Lassen Volcanic National Park
Visit this highly under-rated active volcano in northern California!
Why Visit Lassen?
Before St. Helens there was Mt. Lassen, the last volcano to erupt in the Cascades. It erupted several times in 1914 - 1917 in spectacular fashion. The "lower 48" states would not see another eruption until St. Helens 63 years later.
Not only is it young, Lassen is by far the most accessible of all the Cascades volcanoes. Oh sure, you can drive to visitors centers on the flanks of Rainier, and stare into St. Helens' gaping maw from Johnston Ridge, but the Park Service (and Nature) keep you pretty far from the peaks where the action is. And just try to get close to Shasta, Adams, or Hood's peaks if you're an average person! At Lassen, a good road takes you to within a horizontal mile and 2100 vertical feet of the peak, and a well-built trail takes you the rest of the way!
The park also features beautiful old-growth forest that includes gigantic ponderosa pines, California red fir, mountain hemlock, white fir, and others. Hot springs dot the landscape. There's even a bubbling mudpot like the ones in Yellowstone. 300 years ago, the north side of the volcano collapsed in a gigantic landslide that is still easy to pick out, and Lassen is surrounded by smaller volcanoes for dozens of miles in every direction -- there's a lot to see!
Visiting Lassen
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Interactive map
Location: Lassen Volcanic National Park is located in far northern California east of the towns of Redding and Red Bluff. It's about 2:45 hours' drive north of Sacramento, and about 2:30 northwest from Reno, Nevada.
Vehicle: Any. Even the winding road up the peak is suitable for RV's, although you should be sure your brakes and cooling system are in good enough shape to tackle a serious mountain road. Fill your tank before leaving Red Bluff or Redding, as gas is quite expensive near the park.
Seasons: Summer to early fall. Lassen receives more snow than any other place in California, averaging 660 inches (1676 cm)! That means the snow lasts long into May and June. The main park road is closed in winter.
Lodging: The park offers very good campgrounds, and motels and cabins are available at Mineral (SW entrance) and Hat Creek (north entrance). There are a few cabins available at Manzanita Lake near the north entrance.
Hiking: The park has over 150 miles of trails at all ability levels. I highly recommend hiking the Lassen Peak trail to the top! The day I was there, I saw ages from 7 to 70 on the trail. See the park maps HERE.
Visit the park's website HERE.
About the Volcano
Lassen is one of -- if not the -- largest lava dome volcanoes in the world! (Sources are not unanimous on this). A lava dome forms when the lava being extruded from the ground is too viscous (thick) to flow; it just piles up higher and higher like Play-Doh being squeezed out of that little plastic mold. Lava domes are common in and around stratovolcanoes -- they're present at nearby Shasta, and St. Helens' crater is being filled by lava domes (last eruption in 2008), but Lassen is unique in being made entirely of lava domes.
Also see my volcano primer HERE for definitions and volcano information.
Because the lava is so thick, however, lava domes are extremely dangerous. If the magma/lava contains volatiles (gases) and depressurizes very quickly as it reaches the surface, the expansion of gases causes the magma to explode. It's exactly like shaking a soda can and popping the top, except this soda can is the size of a mountain! And besides explosions, lava domes create high, unstable rock piles that tend to collapse, sometimes long after they form. For example, the northwestern part of Lassen is called Chaos Crags, a complex of lava domes that formed about 1100 years ago and collapsed in a massive landslide/avalanche about 300 years ago.
Inside the north entrance is Chaos Crags, young lava domes that collapsed in a spectacular landslide that is still easy to spot. The park has more well-done, informative geological signs than most national parks, in my humble opinion.
The avalanche/landslide from Chaos Crags is easy to see, once you know to look for the jumbled rocks and boulders. The park road goes right through it.
If ever a geologic feature had the perfect name, it's Chaos Jumbles!
Lassen was created on the north side of an older, much larger volcano called Tehama that ceased activity about 300,000 years ago. Prominent Brokoff Mountain (a great name for a volcano if there ever was one!) west of Lassen is a remnant of Tehama.
The 20th Century Eruptions
Lassen awoke on May 30, 1914 after 27,000 years of sparse activity. A series of steam explosions occurred over the next 11 months as rising magma encountered groundwater in the mountain. Then in May of 1915, a lava dome appeared at the summit, sending glowing blocks down the mountain's flanks.
On May 19, 1915 gases in the lava dome decompressed violently, exploding the lava dome and sending molten-hot boulders down the mountainside. Over 30 feet of snow lay on the slopes, which raced down the northeastern slopes in a half-mile wide avalanche. Melting and picking up massive amounts of mud, the avalanche became a lahar -- a volcanic mudflow. The lahar devastated everything downstream as far as Old Station and Hat Creek, then continued as a muddy flood more than 30 miles downstream.
Photo of the May 19, 1915 eruption by B.F. Loomis. You can see the movie he made of the eruption at YouTube. Loomis was later instrumental in declaring Lassen a national park. Photo in the Loomis visitor center.
