Thursday marked the 30th anniversary of Kilauea’s ongoing Pu‘u ‘O‘o 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 on 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 Pu‘u “O” pyroclastic cone — later renamed Pu‘u ‘O‘o — grew taller with the eruption of each fountain. Eventually reaching a height of 835 feet, Pu‘u ‘O‘o loomed above the surrounding landscape. The lava fountains, which occurred about every three weeks and lasted about a day, spawned fast-moving ‘a‘a flows, some of which destroyed houses in the sparsely populated Royal Gardens subdivision.
In July 1986, the magma conduit beneath Pu‘u ‘O‘o ruptured, and the eruption shifted 2 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 Pu‘u ‘O‘o 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 Pu‘u ‘O‘o 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 Pu‘u ‘O‘o was slowly buried by a growing lava shield, which became pockmarked with collapse pits.
In January 1997, the magma conduit west of Pu‘u ‘O‘o ruptured, cutting the supply of magma to the ongoing eruption. The floor of Pu‘u ‘O‘o’s crater dropped 500 feet, and the west wall of Pu‘u ‘O‘o 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 Pu‘u ‘O‘o.
Three weeks later, the eruption resumed from vents on Pu‘u ‘O‘o’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 the brief Father’s Day fissure eruption west of Pu‘u ‘O‘o shuffled the deck again. The crater floor of Pu‘u ‘O‘o collapsed, and Kilauea entered an eruptive hiatus that ended the following month with the return of lava to Pu‘u ‘O‘o.
This change culminated in the opening of the “Fissure D” vent between Pu‘u ‘O‘o and Kupaianaha. This vent sent flows to the ocean along Kilauea’s southeast coast for much of the next 4 years, eventually reaching Kalapana Gardens and destroying three homes.
March 2011 brought another change to Pu‘u ‘O‘o and the flow field. As in 1997 and 2007, a brief fissure eruption west of Pu‘u ‘O‘o was accompanied by collapse of the Pu‘u ‘O‘o crater floor and the subsequent cessation of eruptive activity along the East Rift Zone. The resumption of activity in late March refilled Pu‘u ‘O‘o, and, in September 2011, a new vent opened high on the east flank of the Pu‘u ‘O‘o 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 Pu‘u ‘O‘o’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 4 cubic kilometers (~1 cubic mile) of lava have been erupted, covering 48 square miles of land and destroying 214 structures. Only time will tell what the next 30 years have in store.
A lava lake within the Halema‘uma‘u Overlook vent produced nighttime glow that was 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 (DI) cycle, began on Monday, Dec. 31, and was ongoing as of this writing on Thursday.
The level of 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 side of the boundary.
Within Pu‘u ‘O‘o, 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. On Dec. 30 at 5:24 p.m., a magnitude-2.9 earthquake occurred 4 miles west of Kailua-Kona at a depth of 21 miles. On Jan. 3 at 6:15 a.m., a magnitude-2.8 earthquake occurred 6 miles east of Mauna Kea summit at a depth of 16 miles.
Visit the HVO website (http://hvo.wr.usgs.gov) 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 askHVO@usgs.gov.
Volcano Watch (http://hvo.wr.usgs.gov/volcanowatch/) is a weekly article and activity update written by scientists at the U.S. Geological Survey‘s Hawaiian Volcano Observatory.