Pu'u 'Ō'ō

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Puʻu ʻŌʻō
View at dusk, June 1983
Elevation	2,290 ft (698 m)
Location	Hawaii, USA
Range	Hawaiian Islands
Coordinates	19°23′11″N, 155°06′18″W
Topo map	USGS Kalalua
Type	Cinder cone
Age of rock	< 21 years
Last eruption	current

Puʻu ʻŌʻō (which means "Hill of the ʻŌʻō Bird" in Hawaiian, is often written as Puu Oo, and is roughly pronounced "Poo-oo Ohh-ohh" or [puʔu ʔoːʔoː] in the IPA) is a cinder/spatter cone in the eastern rift zone of the Kīlauea volcano of the Hawaiian Islands. Puʻu ʻŌʻō has been erupting continuously since January 3, 1983, making it the longest-lived rift-zone eruption of the last two centuries. From 1983 through 1998, lava from Puʻu ʻŌʻō covered more than 97 km² (37 square miles).

As of 1998, the eruption had claimed 181 houses, as well as a church, a store, the Wahaʻula Visitor Center, and many ancient Hawaiian sites. The coastal highway has been closed since 1987, as lava flows covered 13 km (8 miles) to as great a depth as 25 m (80 ft). The eruption has added 544 acres (2.2 km²) of land to the island of Hawaiʻi.

[edit] Puʻu ʻŌʻō-Kūpaʻianahā eruption

The Puʻu ʻŌʻō eruption began when fissures split the ground in the remote rainforest of the eastern rift zone. By June 1983, the activity had strengthened and localized to the Puʻu ʻŌʻō vent. Over the next three years, 44 eruptive episodes with lava fountains as high as 460 m (1500 ft) stopped traffic at points across east Hawaiʻi. The fallout of cinder and spatter from the towering lava fountains built a cone 255 m (835 ft) high. In July 1986, the conduit feeding magma to Puʻu ʻŌʻō ruptured, and the eruption abruptly shifted 3 km downrift to form the Kūpaʻianahā 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 Kūpaʻianahā reached the ocean, 12 km (7 miles) to the southeast, inundating the small community of Kapaʻahu in its path. For the next five years, much of the lava erupted from Kūpaʻianahā streamed directly into the sea via a lava tube system that led from the lava pond.

In 1990, the eruption entered its most destructive phase when flows turned eastward and totally destroyed the villages of Kalapana and Kaimū. Kaimū Bay and Kalapana Black Sand Beach were also completely covered with lava. 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 Hawaii Volcanoes National Park. The volume of lava erupted from Kūpaʻianahā declined steadily through 1991, and in early 1992 the vent died. The eruption then returned to Puʻu ʻŌʻō, 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 in between. The flank vents have held center stage ever since, with the exception of a two-month pause in activity early in 1997 that followed a brief fissure eruption in Napau Crater, a short distance southwest of Puʻu ʻŌʻō.

Cutaway of Puʻu ʻŌʻō January 1997.

On the evening of January 29, 1997, a series of earthquakes struck Kilauea's east rift zone. Deep within the rift zone, magma was escaping from the conduit leading to the Puʻu ʻŌʻō vent, cutting off the supply to the ongoing eruption. The lava pond at Puʻu ʻŌʻō drained, and residents 10 miles (16 km) away heard a low, rumbling roar as the crater floor dropped 500 feet (150 m) and the west wall of the Puʻu ʻŌʻō cone collapsed. A few hours later, as magma found a new path to the surface, the ground cracked in nearby Napau Crater, and lava fountains lit up the night sky.