HVO reported that the circulating lava lake in the pit within Kilauea's Halema'uma'u Crater started to drop on 9 May and as of 15 May was about 50 m lower than the raised vent rim. The lake-level drop was accompanied by a change from inflation of the summit area to deflation centered near Halema'uma'u Crater. In addition, on 13 May, the focus of deformation changed to the S part of Kilauea's summit caldera and upper Southwest Rift Zone (SWRZ), where rapid and localized inflationary tilt was recorded. Seismicity shifted from Kilauea's summit and the upper East Rift Zone (ERZ) to the S part of the summit; seismicity at the upper SWRZ continued. The number of earthquakes increased on 15 May. The data suggest that magma had moved into a shallow area beneath the S part of the caldera and upper SWRZ. During 16-18 May rates of tilting slowed, and seismicity at the summit and SWRZ remained above background levels but had decreased. By 19 May seismicity rates at the summit were normal and tilit had decreased slightly. The lava lake remained about 45-50 m below the crater floor.

Nighttime incandescence suggested an active lava pond in an isolated vent W of Pu'u 'O'o Crater. The June 27th NE-trending lava flow continued to have active surface flows within 8 km NE of Pu'u 'O'o.

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.

Source: US Geological Survey Hawaiian Volcano Observatory (HVO)