1960 Kapoho Eruption provided lesson in Kīlauea behavior
The 1960 Kapoho eruption and its predecessor, the 1959 summit eruption in Kīlauea Iki Crater, together formed a summit-flank sequence that was once considered a model for how Kīlauea "should" behave—though it has misbehaved ever since. The Kapoho eruption caused havoc in lower Puna, which was considered an idyllic rural paradise until the lava fountains and flows covered farm land and villages.
Earthquakes and large fault ruptures heralded a devastating eruption
The eruption in Kīlauea Iki had ended on December 21, 1959, but the shallow reservoir beneath the summit of Kīlauea volcano was gorged with magma, far more than before the eruption started. Rather than removing pressure, the eruption had, for all intents and purposes, created more.
During the last week of the year, tiny earthquakes were recorded at the seismograph in Pahoa, some 40 km (25 mi) down the east rift zone from Kīlauea's summit. After quieting down for a week, more than 1,000 earthquakes were recorded on January 12. HVO seismologists used a portable seismograph to pinpoint the source of the swarm as an area just north of Kapoho village, 47 km from the summit.
The size and frequency of the earthquakes increased sharply in the darkness of early morning on January 13. By daybreak the ground was severely cracked through town, along the trace of the Kapoho fault. The ground shook, and fault ruptures caused loud booming sounds. The roughly 300 residents undertook voluntary evacuation.
The Kapoho fault forms the southeast side of the Kapoho graben, a downdropped block within and parallel to the east rift zone. The Koa‘e fault forms the northwest side of the graben. By afternoon, the graben had dropped more than 1 m (3 ft) along the Kapoho fault through town and 1.2 m (4 ft) along the Koa‘e fault.
Eruption began with lava fountains that fed voluminous ‘a‘ā flows
At 7:35 p.m. January 13, red glow in the night sky above Kapoho announced the 1960 eruption. Lava fountains as high as 100 m (330 ft) erupted along a 900-m-long (3,000 ft) fissure within the graben, only 600 m (2,000 ft) northwest of Kapoho. Within a few hours, activity waned at both ends of the fissure as fountain heights grew in the middle and fed ‘a‘ā lava flows to the northeast.
The first night was wrought with loud blasts. Methane explosions occurred as lava consumed vegetation. As groundwater flowed into the conduits and flashed to steam, violent blasts tore the conduits into pieces and shot them upward into billowing steam clouds.
By noon on January 14, the steam blasts had ended and lava fountaining was confined to several sources along a 200-m-long section of the fissure. Fallout from the fountains rapidly built a spatter rampart that opened on the northeast side, where lava continued to feed ‘a‘ā flows.
Over the course of the following week, lava fountains concentrated down to a few vents and sent tephra more than 300 m high. The rampart and cone continued to grow while feeding flows that spread toward the sea and throughout the graben, claiming favorite recreation sites.
After traveling 3.2 km, lava flows reached the ocean on January 15. Before the end of the day, new land extended 100 m beyond the old shoreline. Flows moved southward to slowly consume Higashi Pond over the course of four days (Jan 19 map). Warm Springs, a swimming and picnic area along the Kapoho fault, was overrun by lava flows even after bulldozers scraped together a 450-m-long, 1.5-3-m-high rock dike with the hope of diverting the lava flow.
Barriers were built in an attempt to divert lava flows
Kapoho village was near the eruptive activity, but it was uphill from the fissure. The papaya, coconut, orchid, and coffee groves were taking a beating from the heavy pumice fallout as well as the lava itself, and outlying homes and farmsteads had been destroyed. More destruction was soon to come.
