This maps shows what is likely if, and when, an eruption occurs within the Lassen Volcanic Center. The tan area that dominates a major portion of Lassen Volcanic National Park shows where lava domes and flows could originate. The wide pink circular line around the area is where pyroclastic flow or lava flows could be expected to extend. Note that Mineral is within this area, and it extends almost to Chester. Red, orange and yellow areas indicate lahars. The outer dotted pink line is how far away volcanic ash would be expected to reach, if not further. Map by the USGS

Lassen Volcanic National Park’s threat a reality, but not in our lifetime

It’s not a matter of if the area around Lassen Volcanic Center will erupt in the future, but when.

That’s according to Dr. Michael Clynne, research geologist, and the most knowledgeable scientist on the Lassen Volcanic National Park area. “I’m the point person,” he said in a recent interview.

That doesn’t mean Clynne is encouraging residents to pack their bags or plan evacuation routes immediately. Although volcan

Research geologist Michael Clynne knows more about the Lassen Volcanic Complex than anyone else. He’s studied the area as part of his research during the last 40 years. This is Clynne taken a few years ago in the Lassen Peak area.
Photo by the U.S. Geological Survey

ic activity is somewhat unpredictable, scientists who watch volcanoes distinguish between earth time and human time. What could mean soon in earth time might be 1,000 years, a long time in terms of the human race.

New interest in potential activity at some of the Pacific coastal states’ volcanoes arose with the continuing activity at Hawaii’s Kilauea Volcano and more recent eruptions at the Fuego Volcano in Guatemala.

Three California volcanoes, including Mt. Shasta and Lassen Peak (also known as Mt. Lassen) and Long Valley Caldera near Mammoth, are listed at very high threat potential, according to scientists at the California Volcano Observatory in San Jose. CalVO is part of the U.S. Geological Survey’s Volcano Hazards Program, where Clynne is based.

These three volcanoes are part of an 800-mile stretch of the West Coast, including California, which contains 13 volcanoes.

The most recent to erupt in this chain is Mount St. Helens in 1980. Lassen Peak was the next most recent, when it erupted approximately 100 years ago. “Lassen Peak is the largest and youngest of a group of more than 30 volcanoes that have erupted in the Lassen Peak area over the past 300,000 years,” according to the web site Volcano Discovery.

Before its eruption, Lassen Peak was dormant for 27,000 years.

“The total volume of the 1915 eruptions was tiny compared to a major eruption like that of Mount St. Helens in 1980,” according to the USGS on the anniversary of Lassen Peak’s eruption May 22, 2015. Clynne agrees with that.

In comparison, ash was spread an estimated 280 miles away to Eastern Nevada during Lassen Peak’s largest eruption. Mount St. Helen’s impact was realized as far away as Minnesota.

 

 

What makes a volcano or volcanic area considered active? “Those definitions are not set in stone,” according to Volcano World from Oregon State University. “And they mean different things to different people.”

One of the most agreed upon definitions is that an active volcano is one that has erupted in the last 10,000 years, or since the last ice age.

A dormant volcano is one that hasn’t erupted in the last 10,000, years but is expected to erupt again sometime.

An extinct volcano is one that no one expects to ever erupt again.

Even then, there can be surprises.

In looking at the Lassen Volcanic Center, the summit is actually a complex that rises 2,000 feet above the surrounding area. Its volume is a half a cubic mile and it is considered one of the largest lava domes in the world, according to Volcano Discovery information. “Its summit is a complex area of several craters.”

According to information from the USGS on Lassen Volcanic National Park, the area was created by rising molten rock also known as magma. The magma is generated as the oceanic Juan de Fuca Plate, one of the tectonic plates making up the Earth’s outer shell, plunges beneath the continental North American Plate. The boundary between the plates is called the Cascadia Subduction Zone that dips eastward beneath the Pacific Northwest at an offshore trench.

The geology of the Lassen Volcanic Center is also influenced by stretching of the Earth’s crust, according to the USGS.

According to scientists, like Clynne, nearly all of the volcanic rocks in the Lassen Volcanic Center appeared in eruptions during the last three million years. For the center, that volcanic activity can be pinpointed to the formation of the Brokeoff stratovolcano, which occurred about 600,000 years ago.

Lassen Peak was formed about 27,000 years ago. Chaos Crags, a dome complex, is relatively new, coming about 1,100 years ago. The Cinder Cone erupted about 350 years ago.

It’s the hydrothermal features within Lassen Volcanic National Park that give evidence that it is an active volcano. Fumaroles that give off steam and volcanic-gas vents, mudpots, boiling pools and steaming ground are all part of the park’s active features.

The most active area within the park is Bumpass Hell. According to the USGS, Big Boiler is not only the largest fumarole in the park, but one of the hottest hydrothermal fumaroles in the world at 322 degrees F.

Steam vents and hot springs are surface expressions of hydrothermal systems, in which cold surface water percolates deep into the ground, where it is warmed by the slow release of thermal energy from a heat source,” according to scientists at the USGS. “The Lassen Volcanic Center is host to such a system because it has the three required elements — abundant ground water, permeable rock and a heat source at depth.”

 

Knowledge of Lassen area

Clynne began studying the Lassen Volcanic National Park as a young man. “I started working for the USGS between my junior and senior years in college as a field assistant for a graduate student,” he explained. “That job evolved into my own thesis work.”

For his master’s degree from California State University, San Jose, his thesis research was on geologic mapping of volcanoes and volcanic rocks in Lassen Park.

For his Ph.D., Clynne studied earth science at the University of California at Santa Cruz. His research focused on the origin and evolution of magma and volcanoes at Lassen Park.

Although Clynne’s experience involves the study of young volcanic rocks in volcanic arcs, primarily in the Cascade Range, “I have worked the greater Lassen area for 40 years and am the world’s expert on volcanism in the southern most Cascade Range.”

