Research conducted by a University of Miami scientist and his graduate assistant accurately predicted which of the two rift zones of Hawaii’s Mauna Loa volcano would erupt.
The Mauna Loa, the world’s largest active volcano, began erupting on Nov. 27 for the first time in nearly 40 years, spewing lava 100 feet to 200 feet into the air.
Using a satellite-based technique called interferometric synthetic aperture radar (InSAR) to measure surface displacements and to estimate how much magma was accumulating under the volcano during a six-year period (2014-2020), the two researchers proposed last year that the next movement of magma would be upwards into the volcano’s summit and then northward, opening fissures in Mauna Loa’s northeast rift zone.
"And that’s exactly what happened. We predicted it,” said Falk Amelung, a professor of marine geosciences at the University’s Rosenstiel School of Marine, Atmospheric, and Earth Science, who once lived on Oahu, part of the Hawaiian island chain, and has studied Mauna Loa extensively. "This represents years of hard work and intensive research paying off and shows that the precise evaluation of stress changes can be a powerful tool for informed forecasts of future activity.”
Amelung and research assistant Bhuvan Varugu published their research in Scientific Reports, a peer-reviewed open-access journal published by Nature Portfolio. The study outlined a couple of possible scenarios, including one where " continuing pressurization of the magma body leads to upward and northward injection of a dike and possibly propagation to the surface.”
When Amelung learned of the eruption, "I was terribly worried that the dike would spread southward because of the lava flow hazards. But once it became clear that the dike had propagated to the north, I was relieved to know that no one would be in harm’s way and that the many years of our hard work and research had produced accurate results.”
Late last week, lava flows from the Mauna Loa eruption were moving toward a main highway. And an update issued on Dec. 1 by the U.S. Geological Survey confirmed that the lava flows "are traveling to the north toward the Daniel K. Inouye Highway (Saddle Road) but have reached relatively flatter ground and have slowed down significantly as expected.”
At the time Amelung and Varugu initiated their Mauna Loa study nearly seven years ago, data from synthetic aperture radar (SAR) satellites was not easy to acquire, making it a challenge for the scientists to get a complete picture of the volcano’s ground movements, according to Amelung.
To clear that hurdle, Amelung helped create the Geohazard Supersites and Natural Laboratory, an international partnership of NASA and five other space agencies that pool their satellite resources to make SAR data of geohazard sites more readily available to the scientific community. For their Mauna Loa study, the two researchers used data supplied by the Italian Space Agency. "Now, we can do complex geohazard assessments of volcanic sites within a few hours,” Amelung said. "It’s a splendid example of scientific progress.”
When Amelung lived on Oahu, he would visit the big island of Hawaii every few months to study Mauna Loa, hiking up to its summit several times.
"It is fascinating because it is so big,” he said. "It’s a natural laboratory to understand earthquake-volcano interactions. But it’s important to remember that it is hazardous. This time, we seem to have been lucky as far as the eruption not causing much damage. An eruption in the south would have reached populated areas within hours.”
Amelung and Varugu responded to questions to explain their research and the nature of volcanic eruptions in greater detail.
Detail the exact nature of your Mauna Loa study and how it predicted the location of this latest eruption.
Varugu: As magma recharges under a volcano, it often exhibits ground deformation at the surface. We derived the ground deformation on Mauna Loa volcano from satellite images over six years (2014-2020) and mathematically inverted it to infer the magma body’s location, shape, and growth. We studied the factors affecting the magma growth as it reaches the shallow level under the volcano and as stress accumulated due to magma pressurization. In 2015 the area of magma accumulation moved southward but there was no eruption, and then it returned to the original location. Overall, from six years of magma pressurization, we identified significant stress accumulation in the upward and northward of the shallow magma body and determined them as future directions of magma growth. The magma recharge continued ever since (2014 to 2022), and the current eruption occurred as the magma first moved upward into the summit and then north, opening fissures into the northeast rift zone of the volcano. So, our study helped identify zones of stress accumulation that can be potential future eruption zones.
What early signs, such as increased earthquake activity, indicated that the Mauna Loa was going to erupt?
Amelung: In August and September, the number of shallow earthquakes as well as the rate of inflation increased by a factor of about three.
Could we potentially see a large earthquake result from this eruption?
Amelung: Yes. Hawaiian volcanoes have horizontal décollement faults under the flanks which occasionally rupture in large earthquakes. This eruption started with the intrusion of a blade-like magma body into the volcanic edifice known as a dike. This dike loaded the fault under the eastern flank. However, inflation in the prior 20 years primarily loaded the fault under the western flank. Unfortunately, we don’t know at what threshold stress the fault will rupture. A significant earthquake, magnitude 6 or greater, can occur at any time. But it may also require additional loading after the eruption by new magma intrusion.
What’s unique about the Mauna Loa?
Varugu: Mauna Loa is the largest subaerial volcano on Earth and has had a rich eruption history, approximately 33 times in the past 200 years. Its mammoth size is an indication of historic lava flows. And it is fascinating that many eruptions at Mauna Loa have been preceded or succeeded by an earthquake. So, a strong correlation exists between earthquakes and eruptions there.
How are volcanic eruptions and earthquakes linked? Can earthquakes trigger volcanic eruptions and can volcanic eruptions trigger earthquakes?
Amelung: Every eruption is associated with volcano-tectonic seismicity, but these small earthquakes represent the breakage of the rock in response to ascending magma. They are different from tectonic earthquakes that occur on tectonic faults. If there is a tectonic fault near an active volcano, it might be triggered. There are two possible triggering mechanisms. The first is the removal of magma from the magma reservoir that unclamps the fault. The second is magma intrusions into the volcanic edifice that can load the fault. This second mechanism is at work at Mauna Loa.