During 14-20 September, HVO reported that the level of the lava-lake surface in the deep pit within Kilauea's Halema'uma'u crater periodically fluctuated and circulated. Daily measurements indicated that the gas plume from the vent continued to deposit variable amounts of ash and occasionally fresh spatter nearby.

At the E rift zone, lava in the E lava lake overflowed the E rim of Pu'u 'O'o crater on 13 September and advanced a few hundred meters. Lava erupted within the W lava lake and the next day overflowed the W edge of the crater through two broad gaps in Pu'u 'O'o cone, spreading up to several hundred meters downslope and mantling the W flank of Pu'u 'O'o. The flows had stopped by the evening of 15 September. During 15-16 September the level of the lava lakes had dropped 10-15 m. During 17-18 September the W lake was inactive and the E lake weakly bubbled and slowly circulated. Activity within the W lake increased abruptly on 19 September and, during 19-20 September, lava flowed across the W part of the crater floor. On 20 September lava refilled two perched lava ponds on the W edge of the crater, overflowed the southern-most pond, and produced a channelized lava flow that advanced 800 m down Pu'u 'O'o's W flank.

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)