Volcano Watch: Kīlauea all tied up at 47 episodes

“Volcano Watch” is a weekly article and activity update written by U.S. Geological Survey Hawaiian Volcano Observatory scientists and affiliates.

Lava fountains that erupted a week ago Thursday, May 14, marked the 47th episode of the ongoing Halemaʻumaʻu Crater episodic eruption at the summit of Kīlauea volcano on the Big Island.

That episode tied the 1983-86 initial phase of the Pu‘u‘ō‘ō eruption, which had a total of 47 events, for the most fountaining episodes ever recorded at Kīlauea. Now that we’ve reached this milestone, let’s dig a bit deeper into how these historic eruptions compare.

Both eruptions produced spectacular high fountains, as did the 1959 Kīlauea Iki eruption with 17 episodes and the 1969-70 Maunaulu eruption with 12 episodes.

Similar high fountains were also associated with the 1960 Kapoho eruption, but this was driven by continuous draining of the summit reservoir at lower elevation vs. the cyclic refilling that produces episodic eruptions higher on Kīlauea.

The current Halemaʻumaʻu eruption is clearly a historic event, providing the kind of close access to these classic Hawaiian fountain events not seen since the 1959 Kīlauea Iki eruption, which only lasted 1 month.

Very few people got to see the Pu‘u‘ō‘ō fountains because of the eruption’s remote location in the middle of Kīlauea’s East Rift Zone.

Inevitably, the question always comes up: “How does this eruption compare to past eruptions? Is it bigger, higher, longer?”

These questions can be tricky to answer as eruptions differ in style, and the way we collect data changed throughout the past decades. Even though the current Halemaʻumaʻu eruption and initial part of the Pu‘u‘ō‘ō eruption reached 47 episodes, the current eruption took 1.5 years — more than twice as fast as the 3.5 years it took Pu‘u‘ō‘ō to reach the same mark.

The average pause between episodes ranged from 24 days for Pu‘u‘ō‘ō, about 18 days for Maunaulu, 10 days for the ongoing Halemaʻumaʻu eruption to a remarkable 2 days between Kīlauea Iki fountain events.

The magma supply rate for the Pu‘u‘ō‘ō eruption was about 4.6 cubic yards per second, similar to the long-term supply rate from the hot spot to Kīlauea. The preliminary supply rate for the Halemaʻumaʻu eruption is about 5.8 cubic yards per second, or 25% more than the long-term supply rate.

The Kīlauea Iki eruption has long been known to have been fed by an unusual pulse of deep magma that averaged a little greater than 20 cubic yards per second, about 5 times the long-term average supply rate.

Height is another way to compare these eruptions (naturally).

Kīlauea Iki — as of now — still holds the record of just greater than 1,900 feet for the highest fountain. The record fountain height was short-lived and lasted only about 10 minutes.

How fountain height is measured matters though.

Scientists during the Pu‘u‘ō‘ō eruption measured the highest wisps of incandescent lava, while we have been measuring the maximum height of the sustained, dense fountains in Halemaʻumaʻu, which can be several hundred feet lower than the wisps.

Whether or not the Halemaʻumaʻu eruption produced a fountain greater in height than the Kīlauea Iki eruption will take some dedicated sleuthing. However, Episode 43 produced a 1,770-foot fountain from the south vent and a 1,440-foot fountain from the north vent, a truly magnificent spectacle not seen in prior eruptions.

More than half of the Halemaʻumaʻu episodes have had dual fountains, which is also another aspect that sets this eruption apart.

The episodic high fountaining of Pu‘u‘ō‘ō built a towering cone greater than 800 feet high that was visible from Hilo, and unlike any other vent ever described on Kīlauea or Mauna Loa volcanoes.

This landmark was short-lived. The cone was being incrementally swallowed into its own vent system by the 1990s, explaining why there were no others.

The current Halemaʻumaʻu eruption has built a cone at its peak has added 150 feet to the elevation of the crater rim, making it about equal in elevation above sea level to the peak of Puʻupuʻai, the cinder cone built by the 1959 eruption.

However, the vent height has built up more than 500 feet from the floor of Halemaʻumaʻu Crater, where it began in December 2024.

The ongoing episodic summit eruption is already an event for the history books, garnering worldwide attention because of its visibility and access.

No doubt, years from now, today’s kids will be telling their grandchildren about these fountains.

VOLCANO ACTIVITY UPDATES

KĪLAUEA volcano

VOLCANO ALERT LEVEL: Advisory

Kīlauea has erupted episodically since Dec. 23, 2024, within the summit caldera. Episode 47 of lava fountaining happened for 9 hours May 14-15. No unusual activity is noted along Kīlauea’s East Rift Zone or Southwest Rift Zone.

WHAT’S NEXT: Summit region inflation since the end of Episode 47 indicates another fountaining episode is possible. Models currently indicate Episode 48 is most likely to begin between May 24 and 26.

MAUNA LOA volcano

VOLCANO ALERT LEVEL: Normal

Mauna Loa is not erupting. Visit the Hawaiian Volcano Observatory website for the latest monthly update for Mauna Loa.

Hawaiian Volcano Observatory continues to closely monitor Kīlauea and Mauna Loa.

EARTHQUAKES

Two earthquakes were reported felt during the past week in the Hawaiian Islands:

• MAGNITUDE-2.9 earthquake at 4:19 p.m. May 18 located 6 miles west of Kalaʻoa at a depth of 5 miles.
• MAGNITUDE-3.0 earthquake at 8:36 a.m. May 15 located at 6 miles southwest of Hāwī at a depth of 16 miles.

Visit the Hawaiian Volcano Observatory website for past “Volcano Watch” articles, Kīlauea and Mauna Loa updates, volcano photos, maps, recent earthquake information and more. Email to askHVO@usgs.gov with any questions.