Lava production . . . has continued since July. Flows from this vent moved down the S flank of the volcano and destroyed 17 more homes in mid-December. Lava output remained at ~500,000 m³/day. The active lava pond level fluctuated from overflowing to ~12 m below the rim. The shield surrounding the vent has reached about 48 m height.

A lobe that consumed two houses on 7-8 December stagnated on 9 December because of collapses and breakouts within the tube system feeding it (figure 47). On 12 December a flow started down the flank farther to the E (figure 47), reaching the break in slope on the 14th.

On 17 December this flow destroyed another house, then crossed the coast highway the next day at 0918. At 0330 on the 19th the first house in the Kalapana Gardens subdivision was overrun by lava and in the next few hours 15 more homes were destroyed. By 21 December that flow was stagnant, with no lava movement observed in skylights in the lava tubes above 300 m elevation. About 100 homes had been evacuated during the emergency; people were allowed to return to their homes on 22 December. Aerial photographs of the lava that destroyed 11 houses and entered the ocean on 28 November showed that 0.07 km² of new land was added to the island.

During the following week, lava flows were confined to within 1-2 km of the vent, mostly to the E and NE. On 31 December, a breakout from a reoccupied tube system at ~495 m elevation fed a new slow-moving flow, which generally remained on top of previous flows but burned some vegetation along its eastern edge. This flow stopped at ~395 m elevation, ~5 km from the coast highway.

Low-level harmonic tremor continued in the eruption zone, with intermittent bursts of tremor beneath Kīlauea's summit originating at depths from 10 to nearly 60 km. Microearthquakes persisted at a moderate rate beneath the summit and the East rift zone. Earthquakes were most numerous beneath the S flank of Kīlauea with foci at depths of 5-10 km. Summit tilt showed no change (figure 45).

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.

Information Contacts: C. Heliker and R. Koyanagi, HVO.