Although Clynne may be most at home in the Lassen volcanic area, 20 years ago his field shifted to Mount St. Helens. “I am working on understanding the pre-1980 eruptive history of the volcano,” he explained.

He’s also had temporary assignments at Cheju-do in South Korea and Alid volcano in Eritrea, Africa.

Given his background and knowledge of the Lassen Volcanic Center, when asked if he was disappointed that he probably wouldn’t see any part of Lassen erupt during his lifetime, Clynne said that wasn’t his area of expertise. As a research geologist, it’s his job to know what could happen during an event.

Based on evidence existing from past eruptions and the kind of volcanoes within Lassen complex, it’s his job to understand the impacts to the area and its residents.

When Lassen erupted from 1914 to 1917, very few people lived in the area. Areas affected or could be affected by an eruption have considerably more people today, Clynne said.

Infrastructure would be impacted, he said. Roads and highways would be covered with lava and other debris making travel difficult.

Air travel would also be changed. However, here on the West Coast, air routes to and from California airports could be easily changed. Aircraft would be rerouted around the steam and ash caused by an eruption. Delays or complete disruption wouldn’t occur as it has with other volcanic eruptions, such as the one in Iceland a few years ago.

“We study and monitor volcanoes with a goal of learning as much as we can to reduce the hazards of volcanoes to society,” Clynne said recently. “A secondary goal is to characterize the geothermal resource associated with the volcanoes and volcanic areas. A nice aspect of my job is that within the broad guidelines of the Volcano Hazards Program, I get to design and direct my research.”

As a research geologist, Clynne spends two to three months each summer in the field. “My days are spent on and near the volcano examining volcanic deposits and lava flows, interpreting their origin and collecting rock and other samples.”

During the other months, he is in his office at CalVO, studying the samples he’s collected. “I spend a lot of time looking at microscope slides of rock samples to understand their microscopic structure,” Clynne explained. “I prepare samples for chemical analysis and dating by colleagues or paid contractors.”

He also draws geologic maps from his field maps and notes. “I spend considerable time studying the analytical data, for example rock analyses, with a goal of interpreting the origin and evolution of the rocks — that really means figuring out how volcanoes work,” he said.

He also writes reports and papers of his interpretations for publication by the USGS and in other scientific journals. His work includes attending scientific meetings and symposia on volcanoes; and he spends time reading scientific literature from others on volcanoes and volcanic rocks.

Clynne also reviews his colleagues’ reports, works with others in universities and supervises graduate students on their thesis research in the field.

“One additional aspect of my job is transfer of information to the public. We take people on field trips, teach teachers about volcanoes, do interviews with all types of journalists and media, help National Park rangers tell park visitors about the parks and write nature trail guides,” he added.

 

What’s Lassen like?

When asked if Lassen Volcanic Center erupted would it be like Hawaii’s Kilauea Volcano and Guatemala’s Fuego’s eruption, he said it wouldn’t be like either. The Lassen area is a different kind of volcanic area.

Kilauea is a shield volcano, according to the experts. It is built entirely or most from fluid lava vents. Viewed from the air, shield volcanoes almost resemble a warrior’s shield.

A cinder cone volcano doesn’t have horizontal layers and has a steep conical hill of tephra, also known as volcanic debris, that accumulates around and downwind of a vent. Lassen Volcanic Center has its Cinder Cone remains.

Clynne explained that Cider Cone is a monogenetic volcano, which means it typically has only one period of activity. Subsequent activity could occur nearby and would create a new volcano.

“The same can be said for Chaos Crags — although it is a very different type of volcano than Cinder Cone,” Clynne explained. Chaos Crags is a lava dome complex with a complex history, but with probably only one eruptive period. Within this are six domes, three pyroclastic flows and two hot dome collapses. It also is unlikely to erupt again, but the Lassen Volcanic Center is still active.

Clynne believes that future eruptions are likely to come in the vicinity of Lassen Peak and Chaos Crags.

What is now called Brokeoff Mountain began as Mount Tehama — a volcano for about 200,000 years. It consisted of pyroclastics, made up of very hot ash, lava fragments and gases, and andesitic lava flows. The latter refers to the fine-grained, igneous rocks that are common to the area. Brokeoff Mountain last erupted about 350 years ago.

Other volcanic vents began to appear in the area with a final, large lava flow to the northeastern flank. This left glassy dacite on the flanks of Mount Tehama.

During following glacial periods, combined with extensive hydrothermal activity, major erosion took place. This led to the collapse of Mount Tehama and the remainder is now Brokeoff Volcano, also known as Brokeoff Mountain.

The remaining caldera that is about 2 miles in diameter filled in with debris and material from later eruptions in the area. Further activity eventually created more than 30 other cones sometimes known as the Lassen Domes.

A composite or strato volcano is a conical shape that consists of layers of solid lava flows mixed with other rock. This kind of volcano is the type that spews ash and lava from the mouth. These are the kind most people think of when they consider a volcano erupting. Mount St. Helens is this type. Guatemala’s Volcano Fuego is an example of a composite volcano.

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2 thoughts on “Lassen Volcanic National Park’s threat a reality, but not in our lifetime

  • July 25, 2018 at 9:27 am
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    Excellent story by a skilled, veteran writer.

  • July 25, 2018 at 10:50 am
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    This was a very interesting story of my favorite mountain. I have been on top three times in my teen years. My bucket list consists of one more trip up in my lifetime.. I am now 80 years old and am trying to convince my kids to go with me. I have told them how easy it is with the switch back trail. I just recently did Diamond Head in Hawaii. It is not nearly as high as Lassen but it has three tiers of stairs and some switch back so it is a harder climb up. hope to make it in the next year or so.

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