Kīlauea’s summit has been erupting intermittent lava fountains since December 23rd, 2024, producing 52 episodes of lava fountains so far—some shooting more than 1,700 feet into the air, taller than the Empire State Building in New York City. But why do these fountain heights rise and fall? 

Scientists are looking into the magma itself for answers. 

Each fountain episode sends tiny bits of cooled lava—called tephra—into the air. Inside that tephra are clues about the magma’s chemistry. One key indicator is magnesium oxide. Higher levels of magnesium oxide mean hotter, fresher magma while lower levels of magnesium oxide tells us the magma has cooled and started a process called differentiation before it was erupted. 

Most episodes in the ongoing Kīlauea summit eruption so far have shown similar chemistry, suggesting a steady supply of fresh magma under Halemaʻumaʻu. But recently, scientists spotted a new population of olivine crystals in episode 44, showing lower magnesium. That hints that the magma had time to cool, possibly because less new magma was flowing into the chamber. 

Since then, both magnesium oxide levels and fountain heights have begun to rise again, signaling that magma supply may be picking back up—and Kīlauea could be entering another period of growing lava fountain heights. 

As the eruption continues, Hawaiian Volcano Observatory scientists will continue to track these chemical clues in near-real time to better forecast what Kīlauea could do next. 

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