For the past several years, the amount of lava erupting from Kilauea’s East Rift Zone has been well below the long-term output rate established earlier in the Puu Oo eruption. In fact, calculations show that, since 2010, only about half as much lava is being erupted at any given time as before. The reason for this is unknown; maybe it is a consequence of the opening of Kilauea’s summit eruptive vent in 2008 or perhaps it is a natural variability in the amount of magma arriving beneath the volcano from the Earth’s mantle.
Nevertheless, the result has been less surface activity than “usual.” This continues to be evident with the Kahaualea 2 lava flow, which has been active since May 2013. Moreover, cycles of deflation and inflation, which occur frequently at Kilauea’s summit, repeatedly disrupt the supply of magma reaching Puu Oo , causing the amount of lava feeding the Kahaualea 2 flow to fluctuate dramatically.
The combination of these two factors — low effusion rate and repeated disruptions — has resulted in the erratic forward movement of the Kahaualea 2 flow over the past year. This pattern of diminished momentum has important implications for communities downslope from the flow.
Initially, the Kahaualea 2 flow advanced to the north, traveling 2 miles before it stalled during a major disruption in lava supply in late July 2013. The flow restarted again closer to Puu Oo in early August and made sporadic forward movement until late November 2013, when its front stalled 4.5 miles northeast of Puu Oo. By this time, a relatively well-established lava tube had developed up to about 3 miles northeast from the vent, marking the limit to which the flow retreated.
When the flow resumed days later, it slowly reached 4.8 miles northeast of Puu Oo before stalling again in January. Following the same “two steps forward–one step back” pattern, the flow front reached 5.2 miles from the vent by early April before its movement was disrupted again.
The Kahaualea 2 lava flow advanced yet again through late April and early May. This period, however, was accompanied by more profound pressurization within the magma chamber beneath Kilauea, as indicated by summit inflation and extension, which led to a relatively high lava level within the lava lake at Kilauea’s summit.
In the east rift zone, the increased pressure manifested itself as — or was reflected in — new lava flows from several spatter cones on the floor of the Puu Oo crater. This renewed filling of the crater brought lava to within just a few yards of Hawaiian Volcano Observatory webcams and other equipment positioned on the north rim of Puu Oo. Sustained flows also topped much of the south rim of the crater, burying much of the southern flank of the Puu Oo cone beneath a carapace of new lava.
This period of heightened activity came to a sudden end on May 10 when an abrupt deflation and increase in seismicity at Kilauea’s summit marked the release of summit pressurization, likely a result of the intrusion of magma beneath the surface just south of the volcano’s summit. New lava flows within and around Puu Oo quickly stagnated, and the forward momentum of the Kahaualea 2 flow was disrupted after it had reached 5.5 miles northeast of Puu Oo.
Since late May, the summit of Kilauea has been inflating once again, reaching a pressurization state similar to that prior to the May “intrusion.” The summit lava lake has also risen to a level comparable to its level in early May. Despite this, the Kahaualea 2 flow has been even weaker than before, suggesting a fundamental change in the magmatic plumbing system. A handful of small breakouts, spread along the well-established lava tube within the flow, have crept forward since then, but as of mid-June, had reached only 4.3 miles from the vent.
With the current pressurized state of Kilauea, and especially with the lack of much pressurization at Puu Oo, we can’t help but wonder whether it will result in another small intrusion beneath Kilauea’s summit, or perhaps in something even more significant, such as the March 2011 Kamoamoa fissure eruption along the volcano’s east rift zone. Then again, it may lead to nothing.
No matter how the current conditions on Kilauea play out, scientists at the Hawaiian Volcano Observatory will continue to monitor the volcano’s every move and will keep you informed about the Kahaualea 2 flow through daily eruption updates at hvo.wr.usgs.gov/activity/kilaueastatus.php.
Kilauea activity update
A lava lake within Halemaumau produced nighttime glow that was visible via HVO’s webcam during the past week. The lava lake level rose slightly, reaching about 118 feet below the rim of the overlook crater by Thursday.
On Kilauea’s east rift zone, the Kahaualea 2 flow remains active. The flow front stalled at 5.5 miles northeast of its vent on Puu Oo in mid-May. On Tuesday, the most distant active flows were 4.3 miles northeast of Puu Oo. In addition, several small spatter cones within the Puu Oo crater continued to produce glow.
There was one earthquake reported felt in the past week. On Tuesday at 6:05 p.m, a magnitude-2.4 earthquake occurred 2.5 miles southwest of Captain Cook at a depth of 8 miles.
Visit hvo.wr.usgs.gov for 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.
