Hawai'i Volcano Blog

Exploring USGS Volcano Observatories—Part 3: California

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Mount Shasta, a steep-sided Cascade Range stratovolcano in Northern California, looms above Little Glass Mountain, a thick obsidian flow erupted from the Medicine Lake shield volcano about 1,000 years ago. These are just two of the 19 young volcanic areas monitored by the USGS California Volcano Observatory (CalVO). INSET: USGS-CalVO staff, shown here in the observatory’s operations center in Menlo Park, CA, oversee research and monitoring on volcanoes in California and Nevada. Margaret Mangan (far right), who worked at the USGS Hawaiian Volcano Observatory in 1990-1998, is now CalVO’s Scientist-in-Charge. USGS photos.

As part of Volcano Awareness Month, our January Volcano Watch articles are exploring the U.S. Geological Survey’s volcano observatories and their connections to Hawai‘i.

(A complete Volcano Awareness Month program schedule, including descriptions of the talks, is posted on HVO’s website.)

This week: California, here we come!

The USGS California Volcano Observatory (CalVO), with its staff and data center based in Menlo Park, California, is relatively young. But it grew from strong parentage through what was known as the Long Valley Observatory.

Long Valley Caldera in eastern California formed as the result of a huge eruption 760,000 years ago. That event was followed by many smaller eruptions ever since. The caldera is at the southern edge of the Mono-Inyo Craters chain of lava flows and domes, which were active as recently as 300 years ago.


In 1980, seismic unrest in Long Valley Caldera near the resort town of Mammoth Lakes motivated the USGS to begin intensive study and monitoring of the region. This led to the establishment of the Long Valley Observatory (LVO) in 1982.

LVO leaned heavily on techniques that were pioneered at the USGS Hawaiian Volcano Observatory (HVO), including laser ranging, which was further refined in Long Valley to produce an extensive and high-resolution time series of how the caldera inflated and deflated. In fact, Dave Hill, the LVO Scientist-in-Charge from 1982 until 2009, was on staff at HVO in 1964 to 1966!

Although the caldera was the focus of LVO’s monitoring efforts, most LVO staff worked from offices in Menlo Park. They made site visits to the caldera as needed to conduct research and to work with local residents and emergency managers to help them understand the volcanic activity and its potential hazards.

However, Long Valley Caldera is just one of 19 young volcanic areas in California. Recognizing the value of a local authority responsive to state emergency managers and residents, LVO was reorganized and renamed the USGS California Volcano Observatory (CalVO) in 2012. CalVO is now responsible for researching and tracking volcanic activity throughout California and neighboring Nevada (https://volcanoes.usgs.gov/observatories/calvo/calvo_about.html).

Having a formal USGS volcano observatory focused on California has many benefits. These range from better coordination with emergency managers during a crisis, to increased potential for improving awareness of and preparedness for volcanic hazards within local communities.


CalVO has spent its first years of existence supporting a flurry of new research into California’s volcanoes. Among the more significant results has been the discovery that the Salton Buttes, a volcanic area in southern California, are much younger than previously thought—the most recent eruption was only 2,000 years ago!

USGS-CalVO scientists have continued their work in the Long Valley region, where they have documented hazardous gas emissions from Mammoth Mountain, seismic swarms associated with magmatic intrusions, and the general swelling of the caldera due to subsurface magma accumulation.

As the youngest USGS volcano observatory, CalVO has drawn much from the experience of HVO. As was the case for LVO, the current CalVO Scientist-in-Charge, Margaret Mangan, is an HVO alumnus. Many other CalVO staff have also been based in Hawaiʻi at some point in their careers or have conducted research on Hawaiian volcanoes.

CalVO continues to grow. There are big plans to enhance monitoring and research at numerous California volcanoes in the coming years, including the volcanoes in the state’s northern mountains—Lassen Peak, Mount Shasta, and Medicine Lake.

Next week, our USGS volcano observatory series will conclude with a visit to the largest volcanic system in the United States—Yellowstone!


Meanwhile, Volcano Awareness Month in Hawaiʻi continues with upcoming public programs on the east and west sides of the island. Tracking lava flows and lava lakes is the focus of a Hawaiʻi Volcanoes National Park talk on January 24. The current status of Mauna Loa, Hualālai, and Kīlauea volcanoes will be addressed in a presentation at Konawaena Elementary School in Kelealakekua (South Kona) on January 25. Details are posted on the HVO website . Hope to see you there!

Volcano Activity Updates

Kīlauea continues to erupt at its summit and East Rift Zone. This past week, the summit lava lake level varied between about 98 to 172 feet below the vent rim. The 61g flow was still active, with lava entering the ocean near Kamokuna and surface breakouts near Pu‘u ‘Ō‘ō. As of Jan. 15, a secondary branch of the flow was about 1.5 miles from the vent.

The 61g flows do not pose an immediate threat to nearby communities.

Mauna Loa is not erupting. During the past week, small-magnitude earthquakes continued, primarily beneath the upper Southwest Rift Zone at depths less than 3 miles. A small number of earthquakes also occurred on the west flank of the volcano at depths above 8 miles. GPS measurements continue to show deformation related to inflation of a magma reservoir beneath the summit and upper Southwest Rift Zone.

No earthquakes were reported felt on the Island of Hawaiʻi this past week.

Volcano Watch is a weekly article and activity update written by U.S. Geological Survey Hawaiian Volcano Observatory scientists and affiliates.

Call for summary updates at (808) 967-8862 (Kīlauea) or (808) 967-8866 (Mauna Loa); email questions to [email protected].

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