In April . . . lava traveled through tubes and plunged into the ocean. Lava also occasionally escaped from the tubes and formed surface flows. In mid-April, flows escaped lava tubes at three locations: a) along the E side of the Kamoamoa lava delta, b) at 61 m elevation, and c) at 610 m elevation. The latter site fed aa flows that descended to 488 m elevation.

A 2-day pause . . . on 15-16 April [resulted] in stagnant surface flows. During this time the volume of lava entering the ocean backed off to a residual trickle.

For the interval 29 March to 11 April the surface of the active lava pond rose from 90 m to 84 m below the crater rim. Following the 2-day pause, the surface of the active lava pond at the bottom of Pu`u `O`o crater stood at 79 m below the crater rim.

During 1-17 April, tremor . . . often sustained amplitudes 2-3x larger than background. Beginning 18 April, tremor amplitude began to drop to near-background levels, marking the start of irregular banding patterns on the seismic record. The patterns consisted of low-level tremor alternating with 1-2 hour bursts of higher amplitude tremor.

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: T. Mattox and P. Okubo, HVO.