Volcano Watch — History of the current eruption

The first 12 years of eruptive activity

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. January 3 marked the twelfth anniversary of the beginning of the eruption. The eruption has consisted of many distinct episodes characterized by activity at different vents and by different eruptive styles. The following summarizes the first 12 years of the eruption, starting with the initial outbreak.

Episodes 1-3: The Initial Fissure Eruption

The eruption began early on January 3, 1983, and, over the next four days, a discontinuous series of fissuresopened along a eight-kilometer-long section in the middle of Kīlauea's East Rift Zone about 16 kilometers from the volcano's summit. Lava fountains became localized along a 1-kilometer-long section of the fissure, where activity continued intermittently for several weeks. The next episode began on February 10 with low-level activity at a new vent, called the 1123-vent for the time of initial activity, and culminated with vigorous fountaining from the same vent between February 25 and March 4, 1983. Episode 3 occurred between March 21 and April 9, with activity at the same vent and at the new O-vent, named for its location on the letter "O" in the word "flow" on the topographic map of the area. This new vent was later renamed Pu'u 'O'o.

Episodes 4-47: Construction of the Pu'u 'O'o Cone

By episode 4, which began on June 13 and ended on June 17, activity had settled at the Pu'u 'O'o vent, located slightly uprift from the 1123 vent. During the next three years, the 255-meter-high Pu'u 'O'o cone 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. By the time the eruption shifted about three kilometers downrift in July 1986, it had covered 40 square kilometers of land.

Episode 48: The Kupaianaha shield

The next vent to form, 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 12 kilometers 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 Hawaii Volcanoes National Park Visitor Center at Waha'ula and an additional 33 homes in Kapa'ahu, lower Royal Gardens, and in the National Park as the flow field widened.

In April 1988, the eruption stopped for one week--the first period of repose since July 1986. A series of 12 brief pauses in the eruptive activity began in Febuary 1990 and continued until November 1990. During the first of these pauses, the tubes feeding lava to the ocean became blocked, and when the eruption resumed, surface flows sent lava once again towards Kalapana. The volume and depth of the active lava in the Kupaianaha 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, Kalapana was overrun, and 100 additional homes were destroyed by tube-fed lava flows.

Upper East Rift Zone intrusions

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. As the level of lava in the tube dropped, collapses of the tube walls and roof formed blockages in the lower reaches of the tube system, and the lava delivered to the ocean near Waha'ula diminished in volume, stopping altogether in early September 1991. As the tube system atrophied over the next two months, the terminus of the tube retreated closer and closer to the vent. In October, two additional homes in Royal Gardens were destroyed by some of the last large surface flows to erupt from Kupaianaha.

Episode 49: A new fissure

On November 8, 1991, the eruption abruptly changed once again, with a curtain of fire erupting from a series of discontinuous fissures between Pu'u 'O'o and Kupaianaha. Episode 49 continued until November 26 and fed 'a'a flows to the top of Royal Gardens but did not reach any of the remaining houses. During and after episode 49, tube-fed pahoehoe flows continued to erupt from nearby Kupaianaha, although their volume was significantly reduced. The episode 49 'a'a flow mainly covered earlier flows from Pu'u 'O'o and Kupaianaha. The volume of lava erupted from Kupaianaha continued to decline after episode 49 until February 6, 1992, when the last sluggish flows from Kupaianaha issued from the tube about 2 kilometers downslope of the vent.

Episode 50: Fissure on the flank of Pu'u 'O'o

On February 17, 1992, a new 150-meter-long fissure opened on the uprift flank of the Pu'u 'O'o cone and formed a large perched pond just north of the rift. This eruptive episode, number 50, lasted until March 3, when the eruption abruptly shut down, coincident with an intrusion in the upper East Rift Zone near Pauahi Crater.

