Volcano Watch: Looking back at the 1959 episodic eruption of Kīlauea Iki

“Volcano Watch” is a weekly article and activity update written by U.S. Geological Survey Hawaiian Volcano Observatory scientists and affiliates. Today’s article is by HVO geologist Katie Mulilken.

A series of lava fountains building a cone perched on the crater rim … sounds like the ongoing eruption in Halemaʻumaʻu Crater at the summit of Kīlauea, right? But that description could also fit the 1959 Kīlauea Iki eruption.

Let’s compare these two episodic lava fountaining eruptions.

An earthquake swarm 35 miles beneath Kīlauea in August 1959 was followed in October by ground swelling, indicating magma was accumulating within the volcano.

Kīlauea summit region shook for 5 hours Nov. 14 that year as magma made a path to the surface. The eruption began at 8:08 p.m. as a series of small lava fountains on the south wall of Kīlauea Iki Crater, east of Kaluapele — the summit caldera of Kīlauea.

Gradually, during the next day, eruptive activity became focused at one vent.

That vent continued to erupt for the next week, with lava fountains reaching up to 1,200 feet high. Fallout from the lava fountain — tephra, or fragments from volcanic eruptions that are ejected through the air — landed on the crater rim to the southwest, while lava also accumulated within the crater, forming a lava lake.

The lava lake within the crater rose above the level of the vent Nov. 21. That evening, the vent abruptly stopped erupting and lava from the lake began to drain back.

During the next 5 days, pāhoehoe ooze outs and crustal overturns continued on the lava lake surface within the crater. The vent crusted over, but the eruption was not finished.

Just after midnight Nov. 26, the eruption resumed.

Similar to how some episodes of the ongoing Halemaʻumaʻu Crater eruption at the summit have been slow to start, Episode 2 in 1959 started with low fountains as degassed lava that drained into the vent was erupted out.

Eventually, eruption of fresher and gassier lava was accompanied by higher lava fountains reaching 1,000 feet. The second episode lasted less than 24 hours.

In total, 17 episodes of lava fountaining occurred at Kīlauea Iki throughout about a month.

Episode 15 even saw the highest lava fountains ever recorded at Kīlauea: 1,900 feet. Tephra fell up to 10 miles downwind. Puʻupuaʻi was built as 230 feet of tephra piled on the crater rim, while the crater was filled with 413 feet of lava.

During the ongoing Halemaʻumaʻu eruption, 140 feet of tephra has accumulated on the crater rim and an average of 223 feet of lava has been added to the crater floor.

When lava would drain back after an episode in 1959, it left a “black ledge” — like a bathtub ring — around the crater. During early episodes of the current ongoing eruption in Halemaʻumaʻu, drainback similarly occurred, but this no longer occurs because the vent topography is now much higher than the surroundings.

Following recent episodes in Halemaʻumaʻu, the cone on the crater floor and rim developed large cracks as portions of the steep and unconsolidated slopes slump downward. This also occurred in 1959, with collapsed parts of the cone being rafted on the lava lake surface during subsequent episodes.

During the monthlong Kīlauea Iki eruption, 13.2 billion gallons of lava erupted during 17 episodes. About four times that volume — 52.7 billion gallons — erupted during the ongoing Halemaʻumaʻu eruption throughout the course of a little more than twice the number of episodes, but over the course of an entire year.

The ongoing Halemaʻumaʻu eruption has surpassed Kīlauea Iki in terms of longevity and erupted volume, but its lava fountains — at a maximum of 1,575 feet so far — have not yet approached the highest observed during the Kīlauea Iki eruption.

The last two episodes of the Kīlauea Iki eruption occurred the morning and evening of the same day.

Episode 16 produced fountains up to 800 feet, while Episode 17 only produced spatter reaching about 100 feet. This quick drop off in activity is one scenario for how the current Halemaʻumaʻu eruption could end.

After the Kīlauea Iki eruption, the summit region was at a higher level of inflation than before the eruption, leading to magma migration and an eruption on the East Rift Zone in early 1960.

Hawaiian Volcano Observatory does not see any signs of change now to the current eruption, and we continue to closely monitor Kīlauea.

VOLCANO ACTIVITY UPDATES

KĪLAUEA

Volcano Alert Level: Watch

Kīlauea has erupted episodically since Dec. 23, 2024, within Halemaʻumaʻu Crater in the summit caldera.

Episode 39 lava fountaining happened for 6 hours Dec. 23-24, 2025. Lava fountains erupted from the north and south vents, with maximum heights of about 1,400 feet. No unusual activity has been noted along Kīlauea’s East Rift Zone or Southwest Rift Zone.

WHAT’S NEXT? The summit is reinflating; another lava fountaining episode is likely between Jan. 10 and 14.

MAUNA LOA

Volcano Alert Level: Normal.

Mauna Loa is not erupting.

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

EARTHQUAKES

One earthquake was reported felt in the Hawaiian Islands during the past week:

• MAGNITUDE-3.4 located 6 miles east of Pāhala at a depth of 19 miles at 10 p.m. New Year’s Day, Jan. 1.

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 questions to askHVO@usgs.gov.