Report on Kilauea (United States) — 2 May-8 May 2018
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 2 May-8 May 2018
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2018. Report on Kilauea (United States). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 2 May-8 May 2018. Smithsonian Institution and US Geological Survey.
19.421°N, 155.287°W; summit elev. 1222 m
All times are local (unless otherwise noted)
On 2 May HVO noted that the intrusion of magma into Kilauea’s lower East Rift Zone (ERZ) continued, with deformation and frequent earthquakes (many felt by residents). Small cracks formed on some of the roads in and adjacent to Leilani Estates. Seismicity at Pu'u 'O'o Crater remained elevated after floor collapses which began on 30 April. Short-lived ash plumes periodically rose from the crater. The lava flows on the pali near the Royal Gardens subdivision were sluggish. Deflation at the summit accelerated around midday, accompanied by a drop in the level of the lava lake.
On 3 May the intensity of the ERZ seismicity decreased slightly, and the eastward migration of hypocenters slowed or ceased; deformation continued. The lava level in Overlook crater dropped over 30 m, though spattering in the lake continued. At 1030 ground shaking from a M 5 earthquake S of Pu'u 'O'o caused rockfalls and possibly a collapse in the crater; an ash plume rose from the crater and drifted SW. More ground cracks in the E part of Leilani Estates formed that afternoon; hot white and blue fumes rose from the cracks. Lava spatter and gas bursts began erupting from 150-m-long fissures just after 1700 and ended around 1830. Lava flows spread less than 10 m, and strong sulfur dioxide odors were noted. The lava lake in the Overlook Crater dropped an additional 37 m.
By the morning of 4 May three fissures were active; fissure 2 opened at 0100 and fissure 3 opened around 0600. Spatter was ejected as high as 30 m and lava flows were traveling short distances. Large, loud bubble bursts occurred at fissure 3. Ash plumes from intermittent collapses at Pu'u 'O'o continued to rise above the crater, and the 61 G lava flow was no longer being fed. A M 6.9 earthquake occurred at 1233, centered on the S flank. Fissures 4 and 5 opened at 1039 and 1200, respectively, and by 1600 there were six, each several hundred meters long. The sixth fissure was on the E edge of the subdivision. The Hawaii Emergency Management Agency stated that multiple agencies were assisting with the mandatory evacuation of residents (about 1,700) in the Leilani Estates and Lanipuna Gardens subdivisions. A temporary flight restriction was declared for most of lower Puna. The report noted dangerously high concentrations of sulfur dioxide.
Based on satellite InSAR data, the summit caldera floor subsided about 10 cm during 23 April-5 May. Corresponding to this deflationary trend, the summit lava lake in Overlook crater had dropped to about 128 m below the crater rim since 30 April. Summit seismicity increased during 4-5 May coincident with the M 6.9 earthquake; about 152 events (M 2-3) were recorded. Rockfalls from the inner crater walls produced ash plumes that rose above the Halema'uma'u crater rim on 5 May. New ground cracks on Highway 130 opened on 5 May, and at dawn fissure 7 formed. By mid-afternoon fissure 7 stopped erupting, and the 8th fissure opened at 2044 near fissures 2 and 7. Lava fountains from fissure 8 rose as high as 70 m, and in other areas were as high as 100 m. A lava flow from fissure 7 traveled 260 m NE. The lava lake in Overlook Crater continued to drop.
The eruption from one or two fissures was continuous during 5-7 May, and ‘a’a lava flows from fissure 8 advanced 0.9 km NNE by 1000 on 6 May. HVO warned that poor air quality from sulfur dioxide gas emissions, and smoke plumes from burning asphalt and houses was a health concern. Strong gas emissions rose from the fissures during 6-7 May, though lava effusion was minimal overnight. New cracks crossed Highway 130 west of the eruption site, and some others widened. The level of the summit lava lake continued to drop, and by 7 May was 220 m below the crater rim. Two new fissures emerged on 7 May. The first (fissure 11) opened at about 0930 in a forested area SW of Leilani Estates, and was active for about three hours. The second (fissure 12) opened at about 1220 between fissures 10 and 11. By 1515 both new fissures were active, and the W end of fissure 10 was robustly steaming. According to a news article, lava had covered an area about 36,000 square meters.
Lava effusion at night during 7-8 May was minimal, and by around 0700 on 8 May the ERZ eruption had paused. The fissure system was about 4 km long and continued to strongly emit gas. Ash plumes generated by falling rocks in Overlook crater continued to produced ash plumes. On 8 May the Office of the Mayor stated that 35 structures had been destroyed, and lava covered. HVO maps show the locations and numbers of the fissures.
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.