Water isn’t the only liquid in the Solar System. As we mentioned Tuesday, we were deeply amused to find that Io, with its lava reservoirs, was listed as an ocean world. In a way, this kind of means Earth has both surface oceans of water and sub-surface seas of magma.

And that magma likes to escape. Back in July 2018, residents of the Big Island of Hawaii were sent fleeing from their homes, as the Kīlauea volcano split open subdivisions and casually oozed lava over everything. This particular volcano is one of the more active and most studied in the world, but it still has a lot of surprises to offer.  This eruption was the stuff researchers dreamed of, and then graduate student Penny Wieser flew halfway around the world to take advantage of all the volcano was offering.

Using samples of minerals formed during the eruption, she and her team worked to understand where in the Earth this molten rock originated. In our standard textbook diagram of a volcano, a single magma chamber feeds eruptions. Kīlauea, however, breaks the mold and actually has a shallow reservoir 0.5-2 kilometers beneath its eastern rim, and another 3-5 kilometers deep reservoir to the south. Each reservoir has a different composition reflecting the amount of gas at that depth and the different mixes of chemicals. 

Early measurements that looked at gases trapped in volcanic glasses had thought the 2018 eruption came from the shallow reservoir, but Wieser went the extra step of also studying the olivine crystals that formed in the fresh lava. She notes there are structures that looked like they came from the deep reservoir that was responsible for eruptions in the 1960s and 1970s, hinting that the 2018 eruption also came from deeper down. In December 2020, another eruption, this time from the shallow reservoir, occurred, and like so many familiar eruptions, simply fountained and beautifully oozed. This raises the question, “Was the lower reservoir responsible for the home-destroying habits of the 2018 eruption?” Only time and more eruptions will tell, but with each new measurement, we get better at linking chemistry, structure, and severity of the outcome.

More Information

Eos article

“Reconstructing Magma Storage Depths for the 2018 Kı̄lauean Eruption From Melt Inclusion CO2 Contents: The Importance of Vapor Bubbles,” Penny E. Wieser et al., 2020 December 14, Geochemistry, Geophysics, Geosystems