Hawai‘i’s two most active volcanoes share a magma source

Using a nearly 200-year record of lava chemistry from Kīlauea and Maunaloa, earth scientists from the University of Hawai‘i at Mānoa and colleagues revealed that Hawai‘i’s two most active volcanoes share a source of magma within the Hawaiian plume. Their discovery was published recently in the Journal of Petrology. 

“In the past, the distinct chemical compositions of lavas from Kīlauea and Maunaloa were thought to require completely separate magma pathways from the mantle source of each volcano to the surface,” said Aaron Pietruszka, lead author of the study and associate professor in the Department of Earth Sciences in the UH Mānoa School of Ocean and Earth Science and Technology (SOEST). “Our latest research shows that this is incorrect. Melt from a shared mantle source within the Hawaiian plume may be transported alternately to Kīlauea or Maunaloa on a timescale of decades.”

Maunaloa—the largest active volcano on Earth—erupted in 2022 after its longest known inactive period (~38 years). This eruptive hiatus at Maunaloa encompasses most of the ~35-year-long Puʻuʻōʻō eruption of neighboring Kīlauea, which ended in 2018 with a collapse of the summit caldera, an unusually large rift eruption, and lava fountains up to 260 feet tall. 

The study authors emphasize that a long-term pattern of such opposite eruptive behavior suggests that a magmatic connection exists between these volcanoes. Additionally, this magmatic connection between Kīlauea and Maunaloa results in a broad correlation between changes in their lava chemistry.

“For example, during the late 19th century when Maunaloa was more active and Kīlauea was less active, the chemistry of lava from Kīlauea became more “unique” and particular to compositions that are only observed at Kīlauea,” said Pietruszka. “We think this was caused by the transport of mantle-derived melt from the shared source of magma to Maunaloa.” 

From the mid-20th century to around 2010, the opposite occurred. Mauanloa was less active, whereas Kīlauea was highly active. During this time, the chemistry of lava from Kīlauea became more similar to typical lava from Maunaloa. 

“We think this was caused by a change in the transport of mantle-derived melt from a shared source within the Hawaiian plume from Maunaloa to Kīlauea,” Pietruszka added. “In other words, each volcano iteratively becomes more active when it receives melt from the shared source in the mantle and this process causes measurable changes in lava chemistry.” 

Since 2010, the research team has observed a change in lava chemistry at Kīlauea. This change suggests that melt from the shared source is now being diverted from Kīlauea to Maunaloa for the first time since the mid-20th century. 

Forecasting future eruptions

Long-term forecasting of volcanic activity currently relies upon extrapolation of a volcano’s past eruptive record to infer its most likely future behavior. 

“Our study suggests that monitoring of lava chemistry is a potential tool that may be used to forecast the eruption rate and frequency of these adjacent volcanoes on a timescale of decades,” Pietruszka said. “A future increase in eruptive activity at Maunaloa is likely if the chemistry of lava continues to change at Kīlauea.”

The researchers will continue to monitor the changes in lava chemistry at Kīlauea to determine whether their predictions for future changes in eruptive behavior at these volcanoes is correct.