7.6: Lassen Volcanic National Park

A Natural Volcanology Classroom

Lassen Volcanic National Park (Figure \(\PageIndex{1}\)) began as two separate national monuments designated by President Theodore Roosevelt in 1907: Cinder Cone National Monument and Lassen Peak National Monument. Beginning in 1914, Lassen Peak gained the interest of the nation during a series of volcanic eruptions, and the National Park was established on August 9, 1916. While Lassen Volcanic Lassen National Park remains one of the least visited U.S. National Parks visited annually, it remains one of the most geologically and historically interesting parks in the National Park System.

Figure \(\PageIndex{1}\): Map of Lassen area showing hydrothermal features (red dots) and volcanic features or remnants (yellow cones). Also shown is the outline of Brokeoff Volcano. "Lassen VNP Map" by Emily Wright is licensed under CC BY-NC-SA 4.0 and is a derivative of the original by the USGS, which is in the public domain. Access a detailed description.

Long before its designation as a National Park, at least four Native American Indian groups used the Lassen area as a meeting point. The area was not conducive to year-round living due to snow conditions, high elevation, and migrating deer populations, but the Atsugewi, Yana, Yahi, and Mountain Maidu people camped, hunted, and gathered there during the warmer months.

Lassen Volcanic National park is unique in that it includes examples of four types of volcanoes: shield, composite volcano, cinder cone, and lava dome (see 7.3: The Variety of Volcanoes in the Cascades and the Modoc Plateau-Figure \(\PageIndex{2}\)). Lassen peak is one of the world’s largest lava dome volcanoes, but the 3,187 m (10,457 ft) tall volcano sits on the north-east flank of the remains of Mount Tehama, a composite volcano. Numerous other lava domes surround Lassen Peak and many cinder cones dot the landscape in the eastern part of the park, including the creatively named Cinder Cone. There are four shield volcanoes in the park; Mount Harkness (southwest corner of the park), Red Mountain (at south-central boundary), Prospect Peak (in northeast corner) (Figure \(\PageIndex{3}\)), and Raker Peak (north of Lassen Peak). They range in elevation from 2,133–2,560 meters (7,000–8,400 feet) above sea level and each is topped by a cinder cone volcano.

Figure \(\PageIndex{2}\): Shaded Relief Map of Lassen Volcanic National Park labeled with the name and type of volcanoes. "Map view with feature labels" by the National Park Service is in the public domain. Access a detailed description.

Figure \(\PageIndex{3}\): Four primary types of volcanoes occur within the park: composite volcano (upper left; Brokeoff Mountain, which is a remnant of Brokeoff Volcano), cinder cone (upper right; Cinder Cone; in the background is the Lassen Peak lava dome), shield volcano (lower left; Prospect Peak), and lava dome (lower right; the domes of Chaos Crags). Photographs by Michael A. Clynne (upper and lower left) and Patrick Muffler (upper and lower right). "Four Types of Volcanoes" by USGS is in the public domain.

In earlier activities in this chapter, you identified both the type of rock and the type of volcano at Chaos Crags in Lassen Volcanic National Park. Now, put these concepts together and review what you learned about magma viscosity in section 7.3: The Variety of Volcanoes in the Cascades and the Modoc Plateau in the activity “Chaos Crags: Putting it all Together”.

Query \(\PageIndex{1}\)

The Missing Volcano: Mount Tehama

When students learn to recognize composite volcanoes, they are taught to picture iconic summits, like Mount Fuji in Japan or Mounts Shasta and Rainier in the Cascade Range. Unlike the other three general types of volcanoes (cinder cones, shield volcanoes, and lava domes), a representative of this type of volcano is not currently easily recognizable in Lassen Volcanic National Park. Once upon a time, however, an impressive composite volcano, Mount Tehama, also known as Brokeoff Volcano existed. It consisted of lava domes, lava flows, and pyroclastic deposits that are between 590,000 and 385,000 years old. In its heyday, Mount Tehama would have been around 300 meters (a thousand feet) higher than Lassen Peak is today, and was 20 km (12 miles) wide at its base. This volcano was eroded, primarily by glaciers, so that only remnants remain. The surviving portions of the central rim include Brokeoff Mountain, Mount Diller, Mount Conrad, and Pilot Pinnacle. Figure \(\PageIndex{4}\) shows an outline of the projected original shape of Mount Tehama (Brokeoff Volcano) with Lassen Peak in the background for comparison.

