During 16-22 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. Visual observations and thermal anomalies detected in satellite images revealed active surface lava flows.

The vent in Halema'uma'u crater continued to produce a diffuse white plume that drifted mainly SW. Small amounts of ash were retrieved from collection bins placed near the plume. The sulfur dioxide emission rate at the summit remained elevated; 1,300, 1,000, and 400 tonnes per day were measured on 16, 17, and 18 September, respectively. The 2003-2007 average rate was 140 tonnes per day. During 16 and 17 September, two hybrid earthquakes were followed by 20-40 minutes of sustained tremor. The plume turned briefly "dusty" after the first event and incandescent tephra was ejected onto the rim after the second event; both produced glassy spatter.

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)