Photo from the park visitor center.
On May 22, 1915 the biggest eruption occurred when the rising lava dome again exploded, this time sending a column of ash (pulverized rock) 30,000 feet into the air. Part of the eruption column collapsed back down onto the mountain, sending millions of tons of hot rock and toxic gases rushing down the northeastern slope in a pyroclastic flow that covered more than 3 square miles. This area is called the "devastated area" today. Ash fell as far away as Elko, Nevada, 280 miles to the east.
Photo of the May 22, 1915 eruption in the park visitor center.
Lassen continued to rumble a bit until 1917. It will come to life again some day as evidenced by the continuing steam vents, hot springs, and mud pots, but there is no way to know exactly when.
The ash from the 1915 pyroclastic flow and airfall in the "devastated area" looks like sand. Forest covers much of it now.
You can identify the area devastated by lahars, pyroclastic flows, and ash airfall by the loose, sandy soil. That's the ash. The very rocky areas down in the drainage are lahar debris.
Lassen Volcano
Lassen is different from other Cascades volcanoes in appearance, especially from a distance. It's surrounded by the still-high remnants of ancient volcano Tehama, so that from a distance it can be hard to know which peak is Lassen. This photo is from the SW entrance road. I'd characterize Lassen from this side as being the one that looks like your bald Uncle Mel's hairline. It's also the last one to have snow on it in late summer.
Lake Helen is definitely the best place to get pictures of the peak. It's named after the first woman to summit Lassen, Helen Tanner Brodt, who climbed it in 1864. The supernaturally clear waters made my artist wife grab the camera from me! In fact, she took this picture.
Lassen is a conglomeration of lava domes. They are characterized by steeply inclined foliation, or layering like this fractured road cut by Lake Helen. The foliation forms while the magma is flowing upward through fractures. Because they crystallized rather quickly in the shallow ground, they are not quite as coarsely crystalline as a typical granite, yet not as fine-grained as an extruded volcanic rock.
To me, the major attraction at this national park is the Lassen Peak trail, the start of which is shown here. There is no other trail in the Cascades that compares to it in ease and accessibility. It's the only trail to a major volcano's summit that the average person can do! It's only 5 miles round-trip and a 2000 foot elevation gain, and the trail is easy on the feet. It takes off from a generous parking lot at the 8500 foot summit of the park's main road -- you won't miss it. Learn more from the park's website here.
You can see a good foliation by the peak trail parking lot. That's Lassen Peak in the background, with its lava domes forming cliffs. The conspicuous feature in the cliff is called "Vulcan's Eye," a piece of hardened lava carried along by the rising lava dome.
Up close, you can see how the minerals and magma were stretched and kneaded into this foliation. The rock type of most of Lassen is dacite (see my favorite online geologic glossary from Oregon State HERE), which is chemically between rhyolite and andesite. It's the same type of rock of St. Helens' recent eruptions. Also see my volcano primer HERE for explanations and terminology.
Poster at the trailhead, showing the Lassen Peak trail. With binoculars, you can see the switchbacks up the ridge from the parking lot. The trail was extensively reconstructed just a few years ago, and it shows -- good retaining walls, steps where helpful, and a wide, level path. It's the Interstate Freeway of trails!
Rock Spotting 1: Watch for the volcanic ash (which looks like sand), rhyolite (nearly white rocks, often containing pumice), and dacite (darker colors, often with some visible white mineral crystals). The rocks erupted in 1915 originated from mixing of various types of magma. For an excellent technical summary of the Lassen volcanic rocks, see the Journal of Petrology -- they're actually quite complex in origin and compositions!
Rock Spotting 2: Watch for this boulder, which contains pieces of other magmas caught in the lava dome. It's about 2 meters long.
Rock Spotting 3: Watch for this basalt boulder in a retaining wall that has vesicles (gas bubbles, in this case tube-shaped) and pahoehoe (ropey) flow texture on top. These rocks were obviously hauled in from elsewhere to build retaining walls.
View from the trail back down toward Lake Helen. The views from the trail are so constantly spectacular, it would just be easier to mount a Go-Pro to your head and record the whole thing, but no one would want to watch it with you!
The trail has a good, level surface and well-done retaining walls to preserve and protect it. Good job, trail crews!
The trailhead parking lot is left of center, and that's Lake Helen in the center. This area is made of crumbly lava domes.
The far peak is Brokoff Mountain, a remnant of ancient volcano Tehama. It's the first peak you see when driving in the SW entrance. The peaks in this picture are remnants of Tehama's northern edge.
Even in a draught year and mid-August, I encountered snow drifts! Lassen gets more snow than any other place in California, and that's in a field with plenty of stiff competition! The mid-summer snow makes this a refreshing summer hike.
These pieces of lava dome are brecciated, which means "made of broken pieces." Breccia often forms around the dome edges where the magma is cool enough to be brittle while the whole mass is still flowing.
