Thursday | July 28, 2016
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Kilauea’s ongoing Puu Oo eruption turns 30

Thursday marked the 30th anniversary of Kilauea’s ongoing Puu Oo eruption. Simplifying the past three decades into a single short article belies the eruption’s complex past. So, let’s just look at the major changes that define Kilauea’s long-lived east rift zone activity.

A series of intrusions and comparatively short-lived eruptions occurred along Kilauea’s east rift zone from the early 1960s through the early 1980s. So, the opening of a new fissure in the same general area Jan. 3, 1983, was expected to follow the same pattern. But, after the eruption had focused at a single spot along the fissure six months later and had begun producing towering lava fountains, it was recognized that this eruption was different.

Located on the second “o” in “Lava flow of 1965” as printed on the U.S. Geological Survey topographic map current in 1983, the Puu “O” pyroclastic cone — later renamed Puu Oo — grew taller with the eruption of each fountain. Eventually reaching a height of 835 feet, Puu Oo loomed above the surrounding landscape. The lava fountains, which occurred about every three weeks and lasted about a day, spawned fast-moving aa flows, some of which destroyed houses in the sparsely populated Royal Gardens subdivision.

In July 1986, the magma conduit beneath Puu Oo ruptured, and the eruption shifted two miles to the east and changed style. Instead of episodic lava fountains, the nearly continuous discharge of lava flows prevailed. A broad, low lava shield named Kupaianaha soon formed, and pahoehoe lava flows crept downslope, eventually reaching the ocean.

The change from fountaining to nearly continuous effusion marked a fundamental change in the development of the Puu Oo flow field and the hazards presented by the eruption. Though they traveled much more slowly, the pahoehoe flows constructed lava tubes as they advanced, slowing the cooling rate of the lava, and permitting flows to reach the more populous coastline. Houses were destroyed on both sides of the widening flow field, including the partial destruction of Kalapana in 1990.

Further devastation was spared when, in February 1992, the Kupaianaha vent died and the eruption shifted to new vents on the southwest flank of the Puu Oo cone. Lava again advanced downslope, constructing new lava tubes and widening the existing flow field, mostly within Hawaii Volcanoes National Park. The southwest flank of Puu Oo was slowly buried by a growing lava shield, which became pockmarked with collapse pits.

In January 1997, the magma conduit west of Puu Oo ruptured, cutting the supply of magma to the ongoing eruption. The floor of Puu Oo’s crater dropped 500 feet, and the west wall of Puu Oo collapsed, forming a deep notch in the cone. A few hours later, lava erupted for about a day from new fissures near Napau Crater, west of Puu Oo.

Three weeks later, the eruption resumed from vents on Puu Oo’s southwest flank, sending new flows downslope through the national park and building new tubes. This activity predominated for the next 10 years — until June 2007, when a brief Father’s Day fissure eruption west of Puu Oo shuffled the deck again. The crater floor of Puu Oo collapsed, and Kilauea entered an eruptive hiatus that ended the following month with the return of lava to Puu Oo.

This change culminated in the opening of the “Fissure D” vent between Puu Oo and Kupaianaha. This vent sent flows to the ocean along Kilauea’s southeast coast for much of the next four years, eventually reaching Kalapana Gardens and destroying three homes.

March 2011 brought another change to Puu Oo and the flow field. As in 1997 and 2007, a brief fissure eruption west of Puu Oo was accompanied by collapse of the Puu Oo crater floor and the subsequent cessation of eruptive activity along the east rift zone. The resumption of activity in late March refilled Puu Oo, and, in September 2011, a new vent opened high on the east flank of the Puu Oo cone. This “Peace Day” vent has since carried lava back to Kilauea’s southeastern coast, where it continues to sporadically enter the ocean today.

The diversity of Puu Oo’s past makes a summary like this challenging. Each new day brings more changes, so all details cannot be included, no matter how exciting. To date, about one cubic mile of lava has been erupted, covering 48 square miles of land and destroying 214 structures. Only time will tell what the next 30 years has in store.

Kilauea activity update

A lava lake within the Halemaumau Overlook vent produced nighttime glow visible from the Jaggar Museum overlook and via HVO’s webcam during the past week. Deflation at Kilauea’s summit, likely the start of a deflation-inflation cycle, began Monday and was ongoing as of Thursday. The lava lake level dropped in response, leading to small collapses from the rim of the lake.

On Kilauea’s east rift zone, surface lava flows remain active on the coastal plain near the eastern boundary of Hawaii Volcanoes National Park. Lava is entering the ocean on both sides of the boundary. Within Puu Oo, glow and small, sporadic lava flows emanate from openings in the northeastern, northwestern and southeastern parts of the crater floor.

There were two felt earthquakes reported on the Island of Hawaii in the past week. At 5:24 p.m. Dec. 30, a magnitude 2.9 earthquake occurred four miles west of Kailua-Kona at a depth of 21 miles. At 6:15 a.m. Thursday, a magnitude 2.8 earthquake occurred six miles east of the Mauna Kea summit at a depth of 16 miles.

Visit for Volcano Awareness Month details and Kilauea, Mauna Loa and Hualalai activity updates, recent volcano photos, recent earthquakes and more; call 967-8862 for a Kilauea summary; email questions to

Volcano Watch is a weekly article and activity update written by scientists at the U.S. Geological Survey’s Hawaiian Volcano Observatory.