(BIVN) – Kīlauea volcano remains in a precursory phase – at this point the longest precursory phase of the current eruption – with a pause in visible lava activity Monday morning.
Overnight, there were nearly continuous spatter bursts at the north vent, where a spatter cone has been formed. The spatter activity started around 6:30 pm HST, and intensified, featuring larger bursts of 35-70 feet (10-20 m) high. Tremor was constant and slow summit inflation continued.
The activity stopped at sunrise Monday morning.
The USGS Hawaiian Volcano Observatory said Sunday that the “onset of episode 55 fountaining is likely today or tomorrow, if conditions remain favorable.”
Summit inflation remains well above the episode 54 starting level. “Inflation-based forecasting models are no longer valid and it is difficult to say how long this precursory activity may last,” the Observatory stated.
Previously, the longest period of precursory activity was 6.2 days, which occurred before episode 44.
The USGS Volcano Alert Level remains at WATCH and the Aviation Color Code is ORANGE.
From the lengthy “Summit Observations” section of the Monday activity update written by the USGS Hawaiian Volcano Observatory:
Intermittent spatter bursts became visible in the north vent early yesterday morning and increased in intensity throughout the day. Around noon, the bursts began depositing spatter that built a small cone on the rim of the north vent. Initial bursts resembled splashing of fluid lava within the vent. As the afternoon progressed, eruptive activity cooled lava (making it more viscous or sticky) within the upper regions of the conduit. This change allowed gas to coalesce into larger and larger bubbles driving bigger bursts of spatter cooling the lave even more. This produced a distinct Strombolian style of eruption throughout the night charactered by large individual spatter bursts one after another like fireworks, in contrast to the continuous eruption of lava in Hawaiian style lava fountains. Eruptions of spatter slowed this morning and there have been very few spatter bursts since 6 a.m. HST. Glow, flames and occasional spatter were also visible in the south and west vents overnight, and two small residual lava flows were visible oozing out lower on the north vent shield-structure overnight.
This is now the longest precursory period (6.8 days) since high fountains began after episode 4. The longest period of precursory activity was 6.2 days before episode 44 and the most overflows record was 179 from the north and south vents combined prior to episode 36.
Weak spattering from the north vent was first reported at 6:54 p.m. HST on September 6. Sluggish precursory overflows from the north vent started at around 12:45 p.m. HST on September 7 with no dome fountains or spattering. Overflows from the north vent continued intermittently after that, with a total of 104 between September 7 and 12. Overflows lasted from a few minutes to about 2 hours long and were separated by interludes of about 15 minutes to 8 hours. Overflows between September 7-9 became progressively more vigorous and were fed by a dome fountain that reached 15-30 ft (5-10 m) tall. Two main lava flows formed during these overflows with one making it about a half mile (1 kilometer) to the southwest of the north vent, and the other making it less than half a mile (1 kilometer) to the northeast of the north vent. On September 10, overflows were generally sluggish, less frequent, shorter in duration (less than ten minutes), not fed by a dome fountain, and did not travel as far from the north vent. Overflows on September 11-12 showed more vigor and lasted longer than ten minutes, with dome fountains that grew from 15-30 ft (5-10 m) to 35-50 feet (10-15 m) tall and generated lava flows that traveled farther from the north vent than on September 10. Overflows from September 7-12 built a small shield around the north vent which has since been capped by a spatter cone built from strombolian activity over the past day.
Tremor recorded at Kīlauea’s summit has remained relatively uniform and continuous over the past 24 hours, possibly reflecting the stable position of magma close to the surface within all 3 vents. Tremor intensity did not vary appreciably with eruptive activity. Over the past 24 hours, 13 small earthquakes were recorded beneath the summit region mostly surrounding Halemaʻumaʻu. This includes a small swarm of earthquakes around 9:20 p.m. HST that lasted for about 10 minutes just north of the active vents. Similar numbers of earthquakes have occurred over the past Recent earthquakes have not been closely clustered in space or time and are probably related to the general increase in pressure in the shallow Halemaʻumaʻu magma chamber.
Summit reinflation has been very unsteady since lava fountaining episode 54 on August 25. On September 7 around 3:00 p.m. HST, inflation at UWD reached a maximum that was higher than when episode 54 began, approximately 13.2 microradians. Following this inflationary high, UWD recorded around 1 microradian of deflation with the onset of precursory lava flows from the north vent. From then on, there was little net change until around 9 p.m. HST on September 10, when slow inflation returned. As of this morning, UWD is inflation remains stalled since stopping at about 9 p.m. HST. The total inflationary tilt measured on the UWD tiltmeter remains over two microradians above the 12.7 microradians lost during episode 54.
During inter-episode pauses, the sulfur dioxide (SO2) emission rate from the summit typically varies between 1,000 and 5,000 tonnes per day. Light trade winds (less than 10 mph (5 meters per second) are pushing the degassing plume to the southwest of Kīlauea’s summit caldera this morning are expected to continue. Models indicate that gases as well as fine ash and Pele’s hair would be transported to the south of Kaluapele if episode 55 fountaining were to begin today.