Figure \(\PageIndex{4}\): Projected profile of Brokeoff Volcano which would have risen to an elevation of 11,000 ft (3300, m). Lassen Peak is visible behind the former Brokeoff Volcano. "Projected profile" by Michael A. Clynne, USGS is in the public domain. Access a detailed description.

The 1914-1917 Eruption of Lassen Peak

On May 22, 1915, a large explosive eruption at the summit of Lassen Peak, California devastated nearby areas and rained volcanic ash as far away as 280 miles to the east. This explosion was the most powerful in a series of eruptions during 1914–17 that were the last to occur in the Cascade Range before the 1980 eruption of Mount St. Helens, Washington.

The 1914–17 eruptions of Lassen Peak were among the first volcanic events to occur after photography became readily available to amateurs. Thus, they were documented and popularized by the northern California media, primarily the San Francisco Chronicle, and subsequently by the popular scientific media. The photographs of amateur photographers, particularly those of Benjamin Franklin Loomis (1857–1935) proved crucial to understanding the chronology and processes of the May 1915 eruptions. Some eruptive events were even caught on film by Red Bluff resident J.J. Hammer.

Video \(\PageIndex{1}\): Mt Lassen 1915

“Mt Lassen 1915” shows the film by J.J. Hammer. The original film was silent and the YouTube version includes only added film reel sound effects, but no relevant audio.

Initial Rumblings

On May 30, 1914, Lassen Peak awoke from a 27,000-year-long slumber when it was shaken by a steam explosion. Such steam blasts occur when molten rock (magma) rises toward the surface of a volcano and heats shallow groundwater. The hot water then rises under pressure through cracks and, on nearing the surface, vaporizes and may vent explosively. That first explosion created a small crater at the summit of Lassen Peak, and each of more than 180 subsequent steam explosions enlarged it (Figure \(\PageIndex{5}\)). Over more than 11 months, these steam explosions blasted out a crater 1,000 feet (300 m) long.

In mid-May 1915, the character of the eruption changed dramatically. On the evening of May 14, 1915, incandescent blocks of lava could be seen bouncing down the flanks of Lassen Peak from as far away as Manton, 20 miles (32 km) to the west. By the next morning, a growing dome of dacitic lava had welled up and filled the crater at the summit of Lassen Peak.

Figure \(\PageIndex{5}\): A steam-explosion eruption at Lassen Peak on June 14, 1914. Such steam-blast eruptions ranged from a few minutes to several hours in duration and often sent plumes thousands of feet above the volcano. Photograph taken by B.F. Loomis from a point west of Manzanita Lake, about 6 miles (10 km) from Lassen Peak. This photograph, made available by the National Park Service, is in the public domain.

Events of May 19–20, 1915

On the evening of May 19, a large explosion shattered the still-hot lava dome that had filled Lassen’s summit crater during the previous week, blasting out a new crater at the volcano’s summit and creating an avalanche of hot lava blocks, volcanic debris, and snow. As the snow melted, a huge lahar rushed 18 km (11 miles) down Lost Creek, releasing huge volumes of water and flooding lower Hat Creek Valley. The avalanche, lahars, and floods produced by this explosion uprooted and carried away trees 30 m (100 feet) tall with ease and damaged several ranch houses. During that night (May 19–20), lava welled up into the crater created by the explosion, overflowed the summit depression, and fed two lobes that flowed about 300 m (1,000 feet) down the northeast and west flanks of the mountain.

Climactic Event of May 22, 1915

On May 22, Lassen Peak exploded again in a powerful climactic eruption that blasted rock fragments and pumice high into the air, creating the larger and deeper of the two craters seen at the summit of the volcano today and generating a vertical eruption column that rose to 10,000 m (30,000 feet; Figure \(\PageIndex{6}\)). Partial collapse of the eruption column generated a pyroclastic flow that swept down the northeast side of the volcano. Trees still standing after the May 19 eruption were now blown down. The pyroclastic flow rapidly melted snow in its path, creating a lahar that followed the path of the lahar two days earlier and rushed down Lost and Hat Creeks to Old Station, releasing water that again flooded lower Hat Creek Valley.