Another upper East Rift Zone intrusion

The seismic swarm associated with the intrusion on March 3, 1992, consisted of nearly 2,400 recorded earthquakes. At the same time, the summit region began to deflate sharply as magma migrated from beneath the summit into the rift zone. As magma intruded into the upper East Rift Zone, the area around Pauahi Crater uplifted, and new ground cracks crossed Chain of Craters Road near Devil's Throat Crater. Measurements made after the intrusion showed a total of 30 centimeters of extension in the Devil's Throat and Pauahi Crater area.

Episode 51: Fissure activity resumed

On March 7, 1992, the episode 50 fissure extended higher on the flank of Pu'u 'O'o, forming several new vents. These vents, called the episode 51 vents, have been active ever since. By the end of 1993, more than a dozen eruptive periods lasting from 8.5 hours to 20 days had been interspersed with repose periods lasting from 3 hours to 6 days.

The episode 51 vents produced a 60-meter-high lava shield against the uprift flank of Pu'u 'O'o. From the base of the shield, a broad flow field extends toward the south. The vents soon settled into a pattern of quiescent effusion with only low-level spattering. A lava pond formed atop the shield early in episode 51. Although it resembled the Kupaianaha pond, which was fed by vents directly beneath it, the 51 pond was fed via a tube leading from vents 50 meters to the east of the pond. By mid-July, the lava tube had bypassed the pond, and it has been empty ever since.

Episode 52 and more of episode 51

A new eruptive fissure on the south flank of the Pu'u 'O'o cone opened on the night of October 2, 1992. The two main vents on the fissure fed a vigorous pahoehoe flow that turned to channeled 'a'a as it advanced to the south. Both the 51 and 52 vents were active for the next three days, and then the 52 vent began to wane. By mid-October, the 52 vents were dead, while 51 continued to erupt.

Following episode 52, the activity became more constant. As a result, the lava tube leading to the south edge of the 51 shield extended in October to the top of the steep slope above the coast, and surface flows advanced rapidly downslope. By November 8, lava had crossed the Chain of Craters Road and entered the ocean at Kamoamoa. In December, virtually all of the lava erupted at the 51 vents was fed directly to the ocean via lava tubes. At the coast, flows buried the Kamoamoa campground, picnic area, and the new black sand beach formed earlier by Kupaianaha flows entering the ocean farther to the east. A new lava delta extended 300 meters out to sea, filling the bay. On the evening of November 24, spectacular steam explosions formed a 8-meter-tall littoral cone where lava entered the sea.

On January 3, 1993, Kīlauea again paused, perhaps to celebrate the tenth anniversary of the eruption, but activity resumed the following day, and by the 5th, the volume was back to normal (50-100,000 cubic meters per day). At about the time of this brief pause in activity, a number of new collapse pits formed on the west flank of Pu'u 'O'o. Late on the night of Feruary 14, magma began to intrude into the upper East Rift Zone near Makaopuhi Crater. Soon afterward, eruption tremor recorded near Pu'u 'O'o decreased in amplitude and by 4 a.m. had reached background levels. A series of steam explosions shook the coastal lava delta as seawater entered the drained tube. The next night, the floor of Pu'u 'O'o collapsed. The eruption would remain shut down for nine days.

Episode 53—and yet more of episode 51

The volume slowly increased after activity resumed on February 16, 1993, but did not reach moderate levels until the 20th, when a new vent opened adjacent to the main episode 52 vent. Fountain heights increased to 15 meters by the following day, and the lava ponded over a broad area at the base of the episode 51 shield. On the 23rd, the ponded lava had overtopped a skylight in the old episode 51 tube, and lava from both the episode 53 and episode 51 vents commingled in this tube and was transported towards the coast. Another small collapse pit formed on the west side of Pu'u 'O'o on February 23.

Throughout the remainder of 1993 and through all of 1994, lava has erupted from both the episode 51 and episode 53 vents and it has flowed to the ocean through the old episode 51 tube. There have been occasional breakouts along the pali, and the tubes near the ocean entries have undergone collapse leading to new surface flows and new ocean entry points. From the beginning of episode 53 until February 1, 1994, the eruption volume was moderate but variable, with high volumes of perhaps 300,000 cubic meters per day and lows of about 150,000.

