columnar basalt is formed when lava cools slowly and evenly. These cracks form hexagonal patterns. Cuboidal basalt forms when lava cools rapidly and unevenly with the rocks created in an angular pattern. 

Then, glacial ice floods carve the canyon into a gorge. Around 40 of the Missoula, which are the largest floods within the last 2 million years. The floods then transformed the tributaries into the largest concentration of waterfalls, including the 620 ft. tall Multnomah Falls, the largest fall in Oregon and the second largest in the United States.