During 23-27 September, HVO reported that lava flowed SE from underneath Kilauea's Thanksgiving Eve Breakout (TEB) and rootless shield complex through a lava tube system, reaching the Waikupanaha ocean entry. Lava was not seen entering the ocean on 28 and 29 September. Visual observations and thermal anomalies detected in satellite images revealed active surface lava flows on most days. On 23 September, weak incandescence was detected from inside Pu'u 'O'o crater and from a gas vent in the E crater wall. Explosive activity at the ocean entry on 26 September was possibly caused by a small bench collapse.

The vent in Halema'uma'u crater continued to produce a diffuse white plume that drifted SW and W. Small amounts of ash were retrieved from collection bins placed near the plume. Weak incandescence from the vent, about 200 m below the Halema'uma'u crater floor, was visible at night. Rushing gas and rockfall sounds were occasionally heard in the vicinity of the vent. Preliminary measurements indicated that the sulfur dioxide emission rate at the summit remained elevated; 400, 700, and 665 tonnes per day were measured on 23, 24, and 28 September, respectively. The 2003-2007 average rate was 140 tonnes per day. On 26 September, a series of rockfalls accompanied an apparent collapse of the vent floor, causing the lava level to drop and the plume to turn "dusty brown" for several minutes. On 28 September, a spattering lava pond was seen inside the vent.

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)