During 12-18 December HVO reported that on most days the circulating lava lake periodically rose and fell in the deep pit within Kilauea's Halema'uma'u Crater. Occasional measurements indicated that the gas plume from the vent continued to deposit variable amounts of ash, spatter, and Pele's hair onto nearby areas.

At Pu'u 'O'o Crater, glow emanated from spatter cones on the SE part of the crater floor, from a spatter cone at the NW edge of the floor, and from a lava lake on the NE part of the floor which was mostly covered by a spatter cone. The lava lake overflowed during 12-13 December, and on 13 December lava flowed from the SW spatter cone. On 14 December the N rim of the NE spatter cone/lava lake collapsed and was followed by a brief overflow of the lake. A larger lava flow issued from a spatter cone on the N edge of the crater floor, followed by another smaller flow; both flows traveled W, then split and flowed N and S. Another rim collapse from the NE spatter cone/lava lake and small overflow were observed the next day.

Lava flows remained active in two branches on the coastal plain: a small W branch, and a larger E branch with scattered activity extending from the pali to the coast E of the easternmost boundary of Hawai'i Volcanoes National Park. An ocean entry was marked by a weak and variable plume near Kupapa'u, with lava entering the water in at least two different areas. A new lava flow at the top of the pali was observed on 11 December. On 15 December observers noted that lava flows were active in a 1-km-wide area that stretched from near the base of the pali to the coast. On 16 December HVO noted that a lava delta at the ocean entry had slowly grown to be 50 m wide.

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)