On April 19, 1993, a visitor to Hawaii Volcanoes National Park was killed when the lava bench he was standing on collapsed into the ocean. The same event injured 22 other visitors when steam explosions scattered incandescent lava blocks on the lava delta by the ocean entry. All the injured visitors and the one person killed were beyond "area closure" signs posted by the National Park Service to keep people safely away from the unstable lava benches along the ocean. During the rest of 1993 and for much of 1994, newly formed lava benches repeatedly collapsed into the ocean.

The past year, the lava system was more stable than the preceding two years and was reminiscent of periods when flows issued from Kupaianaha between mid-1986 and early-1992. There was only a handful of eruptive pauses, and lava was transported in a single tube to the ocean near Lae'apuki for the first 2/3 of the year. However, beginning in August, this tube system began to break down, resulting in numerous surface flows below Pulama Pali and the resurfacing of nearly the entire coastal lava plain near Kamoamoa and Lae'apuki. The year ended with small lava entries near Kamoamoa on the east side of the flow field and large surface flows near the west edge of the flow field. We expect the western flows to enter the ocean within the next few days.

No additional structures have been destroyed in 1992, 1993, or 1994, although more archaeological resources in Hawaii Volcanoes National Park have been buried, particularly at Kamoamoa and Lae'apuki. For most of this period, visitors to Hawaiian National Park have had the opportunity to view active lava flows and lava entering the ocean.

Changes at Pu'u 'O'o

Since the eruption shifted to Kupaianaha in 1986, the Pu'u 'O'o conduit has enlarged from 20 meters to a gaping crater 300 meters across. At the same time, the Pu'u 'O'o cone has been reduced in height by about 20 meters due to collapse of the unstable structure. A lava pond has been active at the bottom of the crater throughout much of the last four years, but no lava flows have originated directly from Pu'u 'O'o since 1986. The active pond occupies about a third of the crater floor and varies in height from about 230 to more than 300 feet below the lowest point on the crater rim. In 1994, the biggest change at Pu'u 'O'o has been the formation of a new collapse pit located on the flank of the cone between the cone and the episode 51 vents. This collapse pit dramatically grew to about 80 meters in diameter in October.

Summary

Since the Pu'u 'O'o-Kupaianaha eruption began 12 years ago, about 1,300 million cubic meters (1.3 cubic kilometers) of lava has erupted. For comparison, Mauna Ulu, the previous longest-lived historic eruption on the East Rift Zone, erupted about 350 million cubic meters of lava between 1969 and 1974.
The eruption has destroyed 181 homes and a number of other buildings, with total losses of about $61 million. As long as the eruption is confined to the episode 51 and 53 vents, it poses no immediate threat to residential areas, but it continues to impact natural resources in Hawaii Volcanoes National Park.

The trends from mid-1991 to early 1993 were towards progressively smaller eruptive volumes and migration of the active vents towards the summit. The activity since February 1993 clearly reversed this trend, and the volumes for most of 1993 were nearly as high as at any previous time. In addition, 1994 has been characterized by even greater eruptive volumes, although the eruption rate appears to be decreasing again, starting in October. The average eruptive rate for 1994 was 400,000 cubic meters per day, or nearly 0.15 cubic kilometers per year. For comparison, the eruption rates earlier in the eruption averaged about 0.10 cubic kilometers per year.

The decreasing volumes towards the end of 1994 and the long period of disorganized lava distribution (lack of tube development) that began in August are similar to the events that preceded the shut-down at Kupaianaha vent early in 1992. If these trends continue, we could see the shutdown of the episode 51 and 53 vents by mid-1994. However, we do not expect that this long-lived eruption will be over when the currently active vents stop. Instead, we suspect that new vents will form, probably near Pu'u 'O'o, but possibly farther up the east rift zone or along the southwest rift zone.