Volcano Watch — Eruption's 10th year begins

Nine years ago on January 3, 1983, the ongoing eruption on the East Rift Zone of Kīlauea Volcano began when a discontinuous 3.7-mile long series of fissures opened in, and downrift of Napau Crater. 

As we begin the tenth year of this eruption, the volume of lava being erupted is at a very low level. However, the summit continues to inflate with new magma, as it has since the end of episode 49 in November. The U.S. Geological Survey predicts that the Kupaianaha vent will stop erupting altogether in the near future and that the eruption will shift to a new location and perhaps become episodic once again.

The Pu`u `O`o-Kupaianaha eruption now ranks as the longest-lived historic eruption on the East Rift Zone and the most destructive in Kīlauea's recent history. By episode 4 in June 1983, the eruption settled at the Pu`u `O`o vent. During the next three years, the 835-foot high Pu`u `O`o vent was constructed by 44 episodes of high-fountaining, most lasting less than a day. `A`a flows from Pu`u `O`o repeatedly entered the Royal Gardens subdivision in 1983 and 1984 and destroyed 16 residences. Before the eruption shifted about two miles downrift in July 1986, it covered 16 square miles of land. 

The new vent, Kupaianaha, was characterized by continuous, quiet effusion of lava. A lava pond formed over the new vent, and its overflows built a broad, low shield. After weeks of eruption, the channel leading from the pond roofed over, forming the beginning of a tube that would reach the ocean, nearly seven-and-one-half miles away by December 1986. These tube-fed flows destroyed 11 homes in sparsely populated Kapa`ahu; a separate flow to the east destroyed an additional 17 homes in the more densely populated Kalapana Gardens subdivision. 

Over the next several years, lava continued to enter the ocean through a complex and changing network of tubes, destroying the National Park Visitor Center at Waha`ula and an additional 33 homes in Kapa`ahu, lower Royal Gardens, and Hawai`i Volcanoes National Park as the flow field widened. 

In April 1988, the eruption paused for one week - the first period of repose since July 1986. A series of 12 eruptive pauses began in February 1990 and continued until November 1990. During the first of these pauses, the tubes feeding lava to the ocean became blocked, and lava headed once again towards Kalapana. The size and depth of the Kupaianaha lava pond steadily diminished during early 1990, and by June 1990 the pond was empty. Lava flowed directly from the vent into the tube system without being visible on the surface. By the end of 1990, all of Kalapana was overrun and 100 additional homes were destroyed. 

In December 1990, and again in March and August 1991, magma from the summit intruded into the upper East Rift Zone, but with little effect on the ongoing eruption at Kupaianaha. By the middle of 1991, the volume of lava erupted at Kupaianaha began to decrease. Breakouts from the tube system occurred in August between 600- and 1,100-foot elevations, and the volume of lava delivered to the ocean near Waha`ula diminished. The tube system stopped feeding lava directly into the ocean by September 6, 1991. Surface flows coated the pali from the coastal plain to about the 1,500-foot elevation just east of Royal Gardens in September and October. In October, two additional homes in Royal Gardens were destroyed. 

On November 8, 1991, the eruption abruptly entered a new phase, with a curtain of fire erupting from a series of discontinuous fissures between Pu`u `O`o and Kupaianaha. This event, episode 49, continued until November 26 and fed `a`a flows to the top of Royal Gardens, but did not destroy any additional homes. Throughout eruptive episode 49 and after it was over, lava continued to erupt from nearby Kupaianaha, although the volume was significantly reduced. The episode 49 flow covered earlier flows from Pu`u `O`o and Kupaianaha.

The only surface flows currently active are being fed from a breakout from the tube system at about the 1,900-foot elevation. The mainly pahoehoe flows erupted from Kupaianaha covered 15 square miles of land, 2 of which were previously covered by flows from Pu`u `O`o. The flows that reached the ocean also added about 300 acres of new land to Hawai`i.

Throughout much of the last several years, an active lava pond has been visible inside the Pu`u `O`o Crater, but no lava flows have overflowed the crater since the Kupaianaha vent formed in 1986. During that time, the Pu`u `O`o cone has been reduced in height by about 65 feet due to collapse of the unstable structure. The conduit within the cone has also enlarged from 65 feet to a gaping crater nearly 800 feet across.

The eruption has now destroyed 181 homes, the Visitor Center at Waha`ula, the Royal Gardens community center, the Mauna Kea Congregational Church, the Puna Canoe Club halau, and the Kalapana Drive-In, with total losses of about $61 million. This has been the most destructive eruption of Kīlauea Volcano and it is not over yet. 

Since the eruption began, about 1,800 million cubic yards of lava have erupted. In comparison, Mauna Ulu, the previous longest-lived historic eruption on the East Rift Zone, erupted only about 400 million cubic yards of lava between 1969 and 1974. The geologic history of the lower and middle East Rift Zone recorded by prehistoric lava flows suggests that more eruptions are highly likely to occur in this area, even after this eruption is over. Such future eruptions pose even greater hazards, as the area has developed rapidly since the last eruption of the lower East Rift in 1960.