A minor intrusion of magma into the upper E rift zone was recorded on 22 October. At 1840, an earthquake swarm began near Pauahi Crater (6 km downrift from the summit), and summit deflation started 8 minutes later. Seismic activity declined about 2000, and deflation leveled off at about 2200, after 1.9 µrad of movement had been recorded. In the 24 hours before the intrusion, seven earthquakes with magnitudes of 3.1-4.2 had occurred at less than 5 km depth along the middle and lower E rift.

At press time, a second intrusion was recorded. An earthquake swarm began on 2 November at about 1415 and summit deflation started less than 30 minutes later. Between 1,000 and 1,500 earthquakes occurred at depths from 4 km to less than 1 km, migrating from just above Kokoolau Crater (about halfway between the caldera rim and Pauahi Crater) 2-3 km downrift to the Heake Crater area. About 4.5 µrad of deflation took place in the summit area before seismicity ended around 1700, and another 0.5 µrad of deflation were recorded in the succeeding 24 hours. In contrast to the aftermath of the smaller 22 October intrusion, inflation did not resume immediately after deflation ended, tilt remaining essentially stable. During and just after the intrusion, no changes in amount or composition of gas emission were observed at various standard sites.

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: Hawaiian Volcano Observatory, USGS.