Volcano Watch — The 1955 eruption: the first in lower Puna since 1840

Tomorrow, February 28, marks the 45th anniversary of the start of the 1955 eruption on Kīlauea's lower east rift zone. This was the first eruption of Kīlauea in an inhabited area (lower Puna) since 1840, and the first on the east rift zone since a small eruption near Makaopuhi Crater in 1923.

Kīlauea had been essentially hibernating since the collapse of Halema`uma`u in 1924. Only seven tiny outbreaks occurred in Halema`uma`u over the next ten years, and then total quiet reigned until 1952. A 136-day eruption in Halema`uma`u in summer 1952, and a three-day eruption there and on the adjacent caldera floor in May-June 1954, showed that Kīlauea was awakening, and the 1955 eruption was the clincher. Since then, Kīlauea has erupted in 36 of the 45 years, continuously in the last 18.

The 1955 eruption was preceded by increasing seismicity in lower Puna, as recorded by the one seismometer in the area, in Pahoa. From two earthquakes per day in November 1954, the daily number increased to 15 between February 1 and 23. Thereafter many earthquakes were felt at Nanawale Ranch, and the daily number of instrumentally recorded earthquakes jumped to 600 on February 26 and 700 on the 27th. Some of the felt earthquakes had sounds like explosions, and others shook as if a big truck was passing by.

The eruption began at about 8 a.m., when field workers of Ola`a Sugar Company and residents of `Opihikao village saw fume just southwest of Pu`u Honua`ula. Over the next three days, fissures opened successively downrift from Honua`ula, past Pu`u Ki`i, to just east of Halekamahina, a distance of 4.5 km (2.8 miles). The vents near Pu`u Ki`i erupted a large lava flow that nearly reached the coastline south of Kapoho Beachlots before stagnating on March 7. This flow cut both the Pahoa-Kapoho road and the coastal road south of Kapoho Crater. The Pahoa-Pohoiki road was cut in one place by a flow from the first vent.

On March 3, a new crack opened at the west edge of Kapoho village and quickly extended through the center of town. Lava erupted from it just west of Kapoho but not in the village itself. The crack was along the Kapoho fault, which played an important role in the eruption five years later that destroyed the town.

By March 7 the eruption had stopped, but HVO scientists noted a new swarm of earthquakes, increasing in intensity, coming from the east rift zone on either side of the Pahoa-Kalapana road, 7 km (4 miles) uprift from Honua`ula. Police patrolled the roads, and the National Guard made regular aerial reconnaissance. Residents of Kama`ili were evacuated because of the danger of lava speeding rapidly down the steep slope farther northwest. Kalapana and `Opihikao were also evacuated, because all escape routes to Pahoa were already cut off (roads to Pohoiki) or threatened (road to Kalapana).

Police reported cracks opening on the Pahoa-Kalapana road on the morning of March 12, and lava began to erupt late that afternoon just southeast of Pu`u Kali`u. From then until March 19, eight new vents opened along the rift zone for 7 km (4 miles) uprift, nearly to Heiheiahulu. The opening was not regular, as with a zipper; instead, the appearance of new vents jumped up and down the rift zone.

A vent between Pu`u Kali`u and Kama`ili fed the Kau`eleau lava flow that entered the ocean between Kehena and `Opihikao. Several vents upslope from the Pahoa-Kalapana road sent lava into a large flow with two tongues, the Kehena and Ke`eke`e flows, that entered the sea at, and just east of, Kehena. In all, 24 main vent areas were active at one time or another during the 88 days of eruption, which ended rather abruptly on May 26.

Next week's column concludes the story of the 1955 eruption with discussions of ground deformation in Puna, Kīlauea's summit deflation, and the societal impacts of an eruption in a populated area.

Volcano Activity Update

A swarm of earthquakes on February 23 outlined an intrusion of magma into the upper east rift zone of Kīlauea Volcano. The earthquakes started at 1:42 p.m., intensified in frequency and magnitude for several hours, then slowly waned through the night. Electronic tiltmeters recorded a deflation of the summit region and an inflation of the rift zone near Pauahi Crater. The intrusion had minimal effects on the eruption at Pu`u `O`o. Lava continues to flow through a system of tubes toward the coast, but numerous breakouts from the Lae`apuki tube system on Pulama pali has reduced the volume of lava reaching the coast. The flow entering the ocean at Lae`apuki was weak and intermittent. The eastern flow located near Waha`ula continues to fill the low areas mauka of the shoreline and is also inflating earlier active flows. There is a major breakout on Pulama pali from the tube system of this eastern flow. The public is reminded that the ocean-entry areas are extremely hazardous, with explosions accompanying unpredictable collapses of the new land. The active lava flows are hot and have places with very thin crust. The steam clouds are highly acidic and laced with glass particles.

Residents of Kona and Hawaiian Ocean View Estates felt an earthquake at 1:14 p.m. on Wednesday, February 23. The magnitude-3.5 temblor was located 2 km (1.2 miles) east of Honaunau at a depth of 15.12 km (9.1 miles). Many of the shallow earthquakes associated with the intrusion into the upper east rift zone of Kīlauea were felt by people in the area. The largest earthquake of the swarm at 2:06 p.m. on February 23 was felt throughout the Volcano community and Hawaii Volcanoes National Park. The magnitude-4.0 temblor was located 7 km (4.2 miles) southeast of the summit of Kīlauea at a depth of 2.34 km (1.4 miles).