Mount Lassen: Last but not Least!

Cover photo by imtnbike.

Most people in California don’t think much about Mount Lassen. You can only kind of see it as you drive up Interstate 5, Mount Shasta is bigger and more impressive and Mount Saint Helens looms large in our minds as the last huge volcanic eruption in the Cascade Range (1980). But Mount Lassen should not be forgotten!

It had a large eruption on May 14, 1914; ash was lifted 30,000 feet into the sky and a huge ash plume swept down the flanks of the mountain leveling everything in a 3 square mile area. Called the “Devastated Area” you can go there today and clearly see the line between the old forest and the “pyroclastic flow.” Mount Lassen quieted down by 1917 and has been largely inactive ever since, except for a small puff in 1921.

Mount Lassen is also noteworthy in that it is the last (or first depending on your north/south bias) active volcano in the Cascade Volcanic Arc, which stretches northward to British Columbia. These volcanoes exist because of oceanic plates that are actively being pushed underneath the continent of North America. The southern most plate (the Gorda) starts going under, or subducting, just south of Eureka. If you look at a map of California and go due east from Eureka, you see Mount Lassen! A clear connection between subduction and volcanic activity. Pretty cool!