Kīlauea’s summit is shaped like a series of steps, and the deepest part—Halemaʻumaʻu—collapsed in 2018, creating a large void. Since then, five eruptions between 2020 and 2023 have filled in about a quarter of that space, raising the crater floor more than 1,300 feet, which is about equal to the height of the Empire State Building. Over the past year and a half, the ongoing episodic lava fountaining eruption has added even more lava, bringing the total to roughly 60% of the 2018 collapse now filled. 

If the current eruption continues at the same pace, the volume that collapsed in 2018 could be almost completely filled by late 2027. After that, lava would begin spilling onto the main caldera floor—something we haven’t seen in over 50 years. 

But filling the main part of the caldera will take much longer: many, many years.  

There’s another twist: the active vents are still about 200 feet below the crater rim in Halemaʻumaʻu. If they continue to grow higher and reach above the crater rim, lava could flow downslope out of the caldera and to the southwest, staying within Hawaiʻi Volcanoes National Park and posing no threat to communities. Or, depending on vent geometry, lava could keep filling the caldera. Whichever way lava flows, it will be down the path of least resistance. 

So, the simplest answer to whether lava will flow out of the caldera is: it depends—on how long this eruption lasts, how much lava is produced, and whether new activity starts somewhere else on Kīlauea. 

For now, the eruption at the summit continues. Episode 51 occurred on July 15. More time and monitoring is needed to forecast episode 52 but it’s looking likely within the coming weeks.  

Mahalo for listening, I’m Katie Mulliken and this was your weekly volcano minute brought to you by the USGS Hawaiian Volcano Observatory.