Pu`u `O`o wraps up 24th year of eruption

January 3 will mark the 24th anniversary of Kilauea’s longest rift-zone eruption in the last 600 years, but some people still aren’t impressed. If we had a dime for every time we’ve heard a visitor ask, “When is the volcano going to erupt?,” we wouldn’t be rich, but we’d definitely have enough for a big slab of ahi at New Year’s prices.

As it is, we just sigh and launch into our usual explanation. The volcano is erupting, we say, but it’s not the kind of eruption you were expecting.

For obvious reasons, TV stations and the tourist industry give heavy play to video footage and photographs from the early years of this eruption, when lava fountains as high as 460 m (1,500 ft) burst from Pu`u `O`o every three to four weeks. In those days, people tried to time their trip to Hawai‘i to see a fountaining episode, and many succeeded. The collective memory of those towering fountains refuses to fade, and, as a result, many visitors are surprised and a little disappointed to find out that Pu`u `O`o got all that out of its system 20 years ago.

Episodic high fountaining lasted from June 1983 through June 1986, building a cinder-and-spatter cone 255 m high. `A`a flows fanned out through native rain forest and overran houses in Royal Gardens subdivision.

In the summer of 1986, the eruption shifted to a new vent, named Kupaianaha, 3 km (1.9 mi) downrift. Kupaianaha was the site of continuous eruption for the next 5.5 years.

The eruption changed its style as well as its location, becoming less exuberant with age. Episodic lava fountains were replaced by quiet, steady effusion.

Lava reached the ocean in November 1986, traveling through lava tubes most of the way. Vog became an island issue as the continuous activity produced a pall of sulphurous air that has been with us ever since.

The section of Highway 130 that linked the coastal section of Hawai`i Volcanoes National Park with Pahoa was closed for good in early 1987. The community of Kapa`ahu, the park’s visitor center at Waha`ula, most of Royal Gardens, and finally the village of Kalapana were overrun and buried by lava.

By early 1991, the output of Kupaianaha had begun a steady decline, and in February 1992, Kupaianaha stopped erupting. Eleven days later, a fissure opened on the west flank of Pu`u `O`o. This marked the beginning of an era of flank-vent activity on the Pu`u `O`o cone that continues today.

The eruption has deviated from Pu`u `O`o only once since 1992, when fissures in and near Napau Crater, uprift of Pu`u `O`o, erupted for about 22 hours in January 1997. During most of the last 14 years, tube-fed lava flows have reached the coast within Hawai`i Volcanoes National Park, with a few brief excursions beyond the eastern boundary of the park.

The total area covered by lava since 1983 is 118 square kilometers (46 square miles), and the volume of erupted lava is 3 cubic km (0.7 cubic miles).

The past year has been relatively quiet, with lava flows mostly recoating older flows from this eruption. Lava entered the ocean all year at East Lae`apuki, which was the site of the largest bench collapse (54 acres) in the history of the eruption in November 2005. This year, however, the bench has held its own, and is now 59 acres in area.

In May, the Campout flow split off from the prevailing Kuhio (PKK) tube and reached the ocean at East Ka`ili`ili in August. The Campout flow is still the source of intermittent surface flows on the pali and coastal plain, but unfortunately for visitors and residents alike, lava viewing this year has generally required a long hike. The Campout flow covered only about 32 acres of vegetated land in 2006, most of which was in several kipuka on the pali. The flow also encroached on a smidgeon (less than 5 acres) of lower Royal Gardens.

In 1983, none of us expected that the eruption would outlive our careers, but that is beginning to happen. Retirement begins next week for Civil Defense assistant administrator Lanny Nakano, who has worked with us on the eruption for many years. Aloha Lanny!

Activity Update

This past week, activity levels at the summit of Kilauea Volcano have remained at background levels. The number of earthquakes located in the summit area is low (usually less than 10 per day that are large enough to locate).

Eruptive activity at Pu`u `O`o continues. On clear nights, glow is visible from several vents within the crater. The PKK and Campout tubes feed two widely separated ocean entries, at East Lae`apuki and East Ka`ili`ili, respectively.

In the last week, intermittent breakouts from the Campout tube have occurred on the slope of Pulama pali and on the coastal plain. On December 20, an arm of the Campout flow reached the ocean at Kamokuna, about midway between the two main entries. The new entry lasted less than a day, but started up again on December 26.

Access to the sea cliff near the ocean entries is closed, due to significant hazards. The surrounding area, however, is open. If you visit the eruption site, check with the rangers for current updates, and remember to carry lots of water when venturing out onto the flow field.

There were three earthquakes beneath Hawai`i Island reported felt within the past week. A magnitude-2.1 earthquake occurred at 12:12 p.m. H.s.t. on Sunday, December 24, and was located 11 km (7 miles) southeast of Hawi at a depth of 26 km (16 miles). A magnitude-2.2 earthquake occurred at 8:56 a.m. on Monday, December 25, and was located 6 km (4 miles) south of Pahoa at a depth of 4 km (3 miles). A magnitude-2.8 earthquake occurred at 4:15 p.m. on the same day, and was located 2 km (4 mile) northwest of Waiki`i at a depth of 33 km (21 miles).

Mauna Loa is not erupting. During the past week, earthquake activity remained low beneath the volcano’s summit (two earthquakes were located). Extension of distances between locations spanning the summit, indicating inflation, continues at slow rates.

This article was written by scientists at the U.S. Geological Survey’s Hawaii Volcano Observatory and is republished by HawaiiNews.com with permission.

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