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 Pu‘u ‘O‘o eruption.
In fact, calculations show, 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 Kahauale‘a 2 lava flow, which has been active since May 2013. Moreover, cycles of deflation and inflation (DI events), which occur frequently at Kilauea’s summit, repeatedly disrupt the supply of magma reaching Pu‘u ‘O‘o, causing the amount of lava feeding the Kahauale‘a 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 Kahauale‘a 2 flow during the past year. This pattern of diminished momentum has important implications for communities downslope from the flow.
Initially, the Kahauale‘a 2 flow advanced to the north, traveling 3.2 kilometers (2 miles) before it stalled during a major disruption in lava supply in late July 2013.
The flow restarted again closer to Pu‘u ‘O‘o in early August and made sporadic forward movement until late November 2013, when its front stalled 7.3 kilometers (4.5 miles) northeast of Pu‘u ‘O‘o.
By this time, a relatively well-established lava tube had developed up to about 5 kilometers (3 miles) northeast from the vent, marking the limit to which the flow retreated.
When the flow resumed days later, it slowly reached 7.8 kilometers (4.8 miles) northeast of Pu‘u ‘O‘o before stalling again in January.
Following the same “two steps forward, one step back” pattern, the flow front reached 8.3 kilometers (5.2 miles) from the vent by early April before its movement was disrupted again.
The Kahauale‘a 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 Pu‘u ‘O‘o 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 Pu‘u ‘O‘o.
Sustained flows also topped much of the south rim of the crater, burying much of the southern flank of the Pu‘u ‘O‘o cone beneath a carapace of new lava.
This period of heightened activity came to a sudden end 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 Pu‘u ‘O‘o quickly stagnated, and the forward momentum of the Kahauale‘a 2 flow was disrupted after it reached 8.8 kilometers (5.5 miles) northeast of Pu‘u ‘O‘o .
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 Kahauale‘a 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 7.0 kilometers (4.3 miles) from the vent.
With the current pressurized state of Kilauea, and especially with the lack of much pressurization at Pu‘u ‘O‘o , we can’t help but wonder whether it wi