Up close, you can see that all the pieces are made of the same lava/magma, they just broke into pieces while flowing.
Rock Spotting 4: Find this window in the lava dome breccia!
Near the top, you'll see big rocks thrown out by the 1915 eruptions, like this sharp boulder sitting on lava dome rubble.
This sign is along the trail where the dark 1915 dacite rocks become common. The black color is unusual for dacite, which is commonly light to medium gray.
The trail's summit. You'll be so happy to see this! You've reached the top! No more uphill! The signs explain what you can see in various directions. Notice that the highest peak of Lassen is a little farther along. It's not a hard climb, but not exactly easy, either.
Here's a view of Shasta looking across Lassen's 1915 crater and domes. Shasta is about 4000 feet higher than Lassen, and is a very challenging climb.
The 1914 and 1915 eruptions of Lassen created first a couple of small craters and then this jumble of lava dome debris. All lavas contract and fracture when they cool, so lava domes crumble into jumbled masses like this. You'll see some footpaths that skirt the deepest fissures and sharpest rocks -- take them! The rocks and the views are worth the small extra effort.
Shasta is an irresistible photo subject! This is across the NE slopes of the summit domes.
You couldn't have stood here in 1915 because this was the source of the catastrophic eruptions. The "devastated area" appears light-colored in this picture, but much of the young forest for a couple of miles out was also covered by the lahars and pyroclastic flows.
A closer view of the devastated area.
The Cascades' second youngest volcanic eruption is worth one more pic!
The summit crater is probably best visited in late summer and before Fall snows, when the drifts are at their minimums. See if you can distinguish the lava dome debris from the rocks that fell from the sky in explosions.
Here's a close view of the unique 1915 black dacite. The white minerals are plagioclase feldspar, one of Earth's most common minerals.
Here's a view of the trail switchbacking its way down the ridge. Bet you didn't know "switchbacking" was a verb! It is now! That's Lake Helen out there.
Here's another picture of the trail, and another chance to use the word "switchbacking." There's a whole lot of switchbackiness going on here!
On this particular day the distant valley air had a lot of wildfire smoke, which is common in the late summer.
Volcanic rocks are often colored in reds, oranges, and yellows by acidic hydrothermal waters associated with the magma. Prospectors like to dig into these (outside the national park!) because they can contain valuable metal ores.
Lassen's lava domes rose along fractures associated with the older volcano, Tehama. This view to the west shows Brokoff Mountain, the most prominant remnant of Tehama. It's common for a volcano to rise at the edges of an older one. Another example in my field trips is Vesuvius in Italy, which grew inside of the older Mount Somma.
Rock, snow, shadows.
Glacial striations on Lassen's dacite. The entire high peaks were covered in ice during the last ice ages, which ended about 12,000 years ago. Glaciers freeze the rocks below them into the ice and drag them downhill, scratching and polishing the bedrock below.
Hydrothermal Features
Stop to see the hot springs and mud pot between the SW entrance and Lake Helen. In this wide view, you can see that the hot springs have created light-colored deposits and alteration over a wide area.
Volcanic activity is the source of a lot of economic minerals including (in the right situations) sulphur, iron, magnesium, copper, silver, gold, and chrome. The sign's warnings are real -- never walk off path in a hydrothermal area! Yellowstone even has a webpage about the dangers here.
Mud pots aren't just for Yellowstone! The mud is feldspar minerals that have been dissolved by acidic hydrothermal waters into clay.
Lassen has several hydrothermal features, the largest of which is the curiously named "Bumpass Hell." The Supans springs and mudpot are nearest the center of ancient Tehama volcano, and are right along the park road. The source of heat is leftovers from Tehama and Lassen activity -- rock down several thousand feet can stay hot for a million years or more.
SW Entrance
The Kohm Yah-Mah-Nee Visitor Center is surrounded by gorgeous old-growth forest, and features a great view of Lassen from its back yard. It's just inside the SW entrance.
I try to stick to geology, but I love spectacular trees like this huge red fir. And don't get me started with Redwoods and Sequoia parks!
Lassen features a unique mixed-conifer forest that will take your breath away! The park service has a nice guide to Lassen's trees here.
The southwest entrance is accessible from Red Bluff via highway 36. The north entrance is accessible from Redding via highway 44 or from Shasta City via highway 89 and 44 -- a gorgeous route that also takes you by the stunning Burney Falls (field trip coming soon).
View of Lassen (left) and Brokoff Mountain from the road to Red Bluff. In the foreground is boulder remnants of a large, local basalt lava flow. The mound around Lassen gives a clue as to Tehama's enormous size.
View to the west of two volcanoes near Red Bluff. Lassen is in the middle of a large region of abundant young volcanoes and potential future eruptions.
A smoky summer sunset over the northern Coast Ranges west of Lassen, with a rubbly basalt lava flow in the foreground.
Related field trips: Rainier: Paradise, Rainier: Sunrise, Shasta, Crater Lake, St. Helens
