Report on Kilauea (United States) — 18 August-24 August 2021
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
18 August-24 August 2021
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2021. Report on Kilauea (United States). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 18 August-24 August 2021. 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 swarm of earthquakes beneath the S part of Kilauea that began at 1630 on 23 August continued into the early morning of 24 August. The earthquake swarm increased in intensity at 0130 and was accompanied by an increase in the rate of ground deformation to the W of the swarm, as recorded by the Sandhill tiltmeter. This possibly indicated that there was magma movement 1-2 km beneath the S part of the caldera. Over 140 earthquakes were recorded during 24 August, the largest of which was an Mw 3.3; a majority of them were less than Mw 1. Small earthquakes continued at a rate of at least 10 earthquakes per hour through 24 August. As a result, the Aviation Color Code and the Volcano Alert Level were raised to Orange and Watch, respectively.
Geological Summary. 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.