Volcanic mystery solved: Mauna Loa and Kīlauea are connected 25 miles under Pāhala

 One deep mystery about our Hawai’i volcanoes has been solved.

The mystery was this: Do Mauna Loa and Kīlauea have independent connections to the hot rock in the Earth’s mantle, or do they share a magma reservoir nearer the surface.

Now, we know it’s the latter.

That’s due to a detailed study, reported in the December 22, 2022, issue of the journal Science. The study used artificial intelligence/machine learning to make sense of 3-D imagery of the locations of nearly 200,000 recent earthquakes under Mauna Loa and Kīlauea.

The study is entitled “The magmatic web beneath Hawai‘i.” It was written by John D.Wilding, Weiquiang Zhu, Zachary Ross and Jennifer Jackson. 

All of Hawai’i’s volcanoes are ultimately fed from the planet’s mantle, which is hundreds to a couple of thousand miles below the surface. They are fed by a phenomenon that has been called a Hot Spot, which drives molten rock from the deep mantle through cracks in the Earth’s crust, eventually to the surface.

The seismic study found that there is a magma storage area about 25 miles down, roughly under the Hawai’i Island town of Pāhala.

It takes the form of a series of horizontal structures, like stacked plates. These plates are roughly 3-4 miles wide, 1,000 feet thick, and vertically separated by about 1,500 feet of rock. The researchers call it the Pāhala sill complex.

From there, independent channels lead to the summit of Mauna Loa and the top of Kīlauea. The Mauna Loa channel is comparatively direct, while the Kīlauea channel goes laterally for a while, then rises to what looks like a secondary magma storage area 6-9 miles under the Kīlauea summit.

These channels are identified in the research as “seismicity bands,” which are areas, when mapped in 3-D, that show the location of pathways where magma may be moving.

So, yes, it looks like the two volcanoes are connected. But the magma feeding the two of them comes from different parts of the Pāhala sill complex, far enough apart that they sometimes seem to act independently.

So what about the newest Hawaiian volcano, Kama’ehuakanaloa (formerly Lō’ihi)? It does not seem to share the Pāhala sill complex, and appears to have its own route from the mantle, the authors write.

Star-Advertiser reporter Timothy Hurley’s review of the study here. 

National Geographic’s report on the study is here. 

© Jan TenBruggencate 2022