Hawaii’s Kilauea volcano has wreaked havoc on the landscape since it started erupting through new fissures on May 3, and it doesn’t show signs of stopping. Of the five volcanoes on the Big Island of Hawaii, Kilauea is considered the most active, so its activity is perhaps not surprising. Coming in second is Mauna Loa, Kilauea’s relatively huge but dormant neighbor 22 miles away. The relationship between their eruptions is not fully understood, but in 2012, Rice University scientists showed that they are indeed physically linked.
Kilauea and Mauna Loa have a complicated relationship. Sometimes it seems that they “inflate” — fill with magma — nearly simultaneously, while other times their activity alternates. In their Nature Geoscience paper, published in 2012, the Rice University scientists dug into the history of the volcanoes to devise their theory, which covers both seemingly opposing trends.
Kilauea (marked in red) is tiny compared to Mauna Loa (to its left, in green).
Technically, Kilauea has been erupting gently since January 1983 — recently it started doing so much more furiously — and Mauna Loa hasn’t erupted since March 1984, an event that lasted three weeks. Those dates may seem worryingly close, but the former eruption didn’t have any discernible effect on the latter. On an even longer timescale, the relationship between their eruptions appears even less predictable: While Kilauea lay dormant between 1934 and 1952, Mauna Loa became quite active, erupting four times; meanwhile, while Mauna Loa was dormant between 1952 and 1974, Kilauea had at least 28 eruptions. If it sounds confusing, that’s because it is, but the team’s theory seems to explain both.
In the paper, they presented evidence that the volcanoes were connected, and that this connection could help explain both their simultaneous and “lagging” inflation. Previously, scientists had already established that the volcanoes both draw magma from different sections of the same “hot spot” on the Earth’s mantle. Key to the study is that the volcanoes draw this fluid out via the asthenosphere, the uppermost, half-molten layer of the Earth’s mantle, 50 miles below the surface. This connection, they write, is the root of the volcanoes’ shared activity. If magma rises due to increased pressure in the asthenosphere, the team hypothesize, it will feed into both Kilauea and Mauna Loa, causing simultaneous inflation.
Kilauea and Mauna Loa are connected via the asthenosphere, the uppermost layer of the Earth's mantle.
But, as we have seen, sometimes inflation in one volcano lags behind the other. That, the team says, is due to eruptions, which can cause a sharp decrease in pressure in the erupting volcano and therefore decreased inflation. Meanwhile, as the rising asthenosphere forces magma upward, the other, not-erupting volcano continues to fill.
Lava flow from Kilauea is ultimately linked to magma rising in the asthenosphere, from which Mauna Loa also draws its magma from.
“Although an increase in the asthenospheric magma supply can cause simultaneous inflation of Kīlauea and Mauna Loa, we find that eruptive activity at one volcano may inhibit eruptions of the adjacent volcano, if there is no concurrent increase in magma supply,” the authors write. In other words, an eruption in one volcano seems to act as a pressure release valve for the other, leading it to experience a period of relative dormancy.
This is, of course, just a theory, and experts have yet to apply it to Kilauea’s ongoing explosion. There haven’t been any warnings issued by the United States Geological Survey for Mauna Loa since Kilauea started erupting. The most recent was issued on April 26, the week before the eruption; that yellow-level advisory reported small earthquakes and “slowing deformation related to inflation of a magma reservoir.”