Figure \(\PageIndex{6}\): Lassen Peak in northern California produced a series of eruptions during 1914–17. The largest of those eruptions, on May 22, 1915, blasted rock fragments and pumice high into the air and rained fine volcanic ash as far away as Elko, Nevada, 280 miles (450 km) to the east. This photograph, taken from the town of Red Bluff, 40 miles (65 km) west of the volcano, shows the huge eruption column of ash and gas, which rose to a height of more than 30,000 feet (9,000 m). This photograph, by R.E. Stinson, has been made available by the National Park Service and is in the public domain.

Continued Volcanic Activity and Future Eruptions

For several years after the eruption of May 22, 1915, snowmelt percolating down into Lassen Peak, especially in the spring, triggered steam explosions, indicating that rocks beneath the volcano’s surface remained hot. Particularly vigorous steam explosions in May 1917 blasted out the northern of the two craters now seen at the volcano’s summit. Steam vents could still be found in these craters into the 1950s, but they gradually weakened and are difficult to locate today.

Figure \(\PageIndex{7}\) shows the extent of the deposits from the May 1915 eruptions of Lassen Peak. The total volume of the 1915 eruptions was approximately 0.03 km3 (0.007 cubic mile)—tiny compared to a major eruption like that of Mount St. Helens in 1980 (1 km3 or 0.24 cubic mile). The deposits from the Lassen Peak eruptions are rapidly becoming obscured by vegetation and erosion (Figure \(\PageIndex{8}\)), and the small size and unconsolidated nature of the thin deposits make the 1915 eruptions unlikely to be preserved in the long-term geologic record. Today, Lassen Peak sleeps again, but active steam vents, hot springs, and bubbling mud pots are still found elsewhere in Lassen Volcanic National Park. No one can say when, but it is almost certain that the Lassen area will experience volcanic eruptions again. The USGS California Volcano Observatory operates a sophisticated sensor network to detect any increase in seismicity, ground deformation, or gas emissions that could indicate magma rising toward the surface in preparation for the next Lassen eruption. Early detection of such eruption precursors is essential to effective hazard mitigation and forecasting.

Figure \(\PageIndex{7}\): This generalized geologic map shows Lassen Peak and the deposits from its May 1915 eruptions. Those eruptions destroyed an area of 3 square miles (7.7 km2 ), now called the Devastated Area, on the northeast flank of the volcano. "Deposits from Lassen Peak’s May 1915 Eruptions" by USGS is in the public domain. Access a detailed description.

Figure \(\PageIndex{8}\): Sequence of photographs taken before and after the cataclysmic eruptions of Lassen Peak in May 1915. The first image in the sequence shows a view of the northeast flank of Lassen Peak taken before 1914. Mature conifer forest covers the lower slopes. The next photo was taken at noon on May 22, 1915, showing the destruction from the avalanche and lahar of May 19–20. Trees 30 m (100 feet) tall were uprooted and carried away with ease. The large rock in the foreground, labeled “hot rock” by Loomis, is a piece of the lava dome that filled the crater during the previous week that was carried down by the avalanche. Note the remaining tree-covered slopes at the left and right margins of the avalanche path and the dark gray tongue of new dacite lava below the volcano’s summit that erupted on the night of May 19–20. The third image is a view of Lassen Peak’s northeast flank taken in June 1915, showing the full devastation caused by the cataclysmic explosive eruption of May 22. Trees still standing on the morning of that day were blown down or snapped off and their trunks left lying on the ground, pointing away from Lassen Peak. The lava flow below the summit is gone, and the May 22 mudflows have smoothed the surface of the May 19 avalanche and lahar deposit. The “hot rock” remains—and can still be seen today on the Devastated Area Interpretive Trail, as seen in the fourth image taken in 2023. The appearance of the Devastated Area changed little for 50 years as seedlings struggled to gain a foothold. Today, however, young vigorously growing trees are obscuring the devastation and reclaiming the area as forest. The first three photos by B.F. Loomis, published by the USGS, are in the public domain. The final photo was taken by Emily Wright, who also compiled this figure, which is licensed under CC BY-NC-SA 4.0.

Hydrothermal Activity in Lassen National Park

Today, the active volcanism at Lassen Volcanic National Park still produces remarkable hydrothermal features, including fumaroles, mud pots, boiling pools, and thermal ground. These are very active most of the time, emitting hydrogen sulfide (H2S) and coating rocks with yellow sulfur deposits.

