HVO reported that during 19-25 September fissure segment D from Kilauea's 21 July fissure eruption continued to feed an advancing 'a'a lava flow that occasionally overflowed its channel edges. Several of the lava flows that branched from the main channel continued to advance, widening and lengthening the flow field. A few small earthquakes were located beneath Halema'uma'u crater, the upper E rift zone, the S flank, and the lower SW rift zone during the reporting period.

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)