The Hawaiian Volcano Observatory (HVO) reported that the eruption within Kilauea’s Kaluapele summit caldera, characterized by episodic fountaining, incandescence, and intermittent spatter from craters along the SW margin of Halema’uma’u Crater, continued at variable levels during 2-9 December. During a helicopter overflight on 2 December volcanologists observed a spattering lava surface deep within the N vent. Incandescence at both the N and S vents was visible overnight during 2-5 December, and was accompanied by flames from burning gas (likely hydrogen gas) and occasional weak spattering. Persistent low-to-moderate tremor was punctuated by minor seismic tremor bursts suggestive of irregular gas pistoning at depth. Periods of gas pistoning became more frequent overnight during 4-5 December and incandescence at the N vent intensified. Spattering at the N vent increased by 0330 on 5 December. Large flames arose from the S vent and from a crack adjacent to the N vent.

During the episode of lava fountaining that ended on 25 November a new vent opened within the N vent; the original vent (the right vent) and a new vent to the left, separated by a septum of rock. Lava erupted from the N vent at 1250 on 5 December and lasted for about two minutes. Three more lava overflows, each lasting 10-20 minutes, occurred later that day during 1700-2000. A short lava overflow was recorded at 0235 on 6 December and was followed by continuous overflows at 0337. Most of the overflows came from the left vent, but by around 0700 the right vent also began overflowing, increasing the effusion rate and producing fountains. Lava fountains rose 5-20 m and produced ribbon-like flows onto the Halema’uma’u Crater floor. The S vent continued to glow and spatter intermittently but produced no overflows. Activity escalated and by 0845 sustained lava fountains at both the right and left vents of the N vent were 15-30 m high. Lava fountains rose from the S vent at 0849 and quickly reached 370 m high while the fountains at the N vent dropped to 150 m. All three vents were producing lava fountains, which was an extremely rare event. By 0940 the S vent fountains were about twice as high as the N vent fountains. The S vent became enlarged and produced fountains over 300 m tall that arced towards the S wall of the crater. Molten spatter and pumice from the S vent destroyed the “V3” streaming camera site, located within the closed area, just before 1000.

The eruption was sustained for about 12 hours with lava fountains rising as high as 370 m. The dual fountains at the N vent ceased at 1150 and the S vent ceased erupting at 2052. The fountains produced an estimated 12 million cubic meters of lava that covered 50-60% of the crater floor. The combined average eruption rate was an estimated 190 cubic meters per second with a peak of 1,000 cubic meters per second just before 1000 when fountains at the S vent rose to high levels. The associated eruption plume, composed of water vapor, sulfur dioxide gas, Pele's hair, reticulite and fine ash, rose 6.1 km (about 20,000 ft) above ground level. Tephra including Pele's hair and fine ash carried in lower levels of the plume fell in Pahala and other communities SW of the vents. Satellite imagery showed that the upper regions of the gas-and-ash cloud drifted E across lower Puna and reached an area well out to sea before turning S. Reticulite pieces up to about 75 mm fell along Chain of Craters Road E of the summit.

Both vents and the crack adjacent to the N vent were intermittently incandescent overnight during 6-9 December. Incandescent lava on the crater floor gradually cooled and went dark during 6-7 December, though spatter-fed flows on the slopes S of both vents remained partially incandescent and moved downslope through 9 December. The Volcano Alert Level remained at Watch (the third level on a four-level scale) and the Aviation Color Code remained at Orange (the third color on a four-color scale).

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)