The eruption in Kilauea Iki had ended on December 21, but the shallow reservoir beneath the summit of Kilauea volcano was gorged with magma. Rather than removing pressure, the eruption had, for all intents and purposes, created more.
The end of 1959 was an uneasy time for the staff at the Hawaiian Volcano Observatory. During the last week of the year, a swarm of earthquakes started in Pāhoa (more than 1,000 earthquakes were recorded by the Pāhoa station on January 12.)
The 1960 Kapoho eruption and its predecessor, the 1959 summit eruption in Kilauea Iki Crater, together formed a summit-flank sequence. The Kapoho eruption caused havoc in lower Puna, an idyllic rural community until the lava fountains and flows covered farm land and villages.
The size and frequency of the earthquakes increased; at 8 am, January 13, the ground was severely cracked along the fault through Kapoho town. Movement along the fault was literally pulling the town apart.
The ground was constantly shaking. The roughly 300-residents undertook voluntary evacuation, which was completed by early evening. At 7:35 pm, January 13, 1960, a red glow above Kapoho confirmed the start of the eruption.
Within half an hour, fountaining was nearly continuous along a nearly ½ – mile long fissure. After a couple hours, the activity focused with central fountains – for the next 11-hours powerful steam blasts roared from the vents.
The resulting fallout coated everything with a thin film of fine, wet, glassy ash. Salt crystals formed as the water evaporated; they testified to the brackish nature of the groundwater.
By noon on January 14, the steam blasts had ended and lava fountaining was confined to many sources along a 650-foot long section of the fissure. An ʻaʻa flow, 18-feet thick and nearly 1,000-feet wide reached the ocean – a bench formed 300-feet beyond the old shoreline.
In an attempt to save Warm Springs, bulldozers pushed a rock dike; shortly after, lava overtopped it and filled the pool.
Kapoho, a bit uphill of the fissure, was near all this activity but had not been touched by lava. Pumice and lava were wreaking havoc on nearby homes and farms (papaya, coconut, orchid and coffee groves.)
ʻAʻa continued to enter the ocean; it was also spreading southward. Bulldozers worked in forming a barrier to protect Kapoho, Kapoho School, an area of expensive homes and real estate at Kapoho Beach Lots. By January 20, lava had reached the barrier and overtopped it on January 23; a second barrier was shoved aside on January 27.
A third barrier held the flow, but lava then moved underground, beneath the end of the barrier, emerging near Kapoho School. The buildings began to burn at 10 am and the school was lost shortly after noon.
The barrier itself remained intact, and it survived until February 5, when it was finally overtopped and almost totally buried by lava that eventually covered the Kapoho cemetery. More coastal houses were lost.
Despite notable developments in the vent area, Kapoho village remained virtually intact except for a blanket of pumice and ash that covered everything.
For seven hours on the afternoon of January 27, the heaviest pumice fall of the entire eruption rained down on the area during strong kona winds.
However, it was the lava flow that would doom the town.
Late that night, the rapidly moving ʻaʻa flow moved through the streets, overwhelmed building after building. By midnight January 27, most of Kapoho had been destroyed; a couple days later (January 30) the town was gone.
The eruption ended slowly. Dribbles of lava continued to enter the sea north of Cape Kumukahi as late as February 13. High fountains continued until February 15, when lava was spraying upward from the main vent area to heights of 600-feet. It gradually subsided and on the morning of February 19, the eruption stopped.
Volcanologists concluded that the Kapoho eruption was tied to events at Kilauea’s distant summit. On January 17, four days after the Kapoho eruption had started, the summit began to subside (deflate, by analogy with a balloon) as magma was leaving the storage reservoir and heading down the east rift zone to the Kapoho area.
The eruption was the first during the modern era of volcano monitoring at Hawaiʻi Volcanoes Observatory. As a result, probably more fundamental ideas were reached from it than from any other single eruption in Hawaiʻi.
The main lesson, and really the only one that bears repeating over and over again, is clear. What happened then will happen again. That lesson should never be lost. (All information here is from USGS.)