Barriers were built in an attempt to stop the lava flows before they could inundate a school, Coast Guard facilities, and residences. Two barriers were easily shoved aside and overtopped by ‘a‘ā flows. A third barrier, more than 5 m (15 ft) high along its 450 m (500 ft) length, was constructed along the high saddle between the western base of Pu‘u Kūkae and Kapoho Crater, just northwest of Kapoho School. ‘A‘ā flows began piling up behind the wall early in the morning of January 28, and they thickened to more than 15 m (50 ft) above pre-eruption ground level in a few hours. The resulting high pressure caused lava to dislodge a 150-m- (500-ft-) long piece of the uncompacted Pu‘u Kūkae cinder cone. The breach provided a pathway for lava to flow beyond the barrier and Kapoho School was destroyed. The barrier itself remained intact, and it survived until February 5, when it was finally overtopped and almost totally buried by lava that had completely encircled Pu‘u Kūkae. This flow eventually covered the Kapoho cemetery.
On January 21, construction began on a 1.6 km (1 mi) long barrier along a broad forested ridge that stretched nearly to the ocean. The hope was that lava would neither engulf Kapoho Beach Lots nor the Coast Guard facilities at Cape Kumukahi. The wall held back lava for about a week. However, flows eventually breached it in several spots and destroyed the Coast Guard residences, but the lighthouse was spared. During the night of February 3-4, lava destroyed six houses in the Kapoho Beach Lots before the flow ceased early on February 5.
Kapoho and Koa‘e villages fell victim to lava flows.
The Koa‘e fault was overtopped by lava flows on January 18, and Koa‘e town to the north was in jeopardy. Day by day the lava moved closer and closer. It finally surged forward at noon on January 23 to claim a house, community hall, and church in the next four hours. Another house and one more building were destroyed before the flow ceased moving on about January 28.
For the first two weeks, Kapoho village remained virtually intact except for a blanket of pumice and ash that covered everything. The lava flow issuing from the growing cinder cone was moving in the opposite direction of town. Things changed on January 27th when very fluid lava poured from the vents and fed massive ‘a‘ā flows that moved southwestward through the streets of town. By midnight on January 27, most of Kapoho had been destroyed.
Lava temperatures and fountain heights soared in the last weeks of the eruption.
During the night of January 30-31, lava fountain temperatures were 20-50 degrees Celsius (about 70-130 F) higher than most earlier measured temperatures. This coincided with a period of narrow, high fountains that lasted the day. It was later discovered that a batch of hotter magma from Kīlaueas summit had mixed with cooler magma that had been stored in a reservoir beneath the Kapoho area since 1955 or earlier.
High fountains continued until February 15, when lava was spraying upward from the main vent area to heights of 300 m (1,000 ft). But the vigor and discharge of the eruption were, in general, steadily declining until the morning of February 19, when the eruption stopped.
When the eruption was all over, lava flows covered more than 10 km2 (4 mi2), including 2 km2 (0.75 mi2) of new land beyond the original shoreline (see final map). The volume of lava erupted is conservatively estimated as 122 million m3 (160 yd3) with an additional 7.5 million m3 (10 yd3) of pyroclastic material.
Changes at Kīlauea's summit occurred throughout and past the end of the eruption.
On January 17, four days after the Kapoho eruption had started, the summit began to subside (deflate, by analogy with a balloon) and tilt inward, apparently as magma was leaving the storage reservoir and heading down the east rift zone to the Kapoho area. Most of the deflation had taken place by the time the eruption ended, but it tailed off gradually until the summer.
Small, shallow earthquakes were recorded beneath Kīlaueas summit by January 23. By the end of the month, thousands of earthquakes occurred each day and hundreds could be felt. Larger earthquakes occurred on February 12 and March 7 causing respective damage to Hilina Pali Road and residences in the Park and Volcano Village.
Collapse of Halema‘uma‘u Crater floor began during the night of February 6-7, 1960 and continued until March. A lava lake had been cooling in the crater since its eruption in 1952, and the subsidence formed cracks in its cooling shell both above and below a still liquid interior. Surface cracks provided a pathway for viscous lava to pour into the growing pit from a ring fracture. On March 11, the final collapse of the Halema‘uma‘u crater floor occurred, and the total volume of collapse was about 22 million m3 (29 million yd3).