Compared to larger stratovolcanoes in the Cascade volcanic arc, Mount Washington, like the rest of Oregon's Matterhorns, had a relatively short eruptive life. Several spatter cones produced basaltic andesite on the lower northeastern side of the volcano, following a fissure that reached from Washington's summit. There were no lava flows from this eruption, nor at an eruption at the nearby Blue Lake Crater, which produced volcanic material that displayed petrographic similarities to the Mount Washington splatter cone deposits. These include similar porphyritic textures with 10 to 15 percent plagioclase phenocrysts as well as similar alignments, suggesting that they erupted simultaneously. Sherrod et al. (2004) argue that the spatter cones and activity from Blue Lake Crater represent the most recent eruptions near the McKenzie Pass and Santiam Pass region.