UH researchers: Hawai‘i’s two most active volcanoes share magma source

Using a nearly 200-year record of lava chemistry from Kīlauea and Mauna Loa on the Big Island, scientists from University of Hawaiʻi at Mānoa and their colleagues revealed that Hawaiʻi’s two most active volcanoes share a magma source within the Hawaiian plume.

Their discovery was published in the Journal of Petrology.

“In the past, the distinct chemical compositions of lavas from Kīlauea and Mauna Loa were thought to require completely separate magma pathways from the melt source in the mantle beneath each volcano to the surface where eruptions take place,” said Aaron Pietruszka, lead author of the study and associate professor in the Department of Earth Sciences at the University of Hawaiʻi at Mānoa School of Ocean and Earth Science and Technology. “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 Mauna Loa on a timescale of decades.”

From the mid-20th century to about 2010, Mauna Loa was less active, whereas Kīlauea was highly active. During this time, the chemistry of lava from Kīlauea became more similar to typical lava from Mauna Loa.

“We think this was caused by a change in the transport of mantle-derived melt from a shared source within the Hawaiian plume from Mauna Loa 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 melt from the shared source is now being diverted from Kīlauea to Mauna Loa for the first time since the mid-20th century.

Mauna Loa — the largest active volcano on Earth — erupted in 2022 after its longest known inactive period of nearly 400 years.

This eruptive hiatus encompasses most of the about 35-year Puʻuʻōʻō eruption of neighboring Kīlauea, which ended in 2018 with a collapse of the summit caldera, an unusually large lower East Rift Zone eruption that destroyed more than 700 structures and lava fountains up to 260 feet tall.

The authors of the study emphasize that a long-term pattern of such opposite eruptive behavior suggests a magmatic connection exists between these volcanoes.

Additionally, this magmatic connection between Kīlauea and Mauna Loa results in a broad correlation between changes in their lava chemistry.

“For example, during the late 19th century when Mauna Loa 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 Mauna Loa.”

Long-term forecasting of volcanic activity currently relies upon extrapolation of a volcano’s past eruption record.

“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 Mauna Loa 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.