Most February activity occurred along a tube system SE of the vent that has fed a lava pond and built a small shield . . . since July. The elevation of the pond was ~656 m asl. There was no further flow activity into the NE-trending fissure after 3 February (figure 47). Beginning at ~520 m elevation the first part of the month, breakouts along the tube system gradually migrated downslope. By mid-month, most activity was within a 60 m elevationn range near the 335 m contour, 6 km SE of the lava pond. From the 15th on, there were two concurrent flows, one traveling along the E margin of the 1984 aa flow and the second on top of the 1984 aa, both emanating from the same tube system at ~450 m elevation. The first flow was intermittently active. A new surge of lava advanced on 25-27 February, then stagnated on the 28th at 130 m elevation, < 3 km from the coast.

The 2nd flow had reached 260 m elevation by the 22nd, then ran off the W side of the 1984 aa and traveled down to 130 m through forest and grassland, stagnating on the 24th. Both flows were narrow, low-volume, channeled aa, too small to show on the scale of figure 47. Lava did not directly threaten residents of nearby Royal Gardens subdivision, but started smoky brush fires 23-26 February. Residents along the E edge of the subdivision were evacuated for one day and the County Fire Dept set backfires to protect the homes in the area.

Since 28 February, activity has been limited to pond overflows on the shield, indicating blockage within the tube system. The height of the shield remained ~46 m above the pre-1983 surface and the daily output of lava was estimated to be 500,000 m³/day. There has been no significant change in summit tilt.

Harmonic tremor persisted at low levels . . . near the vent area. The number of microearthquakes remained at a relatively low level in the summit and East rift zone. Earthquake activity was centered mainly along the S flank of Kīlauea and the vicinity of the Kaoiki fault (between Kīlauea and Mauna Loa). A burst of deep seismicity 60 km N of Keahole Point on the W side of the island started with a M 4.8 event at 1622 on 3 February, followed by 24 aftershocks ranging from M 2.5 to 4.0 over the next three weeks.

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.