Hawaii’s Active Volcanoes are a Couple Fed by Same Source

Mauna Loa and Kilauea are Earth's largest and active volcanoes and they are located at a distance of 22 miles apart in the Hawaii Volcanoes National Park on the island of Hawaii. These two are the most studied and best instrumented volcanoes and have been under continuous observation by scientist at USGS's Hawaiian Volcano Observatory (HVO) since 1912.  Kilauea has erupted 48 times on HVO's watch, with a nearly continuous flank eruption since 1983. Mauna Loa has erupted 12 times in the same period, most recently in 1984.

But not much was known about the enigmatic behavior of these two volcanoes.

The study conducted by scientists at Rice University, the University of Hawaii, the U.S. Geological Survey (USGS) and the Carnegie Institution of Washington is the first one to offer a plausible model that explains eruptive patterns at Mauna Loa and Kilauea.

A link in Earth's upper mantle could account for Kilauea and Mauna Loa's competition for the same deep magma supply and their simultaneous "inflation," or bulging upward, during the past decade.

The eruptive patterns are that when one is active the other is quiet. The GPS records showed that each bulged notably due to the pressure of rising magma.

"We know both volcanoes are fed by the same hot spot, and over the past decade we've observed simultaneous inflation, which we interpret to be the consequence of increased pressure of the magma source that feeds them," said lead author Helge Gonnermann, assistant professor of Earth science at Rice University. "We also know there are subtle chemical differences in the lava that each erupts, which means each has its own plumbing that draws magma from different locations of this deep source.

"In the GPS records, we first see inflation at Kilauea and then about a half a year later at Mauna Loa," he said. "Our hypothesis is that the pressure is transmitted slowly through a partially molten and thereby porous region of the asthenosphere, which would account for the simultaneous inflation and the lag time in inflation. Because changes in pore pressure are transmitted between both volcanoes at a faster rate than the rate of magma flow within the porous region, this can also explain how both volcanoes are dynamically coupled, while being supplied by different parts of the same source region."

According to Gonnermann, the transmission of pressure through the permeable rock in the asthenosphere is akin to the processes that cause water and oil to flow through permeable layers of rock in shallower regions of Earth's crust.

"When we fitted the deformation, which tells us how much a volcano inflates and deflates, and the lava eruption rate at Kilauea, we found that our model could simultaneously match the deformation signal recorded over on Mauna Loa," said James Foster, co-author and assistant researcher at the University of Hawaii School of Ocean and Earth Science and Technology. "The model also required an increase in the magma supply rate to the deep system that matched very nicely with our interpretations and the increased magma supply suggested by the jump in CO2 emissions that occurred in late 2003."

"To continue this research, we submitted a proposal to the National Science Foundation (NSF) earlier this summer to extend our study back in time to cover the last 50 years," Foster said. "We plan to refine the model to include further details of the magma transport within each volcano and also explore how some known prehistoric events and some hypothetical events at one volcano might impact the other. This work should help improve our understanding of volcanic activity of each volcano."

But seems like the Earth scientists disagree about the potential links between adjacent volcanoes. Gonnermann hopes that the new model could be useful in studying other volcanoes like those in Iceland or the Galapagos Islands.

"At this point it is unclear whether Hawaii is unique or whether similar volcano coupling may exist at other locations," Gonnermann said. "Given time and ongoing advances in volcano monitoring, we can test if similar coupling between adjacent volcanoes exists elsewhere."