# Volcano Watch — The longest Kīlauea eruption in memory

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What is the longest eruption in memory at Kīlauea? The ongoing Puu Oo-Kupaianaha eruption, which entered its 18th year on January 3? The nearly continuous activity of Halemaumau in the 19th century, remembered so vividly in many writings? Well, arguably it was an eruption in the 15th century, which just may be memorialized in the Pele-Hiiaka chant.

What is the longest eruption in memory at Kīlauea? The ongoing Puu Oo-Kupaianaha eruption, which entered its 18th year on January 3? The nearly continuous activity of Halemaumau in the 19th century, remembered so vividly in many writings? Well, arguably it was an eruption in the 15th century, which just may be memorialized in the Pele-Hiiaka chant.

This eruption has recently been studied by a team of scientists led by Dave Clague, ex-Scientist-in-Charge of HVO. The 'Ailaau eruption, as it is called, took place from a vent area just east of Kīlauea Iki. The eruption built a broad shield, the shape of which is apparent when viewed from the overlook at Jaggar Museum. The eastern part of Kīlauea Iki Crater slices through part of the shield, and red cinder and lava flows near the center of the shield can be seen on the northeastern wall of the crater.

The eruption probably lasted about 50 years, from about 1420 to 1470. Clague and his colleagues arrived at these dates by carefully evaluating radiocarbon data for 17 samples of lava flows produced by the Ailaau shield. Previous columns have described how charcoal--created when lava burns vegetation--can be used to date flows. The ages obtained for the 17 samples were averaged and examined statistically to arrive at the final results. The new age is 100-200 years older than previously thought but is more consistent with what has been learned since those estimates were made.

The radiocarbon data are supported by the magnetic declination and inclination of the lava flows, frozen into the flows when they cooled. This study found that these "paleomagnetic directions" are very different than those of older and younger flows and consistent with what was expected for the 15th century.

Such a long eruption naturally produced a large volume of lava, estimated to be about 5.2 cubic kilometers (1.25 cubic miles) after accounting for the bubbles in the lava. The rate of eruption is about the same as that for other long-lasting eruptions at Kīlauea.

This large volume of lava covered a huge area, about 430 square kilometers (166 square miles). From the summit of the Ailaau shield, pahoehoe lava flows moved 40 km northeastward, making it all the way to the coast at Kaloli Point and at a number of other places from near Kalele to beyond Opihi Rock. Another lava flow headed south from the Ailaau shield, crossing Ainahou Ranch and reaching the south coastline between Apua Point and Keauhou Landing. Much of the lava was transported in tubes away from the shield.

Lava covered all, or most, of what are now Mauna Loa Estates, Royal Hawaiian Estates, Hawaiian Orchid Island Estates, Fern Forest Vacation Estates, Eden Rock Estates, Crescent Acres, Hawaiian Acres, Orchid Land Estates, Ainaloa, Hawaiian Paradise Park, and Hawaiian Beaches. The pahoehoe flows did leave rather large kipuka south of Keaau and in the forest southwest of Ainaloa, as well as small kipuka in Hawaiian Paradise Park and elsewhere.

Such a vast outpouring changed the landscape of much of Puna. It must have had an important impact on local residents, and as such it may well be described in the Pele-Hiiaka chant. Hiiaka, late on returning to Kīlauea from Kauai with Lohiau, sees that Pele has broken her promise and set afire Hiiaka's treasured ohia lehua forest in Puna. Hiiaka is furious, and this leads to her love-making with Lohiau, his subsequent death at the hands of Pele, and Hiiaka's frantic digging to recover the body. The Ailaau flows seem to be the most likely candidate to have covered so much of Puna that they were worthy of commemoration in the chant. The timing seems right, too--after the Pele clan arrived from Kahiki, before the caldera formed (Hiiaka's frantic digging may record this), and before the encounters with Kamapuaa, some of which probably deal with explosive eruptions between about 1500 and 1790.

### Volcano Activity Update

Eruptive activity of Kīlauea Volcano continued unabated during the past week. Lava is erupting from Puu Oo and flowing through a network of tubes toward the coast. A flow has been entering the ocean at Laeapuki since mid-December 1999, and a second flow is now entering the ocean near Wahaula. The public is reminded that the ocean-entry areas are extremely hazardous, with explosions accompanying unpredictable collapses of the new land. The active lava flows are hot and have places with very thin crust. The steam clouds are highly acidic and laced with glass particles.

Two lobes of the flow located near the eastern boundary of the National Park are burning trees in a kipuka on Pulama pali and providing visitors to Hawaii Volcanoes National Park with a memorable view at night. The distal end of this flow reached the ocean on February 3, 2000.

A magnitude-4.1 earthquake was widely felt at 11:33 p.m. on Thursday, January 27. No report of damages was received from the residents of Ka`u, Puna, Hilo, Hamakua, and Kona where the temblor was reported felt. The earthquake was located 8 km (4.8 mi) north of Pahala at a depth of 11.3 km (6.8 mi).