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Time-lapse movie of Pu‘u ‘O‘o Crater

This thermal image shows an overview of active surface flows Thursday (Nov 1). There was a small area of active surface flows near the top of the pali, at the top of Royal Gardens subdivision, but most of the surface flows were active on the coastal plain. A line of high temperatures coming down the pali reveals the path of the lava tube, which splits just above the base of the pali. Photo courtesy of USGS/HVO

(Volcano Watch is a weekly article written by scientists at the U.S. Geological Survey’s Hawaiian Volcano Observatory.)

This view towards the southeast shows the vent area and upper lava tube system. In the lower right is Puʻu ʻŌʻō crater, with a small circular lava lake in the northeast portion of the crater floor. Just to the left of this lava lake, outside of the crater on the eastern spillway, is the area of the September 21, 2011, fissure which is now the vent for the Peace Day flow. The vent area, now covered in lava, is the start of the lava tube, whose subsurface path is marked by the many sources of white fume. Photo courtesy of USGS/HVO

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, Pu`u `O`o, 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 that monitor changes in the shape of the volcano (these data can be viewed at http://hvo.wr.usgs.gov/kilauea/update/deformation.php).

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, Pu`u `O`o, and parts of the east rift zone and rising summit lava level in Halema`uma`u, beginning in late 2010, were indications of more magma coming into the volcano than was being erupted (comparable to what is occurring now). The inflation rate increased until March 5, 2011, when the 4.5-day-long Kamoamoa fissure eruption occurred between Napau Crater and Pu`u `O`o. The eruption disturbed the east-rift-zone plumbing system, and several months passed, during which eruptive events occurred in August and September 2011. Steady lava effusion returned to Pu`u `O`o, but the eruption rate has still not returned to pre-2010 values.

The increased rate of inflation extending from the summit to Pu`u `O`o 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 Pu`u `O`o.

Lava spatters above the Kamoamoa fissure just west of Pu`u `O`o cone in March 2011. Photo courtesy of USGS/HVO

Not only was the 2011 Kamoamoa eruption preceded by inflation, but 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—similar to the activity that is occurring now. Given the parallels between 2011 and today, the question everyone is asking is: Are we 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 Pu`u `O`o, 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 Pu`u `O`o. We continue to record a high level of seismic activity beneath the summit caldera and within the upper east rift zone centered beneath Koko`olau 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 Hi`iaka Crater and Pu`u `O`o. Since 1983, many new vents have formed in the vicinity of Pu`u `O`o.

Eruptions along the southwest rift zone and the lower east rift zone (downrift of Pu`u `O`o) 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.