Based on visual observations from HVO and National Park Service (NPS) crews as well as web camera views, HVO reported that during 19-25 March lava flow activity from Kilauea's Thanksgiving Eve Breakout (TEB) shield was mostly concentrated in and near the Royal Gardens subdivision and at multiple points along the Waikupanaha and Ki ocean entries. Lava flows advanced eastward over an old sea cliff and onto the 1990 lava delta, and were 120 m W of the viewing area on 23 March. Flows through a kipuka produced fires during 18-22 March.

During the reporting period, Kilauea summit earthquakes were located beneath the S-half of the caldera, beneath Halema`uma`u Crater, N of Pu'u 'O'o, along the S-flank faults, and along the SW rift zone. At 0258 on 19 March, an explosion from Halema'uma'u Crater scattered debris over an area of about 75 acres (30 hectares), covering a portion of Crater Rim Drive and damaging the overlook. On Crater Rim Drive, the debris was up to 2 cm in diameter and increased in size and thickness towards the overlook. The largest block ejected during the explosion was about 1 cubic meter. Small impact craters from 30-cm-blocks were abundant in the overlook area. The event was the first explosive activity in the crater since 1924. During 19-24 March, seismic tremor levels were elevated above their already high pre-explosion levels and incandescence at the gas vent was intermittent. Small incandescent tephra particles erupted from the vent overnight during 23-24 March and were deposited on the rim of the crater. On 24 March, the gas plume from the vent became ash-laden and rose to an altitude of about 2.8 km (9,200 ft) a.s.l. The plumes drifted SW. Geologists found Pele's hair, Pele's tears, and spatter in the overlook area. The largest spatter was 10 cm in diameter. During 24-25 March, overnight observers reported incandescence at the base of the continuous ash plume. Based on a pilot observation, the Washington VAAC reported that ash plumes rose to an altitude of 2 km (6,500 ft) a.s.l. on 25 March and drifted SW. The eruption was the first to produce lava in Halema'uma'u since 1982.

Sulfur dioxide emission rates from the summit area have been elevated at 2-4 times background values since early January. The emission rate fluctuated between 1,200-2,200 tonnes per day during 18-23 March, compared to a background rate of 150-200 tonnes per day. On 23 March, the emission rate was 2,200 tonnes per day at Pu'u 'O'o. Sulfur dioxide concentrations were mostly below detection limits at the Jaggar museum and the Kilauea Visitors Center.

Geological Summary. Kilauea overlaps the E flank of the massive Mauna Loa shield volcano in the island of Hawaii. Eruptions are prominent in Polynesian legends; written documentation since 1820 records frequent summit and flank lava flow eruptions interspersed with periods of long-term lava lake activity at Halemaumau crater in the summit caldera until 1924. The 3 x 5 km caldera was formed in several stages about 1,500 years ago and during the 18th century; eruptions have also originated from the lengthy East and Southwest rift zones, which extend to the ocean in both directions. About 90% of the surface of the basaltic shield volcano is formed of lava flows less than about 1,100 years old; 70% of the surface is younger than 600 years. The long-term eruption from the East rift zone between 1983 and 2018 produced lava flows covering more than 100 km2, destroyed hundreds of houses, and added new coastline.

Sources: US Geological Survey Hawaiian Volcano Observatory (HVO), Washington Volcanic Ash Advisory Center (VAAC)