Volcano Watch: Explosive Eruptions from Halemaʻumaʻu in 1924
May 2023 marks the 99th anniversary of a sequence of explosive eruptions from Kilauea’s summit that occurred over 16 days from May 11–27, 1924. During this eruption, about 60 explosions occurred from Halema’uma’u with fragments ranging from volcanic ash to large blocks the size of cars falling around the summit caldera.
For nearly two decades prior to the explosive eruptions in 1924, Halema’uma’u hosted a large lava lake. In February 1924, this lava lake drained over the course of two days, leaving behind an incandescent crater that was around 380 ft deep by 1,700 ft wide (115 m deep by 520 m wide). Halema’uma’u remained an empty crater for the next two months.
April 1924 saw the summit of Kilauea hit with an earthquake swarm that migrated down the East Rift Zone. Residents of Kapoho in the lower East Rift Zone felt more than 200 earthquakes on April 22–23, which resulted in an approximately 4-mile-long by 1-mile-wide (6.5 by 1.6 km) tract of land cracking and subsiding. This included the area near the eastern point of the Island of Hawaii dropping by about 14 ft (4 m) and the ocean covering nearly a half mile (1 km) of previously dry land. Despite the shaking and subsidence in the lower East Rift Zone, associated with lava draining from the summit lava lake, no eruption occurred from the rift zone.
On April 29, 1924, the floor of Halema’uma’u started to subside and eventually reached around 600 ft (180 m) below the crater rim by the time the first explosions occurred from Halema’uma’u during the nighttime hours of May 10–11. Hot rocks from this explosion were noticed near the rim of Halema’uma’u on the morning of May 11 by a national park ranger. This prompted road closures within Hawaii National Park (as it was named then), as well as a close call when the park superintendent and two observers were pelted by ash during another explosion that sent ash up to 3,000 ft (nearly 1 km) high. In fact, a 100-pound (45 kg) boulder had been thrown over the group’s vehicle nearby, prompting the roadblock to be pushed back even farther.
Explosions of ash, lapilli, and blocks continued to be ejected from the crater. The largest of these explosions occurred on May 18 with lightning-charged ash going up higher than 4 miles (6.5 km), as well as spreading across the crater floor. Several people were near the crater rim when this explosion occurred. Unfortunately, a resident of Pahala was hit by a block and died that night at the hospital in Hilo. This was the only fatality during these explosive eruptions.
Explosions continued, although smaller than the one on May 18, and by May 27, when the explosions ended, Halema’uma’u was about twice as wide and eight times as deep than before. Blocks weighing as much as eight tons (8,000 kg, equivalent to 10 cows) had been hurled as far as 1,600 ft (500 m) from the crater.
Scientists originally proposed that the lava lake’s drainage exposed cracks in the crater floor that allowed groundwater to enter the system. This groundwater may have flashed to steam and resulted in the many explosions over the 16 days in May 1924. However, new research being undertaken by the Hawaiian Volcano Observatory could reveal other explanations for these explosive events. This research will help us to better understand these explosive bursts that occurred nearly a century ago and compare them with the more recent explosions from the summit of Kilauea in 2018.
Volcano Activity Updates
Kilauea is not erupting. Its USGS Volcano Alert level is ADVISORY.
Webcams show no signs of active lava in Halema’uma’u crater, at the summit of Kilauea in Hawaii Volcanoes National Park. Over the past week, summit tiltmeters showed inflation and seismicity has been variable. The summit sulfur dioxide (SO2) emission rate was most recently measured on May 3, when it totaled 135 tonnes per day.
Mauna Loa is not erupting. Its USGS Volcano Alert Level is at NORMAL.
Webcams show no signs of activity on Mauna Loa. Seismicity remains low. Summit ground deformation rates show inflation above background levels, but this is not uncommon following eruptions. SO2 emission rates are at background levels.
There were five earthquakes above magnitude 3 and with 3 or more felt reports in the Hawaiian Islands during the past week: a M3.5 earthquake 9 km (6 mi) ESE of Pahala at 32 km (19 mi) depth on May 10 at 4:56 a.m. HST, a M3.8 earthquake 11 km (6 mi) ENE of Pahala at 32 km (19 mi) depth on May 7 at 11:58 p.m. HST, a M3.3 earthquake 0 km (0 mi) NE of Pahala at 39 km (24 mi) depth on May 7 at 7:35 a.m. HST, a M3.0 earthquake 35 km (21 mi) ENE of Waimanalo Beach at 8 km (5 mi) depth on May 5 at 4:26 p.m. HST, and a M3.7 earthquake 12 km (7 mi) SSE of Fern Forest at 5 km (3 mi) depth on May 4 at 1:05 p.m. HST.
HVO continues to closely monitor Kilauea and Mauna Loa.
Please visit HVO’s website for past Volcano Watch articles, Kilauea and Mauna Loa updates, volcano photos, maps, recent earthquake information, and more. Email questions to askHVO@usgs.gov.
Volcano Watch is a weekly article and activity update written by U.S. Geological Survey Hawaiian Volcano Observatory scientists and affiliates.