The Hawaiian Volcano Observatory (HVO) reported that an eruption began at Kilauea’s Kaluapele summit caldera on 23 December. At approximately 0200 on 23 December elevated seismicity accompanied by rapid summit inflationary ground motion (UWH and SDH tiltmeters) was recorded in the summit region. By 0220 webcams showed that eruptive activity had begun near the SW wall of Halema’uma’u crater. At 0241 the Alert Level was raised from Advisory to Warning and the Aviation Color Code was raised from Yellow to Red. At 0245 the summit region tiltmeters switched to deflation. A line of fissures erupted lava fountains that fed flows across the Halema’uma’u crater floor, and the down dropped block within the summit caldera. Between 0230 and 0430 vents also opened briefly to the NE along the crater floor. At 0430 the lava fountains were observed rising to heights up to ~80 m (260 feet). Molten material, including lava bombs, were ejected from the floor up onto the W caldera rim. By 0500 lava covered an estimated 1.6 square kilometers (400 acres) of the caldera floor. A plume of gas and fine particles rose 600-1,200 m (2,000-4,000 feet), reaching 1.8-2.4 km (6,000-8,000 feet) above sea level, and drifted SW.

By 0630 the eruption had stabilized within the crater and there were no threats to infrastructure, so HVO lowered the Alert Level to Watch and the Aviation Color Code to Orange at 0643. The initial vent along the SW wall remained active. The maximum fountain height was ~90 m (300 feet). Lava flows covered more than 2 square kilometers (500 acres), and the gas emissions persisted. Spatter from the fountains and tephra/Pele’s hair prevented crews from obtaining SO2 emission rates by ground or helicopter.

The eruption continued throughout the day before slowing significantly between 1500 and 1600 and came to an apparent pause. New lava covered approximately 2.6 square kilometers (650 acres), including all of Halema’uma’u and most of the adjacent down dropped block, this area is about 25% of the Kaluapele summit caldera. Based on an estimated lava flow thickness of 1 m, an average effusion rate of 85 cubic meters per second was calculated for the first 8 hours of the eruption. The fountain heights decreased to ~50 m by 1300. Weather conditions prevented measurement of SO2 gas emission rates by normal methods, but nearby stations estimated over 100,000 tons per day (t/d) around 0800 and decreased by half in the afternoon.

Around 1500 summit deflation stopped and the seismic tremor began to decrease. By 1530 the fountains were barely visible and had stopped by 1600. The gas emissions also decreased significantly. Soon after fountaining stopped, lava began to drain back into the original vents, a process that continued through the night. At about 0800 on 24 December low-level eruptive activity began again and around 1100 the lava fountains began to intensify.

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)