Volcano Watch — Eruption at Pu‘u ‘Ō‘ō marks 15th anniversary

Saturday marked the 15th anniversary of the Pu‘u ‘Ō‘ō-Kupaianaha eruption on the east rift zone of Kīlauea Volcano. This is the longest lived rift zone eruption of the last two centuries and as of yet shows no signs of stopping.

During the last decade-and-half, a broad shield of lava has buried over 37 square miles of the volcano's south flank, and flows entering the ocean have added more than 560 acres of new land to the island. The eruption has claimed 181 houses, as well as a church, a store, the WAHULA visitor center, and many ancient Hawaiian sites. The coastal highway has been closed for 11 years as flows resurfaced the road.

The Pu‘u ‘Ō‘ō-Kupaianaha eruption began innocuously on Jan. 3, 1983, when fissures split the ground and released curtains of lava in the remote rainforest and lava fields of the middle east rift zone. This was the way many eruptions in the preceding 20 years had begun; nothing foretold the impact that this eruption would have. 

By June 1983, the activity had localized at the Pu‘u ‘Ō‘ō vent, and for the next three years, 44 eruptive episodes with lava fountains as high as 1,500 feet stopped traffic at vantage points across east Hawai‘i. During this period, the eruption settled into an increasingly regular pattern of brief eruptive episodes, each lasting less than 24 hours and separated by repose periods averaging 25 days. The fallout of cinder and spatter from the towering lava fountains built a cone 835 feet high.

In July 1986, the conduit feeding magma to Pu‘u ‘Ō‘ō ruptured, and the eruption abruptly shifted downrift to form the Kupaianaha vent. With the new vent came a new style of eruption. Continuous, quiet effusion from a lava pond replaced the episodic high fountaining. Overflows from the pond built a lava shield—a broad, low hill shaped like an overturned wok. In November 1986, lava from Kupaianaha reached the ocean, seven miles to the southeast, inundating the small community of Kapa‘ahu in ints path. For the next five years, much of the lava erupted from Kupaianaha streamed directly into the sea via a lava tube system that led from the lava pond.

In 1990, the same eruption entered its most destructive phase when flows turned eastward and flooded the village of Kalapana. Over 100 homes were destroyed by the ever-broadening flow field in a nine-month period. New tubes diverted lava away from Kalapana early in 1991, and lava once again entered the ocean within the national park.

The volume of lava erupting from Kupaianaha declined steadily through 1991, and, in early 1992, the vent died. The eruption then returned to Pu‘u ‘Ō‘ō, where flank vents on the west and southwest sides of the cone constructed a new lava shield. Soon lava tubes were feeding lava from the vents to the ocean, with few surface flows between. The flank vents have held center stage ever since, with the exception of a two-month pause in activity in 1997 that followed a brief fissure eruption in Napau Crater, a short distance southwest of Pu‘u ‘Ō‘ō.

What does the future hold? The longevity of the current eruption is unique in the brief era of scientific observation at Kīlauea. On the timescale of millennia, however, long-lived eruptions have probably played a significant part in building the volcano. So we offer a word to the wise: Don't place any bets on this eruption ending anytime soon!

Volcano Activity Update

Eruptive activity from the vent within Pu‘u ‘Ō‘ō increased last Tuesday, and the elevated lava pond cast a warm glow visible on the fume clouds overhead. Gentle wind conditions combined with a high output of sulfur dioxide led to the closure of several Hawai‘i Volcanoes National Park facilities during the past week due to the poor air quality. Lava continued to flow through a network of tubes down to the seacoast where it entered the ocean at two locations—Waha‘ula and Kamokuna. The public is reminded that the ocean entry areas are extremely hazardous, with explosions accompanying frequent collapses of the lava delta. The steam cloud is highly acidic and laced with glass particles.

There were no earthquakes reported felt during the past week.