During 1-6 October at Kilauea, lava entered the sea at several points along two active lava deltas (Middle Highcastle and Wilipe`a). No surface flows were visible on the deltas; lava either entered the water via lava tubes or inflated the delta underneath the surface. Several surface flows were visible on the coastal flat, while no incandescence was seen on Paliuli and only a few glowing spots were visible on Pulama pali. On the 3rd, the swarm of long-period earthquakes and tremor beneath Kilauea's caldera that was first active beginning in June, picked up strongly, with numerous long-period events persisting for about a day. Elsewhere there was no unusual seismicity. Around the time of increased seismicity, small periods of inflation and deflation occurred at Pu`u `O`o and Uwekahuna. Otherwise, tiltmeters recorded no unusual deformation.

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)