Report on Kilauea (United States) — 16 December-22 December 2020
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 16 December-22 December 2020
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2020. Report on Kilauea (United States). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 16 December-22 December 2020. Smithsonian Institution and US Geological Survey.
19.421°N, 155.287°W; summit elev. 1222 m
All times are local (unless otherwise noted)
HVO reported that a new eruption at Kilauea began on 20 December, after almost a month of pre-eruptive activity that included a dike intrusion. An earthquake swarm on 30 November centered in the middle of the caldera was recorded followed by periods of increased seismicity in the upper East Rift Zone. Spikes in seismicity began on 2 December; at 1745 earthquakes intensified beneath the S part of the caldera; tiltmeters simultaneously recorded accelerated deformation, resulting in about 8 cm of caldera floor uplift. The data suggested that a small intrusion had a volume equivalent to the amount of lava erupted in just 1-2 hours from Fissure 8 during the 2018 eruption. On 3 December seismcity and deformation decreased to pre-intrusion levels.
On 17 December the number and duration of long-period seismic signals increased. An earthquake swarm and deformation were detected during the evening of 20 December. At about 2136 on 20 December an orange glow was evident in IR monitoring cameras, heralding a new eruption, and prompting HVO to raise the Volcano Alert Level to Warning and the Aviation Color Code to Red. Three fissures successively opened on the inner N, NW, and W walls of Halema`uma`u Crater; lava flows quickly boiled away the water lake, creating a vigorous steam plume, before the lava ponded at the bottom. Minor lava fountaining (25 m high) from the fissures was visible, with the tallest fountains reaching 50 m at the N fissure. Occasional blasts originated from the ponded lava. A M 4.4 earthquake beneath the S flank was recorded at 2236.
A gas plume was seen rising from Halema`uma`u Crater and drifting SW at 0215 on 21 December. Later that morning HVO lowered the Volcano Alert Level to Watch and the Aviation Color Code to Orange. The accumulating lava in the crater rose at a rate of several meters per hour. Sulfur dioxide plumes drifted NW. By the morning of 22 December, the surface of the lava lake was about 134 m above the bottom of the crater, or 487 m below the crater rim, and rising 1 m/hour. An estimated 10 million cubic meters of lava had been erupted so far. Sulfur dioxide emission rates remained high, at around 30,000 tonnes/day. Lava effusion stopped at the NW vent during 0730-0800, and, along with the W vent, was inundated by the lava lake sometime before noon.
Geologic Background. Kilauea, which overlaps the E flank of the massive Mauna Loa shield volcano, has been Hawaii's most active volcano during historical time. Eruptions are prominent in Polynesian legends; written documentation extending back to only 1820 records frequent summit and flank lava flow eruptions that were interspersed with periods of long-term lava lake activity that lasted until 1924 at Halemaumau crater, within the summit caldera. The 3 x 5 km caldera was formed in several stages about 1500 years ago and during the 18th century; eruptions have also originated from the lengthy East and SW rift zones, which extend to the sea on both sides of the volcano. About 90% of the surface of the basaltic shield volcano is formed of lava flows less than about 1100 years old; 70% of the volcano's surface is younger than 600 years. A long-term eruption from the East rift zone that began in 1983 has produced lava flows covering more than 100 km2, destroying nearly 200 houses and adding new coastline to the island.