Last week we discussed the change in seismicity that has occurred at Kilauea. The increased number of earthquakes along the upper east rift zone has also been accompanied by inflation of the summit, Puu Oo and parts of the east rift zone between the two locations. Inflation began in earnest at the start of October, about the same time as the increased earthquake activity, and was shown by GPS and tiltmeter data — viewable at hvo.wr.usgs.gov/kilauea/update/deformation.php — that monitor changes in the shape of the volcano.
Fundamentally, the inflation is caused by a disparity in Kilauea’s magma budget — that is, more magma enters the volcano than is erupted. This means that either the amount of magma supplied to the volcano has increased, the amount erupted has decreased or both.
A similar disparity may have prompted Kilauea’s March 2011 Kamoamoa fissure eruption. The start of inflation at the summit, Puu Oo and parts of the east rift zone and rising summit lava level in Halemaumau, beginning in late 2010 and comparable to what is occurring now, were indications of more magma coming into the volcano than was being erupted. The inflation rate increased until March 5, 2011, when the 41⁄2-day-long Kamoamoa fissure eruption occurred between Napau Crater and Puu Oo. The eruption disturbed the east rift zone plumbing system; eruptive events occurred in August and September 2011. Steady lava effusion returned to Puu Oo, but the eruption rate has still not returned to pre-2010 values.
The increased rate of inflation extending from the summit to Puu Oo in the past month has been accompanied by continued, but slow, advance of a narrow lava flow across the coastal plain. A possible increase in this activity, though hard to measure, may be evidence of a small increase in eruption rate despite the constriction in Puu Oo.
Not only was the 2011 Kamoamoa eruption preceded by inflation, but similar to what is occurring now, there was also a major increase in the number of earthquakes along the upper east rift zone, as well as a rise in the level of the lava lake at Kilauea’s summit. Given the parallels between 2011 and today, some are wondering if we are on the path to a new eruptive event at Kilauea.
If current activity continues, the answer is probably yes. Kilauea cannot erupt all of the magma that is coming in to the volcano, resulting in a buildup of pressure. This pressure can only be relieved by a decrease in the magma supply coming into the volcano, an increase in the eruption rate at Puu Oo, or an intrusion into south Kilauea Caldera or one of Kilauea’s rift zones, which may or may not culminate in the opening of a new eruptive vent.
If a new vent opens, where might it be? Past patterns suggest that new activity will probably occur somewhere along the east rift zone between the summit and near Puu Oo. We continue to record a high level of seismic activity beneath the summit caldera and within the upper east rift zone centered beneath Kokoolau Crater. While this has been a typical seismic pattern over the past 50 years, historical eruptions have not occurred there but were located either uprift — west of Lua Manu and within the south summit caldera — or downrift, between Hiiaka Crater and Puu Oo. Since 1983, many new vents have formed in the vicinity of Puu Oo.
Eruptions along the southwest rift zone and the lower east rift zone downrift of Puu Oo are less common historically. That is not to say, however, that eruptions cannot or will not happen in those places. Indeed, future eruptions will eventually occur in all parts of Kilauea’s rift zones and summit area — the reason why HVO maintains a robust monitoring network across the entire volcano.
Perhaps the best lesson of the current inflation, seismicity and lava level rise is that it pays to be vigilant. Kilauea is giving warning signs of a potential change in eruptive activity, allowing everyone to prepare for that eventuality. The scientists at HVO are currently busy making measurements and deploying additional instruments to best track the evolving activity, which will teach us more about how Kilauea works.
Kilauea activity update
A lava lake within the Halemaumau Overlook vent produced nighttime glow visible from the Jaggar Museum overlook and by HVO’s webcam during the week. The lava lake reached a new high level about 72 feet below the floor of Halemaumau Crater Oct. 26. Cracking and booming noises, caused by thermal fracturing of the vent wall, continued to emanate sporadically from the vent.
On Kilauea’s east rift zone, surface lava flows are still accumulating at the base of the Pulama pali within the abandoned Royal Gardens subdivision. The flows reached within 0.8 mile of the shoreline Monday and continued to advance slowly. Within the Puu Oo crater, the northeastern pit still holds a circulating lava lake. Occasional flows were erupted from a pit on the southern side of the crater floor.
No earthquakes were reported felt across Hawaii Island during the past week.
Visit hvo.wr.usgs.gov for detailed Kilauea, Mauna Loa and Hualalai activity updates, recent volcano photos, recent earthquakes and more; call 967-8862 for a Kilauea summary; email questions to askHVO@usgs.gov.
Volcano Watch is a weekly article and activity update written by scientists at the U.S. Geological Survey’s Hawaiian Volcano Observatory.