HVO Assesses Kilauea’s Explosions, Surges & Pulses

Since the Kilauea eruption in the Lower East Rift Zone (LERZ) began over 12 weeks ago, one constant has been the ever-changing and unpredictable nature of this unprecedented eruption.

Hawaiian Volcano Observatory reports that this is the first eruption of this magnitude in over 200 years.

High levels in the channelized flow and a small spillover from the channel on July 26, 2018, at 6:08 p.m. PC: Crystal Richard

The channelized flow from Fissure 8 below ground level visibility during a fluctuation of the channel level, after being high minutes before which causing small spill overs at Leilani Avenue on July 26, 2018, at 6:18 p.m. Here, the glow along the channel is from the most recent spillover and the inside edge of the channel. PC: Crystal Richard

The channelized flow rising during fluctuations on July 26, 2018, at 6:23 p.m. PC: Crystal Richard

Small overflow from the channelized flow from Fissure 8 on Leilani Avenue on July 26, 2018. at 6:51 p.m. PC: Crystal Richard

The activity at the summit has never been seen before. The closest comparison was the 1924 event, but that did not create an eruption in LERZ, nor was there the series of explosive collapse events.

As of July 28, there have been 60 collapse explosion events at the summit since the eruption began in May. HVO reports a collapse explosion event occurred at 2:37 a.m. July 28, 2018, with an energy release equivalent to a 5.4-magnitude earthquake.

After a collapse explosion at the summit, there is some evidence of a surge from Fissure 8.

Research Geophysicist Ingrid Johanson said while there is surge evidence in Leilani Estates after a collapse event, it hasn’t been fully conclusive; however, there is some evidence and association between the two.

The now dead-end of Ho‘okupu Street in Leilani Estates Subdivision on July 26, 2018. PC: Crystal Richard

Small overflows in the upper portion of the channel have occurred, but the overflows did not exceed the existing flow field.

Johanson said they are unable to predict overflows.

In addition to surges, HVO field crews report fluctuations in the channel level.

“Two things are happening in the lava channel—surges and pulses,” she said. “As far as I know, neither one is fully understood, but USGS scientists are paying close attention to them, trying to sort out the cause(s), explained U.S. Geological Survey HVO Geologist Janet Babb.

“The surges are thought to happen after the summit collapse events, which generate a pressure pulse that seems to somehow have an effect on the Fissure 8 eruption,” she said.

Once a residence on Ho‘okupu Street in Leilani Estates, only the gate and part of the driveway remain. Fissure 8 in the background on July 26, 2018. PC: Scott Cate

Pulses are ongoing, and apparently not related to summit collapse events,” said Babb. “They may have something to do with gases in the lava or lava supply, but it’s still be sorted out. With pulses happening at somewhat regular intervals, it’s really not possible to measure a volume change between
high and low stands of lava.”

A rare angle of Fissure 8 from Ho‘okupu Street in Leilani Estates Subdivision on July 26, 2018. PC: Crystal Richard

Babb said the velocity of the lava flow changes throughout the length of the channel and over time but, measurements have shown that the velocity of the channelized flow is faster closer to the Fissure 8 vent and slower at the distal ends of the channel near the ocean entry. The speed ranges from several meters per second to less than a meter per second.

A rare view of Fissure 8 from Ho‘okupu Street in Leilani Estates on July 26, 2018. PC: Crystal Richard

HVO scientists are under the assumption that as long as lava erupts in the LERZ, the summit can continue to collapse.