HVO reported that on 9 March vigorous spattering as high as 50 m was noted from the W end of the Kamoamoa fissure, which had opened on 5 March, along Kilauea's east rift zone between Napau Crater and Pu'u 'O'o. Low lava fountains fed a channelized 'a'a lava flow, 80-290 m wide, that advanced at least 2.9 km to the SE. The lava flow waned starting at 1700 and spattering from the fissure stopped around 2230. The Volcano Alert Level was lowered to Watch and the Aviation Color Code remained at Orange.

During 9-10 March gas measurements showed a sulfur dioxide emission rate of about 4,400 tonnes/day from all east rift zone sources. The rate dropped to 350 tonnes/day on 10 March, and to 100 tonnes/day on 13 March, a value lower than those measured for the months before the Kamoamoa fissure eruption. Seismic tremor declined, but remained elevated above pre-Kamoamoa eruption levels at the summit and the eruption site. During 13-15 March incandescent areas were visible within Pu'u 'O'o crater.

At the summit caldera, a gas plume from the deep pit within Halema'uma'u crater drifted mainly SW during 9-15 March. The level of the lava in the pit was about 220 m below the crater floor, confirmed during an overflight on 9 March. It could not be observed during an overflight the next day because the bottom of the vent was obscured by rubble. Incandescence was occasionally seen in the web camera. An overflight on 14 March revealed that lava was present in the vent; the level slowly rose during the night. On 15 March tephra and fresh spatter was collected from an area beneath the plume.

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)