Volcano Watch: 1967-68 Halemaʻumaʻu eruption was another crater-filler on Kīlauea

Kīlauea’s activity from 2018 until now has been compared to cycles of summit collapse and refilling of lava prior to 1924. But Kīlauea also exhibited similar behavior during the 1967-68 Halema‘uma‘u eruption.

We can learn about how the Hawaiian Volcano Observatory monitored Kīlauea prior to and during the 1967-68 Halema‘uma‘u eruption by reading reports documenting activity at that time.

Observatory staff wrote during the 1960s: “The current eruption in Halema‘uma‘u is especially interesting because events seem to be following the same general pattern that was recorded again and again during the pre-1924 Kīlauean activity.”

In March and December 1965, middle East Rift Zone eruptions occurred that partially drained the magma storage system at Kīlauea summit and caused modest subsidence. The 2018 lower East Rift Zone eruption of Kīlauea drained the summit magma chamber on a larger scale, resulting in caldera collapse.

Similar timeframes of quiet, non-eruptive periods ensued at the summit of Kīlauea following the 1965 and 2018 eruptions. About two years after each eruption, the summit magma reservoir recharged and eruptions occurred.

Hawaiian Volcano Observatory staff wrote that the 1967-68 eruption was preceded by only about “one hour of gradually increasing harmonic tremor…though the eruption has been ‘expected’ for over a year.” Gradually increasing earthquake rates and inflation over the months prior signaled to staff that an eruption could be coming.

Likewise, modern observatory staff has monitored increasing rates of earthquakes and ground deformation for weeks to months prior to the recent eruptions at the summit of Kīlauea. The immediate harbinger of these eruptions has occurred within a similar timeframe of about an hour, as ascending magma breaks rock and causes seismicity.

In 1967, Hawaiian Volcano Observatory had 12 seismometers and two tiltmeters monitoring Kīlauea’s summit. Though the seismometers were telemetered to the observatory, the tiltmeters were done by hand, being read manually every 2 to 12 hours.

Today, the Kīlauea summit monitoring network includes similar numbers of seismometers (18) and tiltmeters (4), but it has expanded to include other monitoring datasets. For example, GPS stations record three-dimensional ground motion, gas-stations record volcanic gas emissions and other meteorological data; gravimeters track accumulation and loss of magma beneath the surface; a laser rangefinder tracks elevation of the crater floor; and webcams capture imagery (visual and thermal) documenting changes on the surface and eruptive activity.

Compared to the manual data monitoring of 1967, telemetry advancements and digitization allow scientists to observe near real-time monitoring data remotely. Much of these data are available to the public on the observatory website, including the popular livestream camera.

In their 1967 eruption reports, observatory staff observed that “Halema‘uma‘u is in the process of being filled.” The eruption, which began on Nov. 5, 1967, went on for another 251 days and filled about 370 feet of lava in the crater.

Post-2018 eruptions within Halema‘uma‘u, which began in December 2020, September 2021, January 2023 and June 2023, continued for two weeks to over a year, and have filled the crater a total of more than 1,270 feet.

Tom Wright and Fred Klein, in their 2014 publication noted of Hawaiian Volcano Observatory in the 1960-70s: “Along with improved instrumentation and methods came increased challenges to the HVO staff as eruption frequency underwent a dramatic increase.”

Staff today have seen similar improvements in monitoring and research, especially with funding supplied through the Additional Supplemental Appropriations for Disaster Relief Act of 2019. Eruptions over the past several years, which include several at Kīlauea summit and one on Mauna Loa, have certainly kept staff busy, but have also provided unprecedented opportunities for learning and strengthening relationships with our partners and communities on the Island of Hawai‘i.

Similarities can be drawn between Kīlauea’s behavior prior to 1924 and discrete other periods, including the 1967-68 eruption and the 2018 summit collapse and subsequent refilling eruptions. These examples are a good reminder that a volcano’s past behavior can offer clues as to how it might behave in the future.

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