Water enters the Lassen hydrothermal system at high elevations, when water from rain and snow percolates into the subsurface and is heated by hot rock surrounding a magma chamber 8-10 km (5-6 mi) below the surface. The water penetrates the rock surrounding the heat source and is heated by conduction. Hydrochloric acid, sulfurous gasses, and other volatiles emitted by the body of magma or the hot rock dissolve in the water as it is heated. Because it is less dense than cold water, the heated water rises by convection. As the water rises, acids react with surrounding rock, enriching the water in dissolved silica (SiO2) and metals. Hot water eventually reaches low enough pressures to boil in the vapor-dominated zone. Steam and gasses are released to surface fumaroles and acidic hot springs. Residual thermal water flows down gradient and emerges as hot springs and geysers south of the park (Figure \(\PageIndex{9}\)). In active hydrothermal areas, hot water enriched in dissolved metals and other chemicals evaporates. This leaves behind colorful sulfate minerals like the yellow copiapite (hydrous iron sulfate) and black or brassy pyrite (iron sulfide or fool’s gold). Algal and bacterial mats also contribute to the colorful display of the hot springs.

Figure \(\PageIndex{9}\): Recharge of the Lassen hydrothermal system begins at high elevations. Water from rain and snow percolates into the subsurface and is heated by hot rock surrounding a magma chamber 8-10 km (5-6 mi) below the surface. Hot water rises via convection. Hot water eventually reaches low enough pressures to boil in the vapor-dominated zone. Steam and gasses are released to surface fumaroles and acidic hot springs. Residual thermal water flows down gradient and emerges as hot springs and geysers south of the park. This Graphic by Trista Thornberry-Ehrlich, Colorado State University, is published by the USGS and is in the public domain. Access a detailed description.

Perhaps the most famous of these hydrothermal areas is Bumpass Hell (Figure \(\PageIndex{10}\)), which marks the principal area of upflow and steam discharge from the Lassen hydrothermal system. The area was named for a miner Kendall Vanhook Bumpass who was the first European settler to visit in the 1860s. On his second trip to the boiling mud pots, he broke through the thin crust and scalded his leg so badly it required amputation. Hydrothermal features like Bumpas Hell are indicators of the ongoing potential for future volcanic eruptions in the Lassen volcanic center.

Figure \(\PageIndex{10}\): “Bumpass Hell” by Don DeBold via Flickr is licensed under CC BY 2.0.

Video \(\PageIndex{2}\): Hiking Bumpass Hell

If you are interested in learning more about Bumpass Hell, watch this video field guide by the National Park Service.

Cinder Cone and the Fantastic Lava Beds

Many small cinder cones throughout the southeastern Cascades and Modoc Plateau are unnamed. Others have unoriginal names like Black Butte or Red Cinder Cone (not to be confused with the distinctly more cone-shaped Red Cinder about a half-mile to the east). Perhaps the least originally named of all is Cinder Cone in Lassen National Park (Figure \(\PageIndex{11}\)). This classically shaped, relatively young cinder cone in a National Park makes an excellent case study of a typical Cascade cinder cone.

Figure \(\PageIndex{11}\): Author Emily Wright prepares to ascend Cinder Cone. Photo by Micah Wright is licensed under CC BY-NC-SA 4.0.

The hike up Cinder Cone (258 m or 846 ft) starts with a broad path skirting the edge of the Fantastic Lava Beds (see the Box: Fantastic Lava Beds). The pumice-y soil makes walking a bit strenuous despite the gentle slope in this early part of the trail. The contrast between the mature forest on the right and the very young-looking lava flow on the left is striking. The youthful appearance of the lava flow deceived early explorers of Lassen. In 1875, H.W. Harkness described Cinder Cone as probably being no more than 25 years old. Geologists now know that Cinder Cone erupted in 1666, so it would have then been around 200 years old when Harkness described it. Geologically speaking, that’s still very young!

