During the first part of January, lava reoccupied the tube system extending SE from the shield that has been growing since 20 July. Lava outbreaks from the tube system occurred to 365 m elevation, intermittently producing short tube-fed flows for two weeks. During the last half of the month, a new tube system developed on the W side of the lava field, on the E side of the 1984 aa flow. Many breakouts in the area between 485 and 515 m elevation caused flows only a few hundred meters long. All tube-fed flows were of small volume. Most activity was in the shield vent area, adding bulk to the shield through tube-fed breakouts on the E side, not pond overflows as in previous weeks. Periodic overflows did occur, but the shield remained ~46 m high.

On 1 February, a flow poured into a NE-trending fissure 3.8 km NE of the pond and reappeared in a parallel fissure 800-1,100 m downrift, overflowing an area of ~75 x 10³ m² before stagnating on the night of 3 February. New cracks up to 2 m wide opened for a distance of ~1 km.

Weak harmonic tremor continued near the eruption site. The number of microearthquakes remained at average levels in shallow summit region and East rift zone. Deep crustal earthquakes continued at moderate levels beneath the S flank adjacent to the eruptive area. Summit tilt remained unchanged with minor fluctuations.

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.