A new fissure opened on the S flank of Pu`u `O`o soon after a M 4.3 S-flank earthquake on 2 October at 1951. Vigorous lava production from the fissure started the next morning at about 0300, as tremor amplitude increased to ~4x background level, marking the onset of E-52. . .. The fissure, 65 m long and subparallel to the axis of the East rift zone, developed four spatter cones and fed pahoehoe flows that moved southward (figure 86). Distal ends of the channelized pahoehoe flows turned into aa, advancing ~3 km from the fissure. Most of the lava was extruded from the two vents closest to Pu`u `O`o. Lava production from the E-51 vent system had paused on 27 September, but by 1530 on 3 October a sluggish lava flow was observed ~100 m from the E-51 vent.

Figure 86. Lava produced by the first 10 years of Kīlauea's East rift zone eruption, January 1983-early January 1993, with lava from episodes 1-47, 48, 49, 50-51, and 52 indicated by contrasting patterns. Stars mark sites of active lava flows in early November 1992. Courtesy of HVO.

By the morning of 4 October, only the two easternmost E-52 vents remained active. Lava from these vents formed a single flow that ponded just S of Pu`u `O`o at ~730 m altitude. Vigorous activity had resumed from the E-51 vent, breaking out from a tube ~1 km downslope from the vent and ponding on the shield built by E-51 lava. By evening, the volume of lava emerging from the E-51 vent exceeded the volume being erupted from the E-52 vent.

The ponded area below the E-52 vent was breached on 6 October at 1550. The resulting flow advanced over earlier E-52 aa, and by evening had reached forest to the SE. Pahoehoe and aa lava emerged very sluggishly from the E-52 vent 7-16 October, advancing only a few hundred meters from a single vent. During the same period, E-51 lava flowed from several breakouts on the shield. One of these formed a channelized aa flow that entered a forested area at ~730 m altitude by 8 October, but stagnated downslope by the 12th.

Episode-51 lava continued to flow down the shield to the SE and SW. Most of these pahoehoe flows were fed into a large ponded area at ~720 m elevation. No active flows were evident below that level on 16 October, but sluggish tube-fed pahoehoe flows had reached 640 m altitude SW of the E-51 shield by the 22nd, burning the forest at times. Flows to the SE had ceased.

The flow to the SW moved over a steep scarp (Holei Pali) and reached 60 m elevation by 3 November. Lobes cascaded over a small scarp (Paliuli), ponding at its base, then headed E along the foot of the scarp. Lava crossed the Chain of Craters highway during the evening of 7 November and entered the ocean on the evening of the 8th. The lava formed a small bench on the E edge of Kamoamoa Bay, extending nearly 20 m into the ocean and spreading laterally along the coast.

The lava lake in the bottom of Pu`u `O`o crater had been rising before the onset of E-52, but once lava production began at the surface, pond depth dropped rapidly, and by 12 October, the depth to the lake surface was estimated to exceed 75 m. It remained deep (~70 m) through early November. The drop in lava level revealed two inlets to the lake on the W wall. Lava entered at ~70 m depth and descended into a plunge pool ~15 m below. Very active cycles in the lake that lasted about an hour each began on 18 October and continued through the 21st. Large rockfalls produced dust plumes on 29 and 31 October.

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 P. Okubo, HVO.