There is a distinct change in character of the trail as you start up the Cinder Cone itself. The steep angle of the trail in the loose scoria makes the climb to the summit quite arduous, but the views are well worth the effort. At the summit, the double rimmed crater is visible (Figure \(\PageIndex{12}\)). The double rim was probably created by fluctuating eruptive activity late in the formation of the cone. There are also good views of the several blocky lava flows associated with Cinder Cone. To the casual observer and even to some of the first geologists to study Cinder Cone, there appear to be multiple ages of lava flow. The soft, sand-dune-like appearance of the Painted Dunes Lava Flow makes it seem much more weathered than the sharp, dark, Fantastic Lava Beds (Figure \(\PageIndex{13}\)). However, geologists have now shown that the entire eruptive sequence at Cinder Cone represents a single continuous event that probably spanned no more than a few months. During this event, the composition of the molten rock (magma) feeding the eruption changed from basaltic andesite to andesite and then back to basaltic andesite, but with a higher titanium content. Two cones erupted over the course of this event. The remnants of a nearly completely buried earlier cone can be seen on the larger cone’s south side. Much of the earlier cone was probably destroyed by lava flows erupting from its base. The weathered look of the Painted Dunes flow is actually the result of ash falling onto still-hot lava from an earlier phase of the eruption. The ash is brightly oxidized because it fell on the lava flows when they were still hot, giving the dunes their “painted” look.

Figure \(\PageIndex{12}\): Double rim of Cinder Cone. Photo by Emily Wright is licensed under CC BY-NC-SA 4.0.

Figure \(\PageIndex{13}\): View of the Painted Dunes and Fantastic Lava Flow from the summit of Cinder Cone. "Painted Dunes as seen from Cinder Cone" by Ilja Klutman is licensed under CC BY-NC-SA 2.0.

Video \(\PageIndex{3}\): Lassen Volcanic National Park | Cinder Cone Trail | the Best View of Mt. Lassen in California

For video footage of the hike described in the previous paragraphs, complete with summit views, watch the video. There is no audio narration for this video, only music.

Acknowledgments

Parts of the text on this page were taken with minimal editing from sources provided by the USGS and the National Park Service, which are in the public domain. Links to the original text can be found in the reference section on this page.

References

1. Clynne, M. A. (2011). Stratigraphy and compositional evolution of Cinder Cone, a composite monogenetic cone in Lassen Volcanic National Park, California. 2011, V13C-2621.
2. Clynne, M. A., Champion, D. E., Trimble, D. A., Hendley II, J. W., & Stauffer, P. H. (2000). How Old is “Cinder Cone”?—Solving a Mystery in Lassen Volcanic Park, California [Fact Sheet 023-00]. US Geological Survey. https://pubs.usgs.gov/publication/fs02300
3. Clynne, M. A., Christiansen, R. L., Stauffer, P. H., Hendley II, J. W., & Bleick, H. A. (2014). A sight" fearfully grand": Eruptions of Lassen Peak, California, 1914 to 1917. US Geological Survey. https://pubs.usgs.gov/publication/fs20143119
4. Clynne, M. A., Janik, C. J., & Muffler, L. J. P. (2003). “Hot Water” in Lassen Volcanic National Park—Fumaroles, Steaming Ground, and Boiling Mudpots (Fact Sheet 101-02). US Geological Survey. https://pubs.er.usgs.gov/publication/fs10102
5. Clynne, M., & Muffler, L. (2010). Geologic Map of Lassen Volcanic National Park and Vicinity, California: U.S. Geological Survey Scientific Investigations Map 2899 [Map]. https://pubs.usgs.gov/sim/2899/
6. KellerLynn, K. (2014). Lassen Volcanic National Park: Geologic Resources Inventory Report (NPS/NRSS/GRD/NRR—2014/755). US National Park Service. https://irma.nps.gov/DataStore/DownloadFile/489001
7. Klemetti, E. (2016, February 17). Watch One of the First Volcanic Eruptions Ever Filmed. Wired. https://www.wired.com/2016/02/watch-one-of-the-first-volcanic-eruptions-ever-filmed/
8. Loomis, B. F. (1926). Pictorial History of the Lassen Volcano. California Press.
9. Szymanski, M. E., & Teasdale, R. (2015). Groundmass Crystallinities of Proximal and Distal Lavas from Cinder Cone, Lassen Volcanic Field. AGU Fall Meeting Abstracts, 2015, V23B-3106. https://ui.adsabs.harvard.edu/abs/2015AGUFM.V23B3106S/abstract
10. U.S. National Park Service. (2023, April 17). Volcanic Resources Summary—Lassen Volcanic National Park. https://www.nps.gov/articles/000/volcanic-resources-summary-lassen-volcanic-national-park.htm