Mauna Loa is the largest shield volcano on Earth (above water, at least) active for at least the last 700,000 years, and scientific data indicates that future eruptions might be caused by volcanic activity.
Researchers in 2021 were able to model the flow of magma on the inside of the volcano while also determining what would and wouldn't be likely to trigger the next major eruption from Mauna Loa.
A large earthquake is in the column 'would be likely.' That conclusion is based on magma influx measurements made since 2014, driven by the topographic stress of the surrounding rock.
In a press release accompanying the 2021 study, Bhuvan Varugu, a geologist at the University of Miami's Rosenstiel School of Marine and Atmospheric Science, said she expects an earthquake of magnitude 6 or greater to relieve the stress caused by the influx of magma along a sub-horizontal fault beneath the western flank of the volcano.
"This earthquake might trigger an eruption."
Between 2014 and 2020, researchers determined that 0.11 square kilometers (about 0.04 square miles) of new magma flowed into a new location in the volcano chamber, changing direction as a result of the pressures exerted on it.
These kinds of magma body variations have never been measured before. Together with surface lava flows and ground shifts along the fault the volcano is sitting on, magma intrusions change the shape of the volcano and the likelihood of it erupting.
At Mauna Loa, volcanologists already understand that flank activity and eruptions are closely linked, so that changes in these flanks caused by magma injections can make a substantial difference in how the volcano behaves.
"A seismic event may be a game changer," said marine geologist Falk Amelung from the University of Miami.
"It would release gases from the magma comparable to shaking a soda bottle, generating additional pressure and buoyancy sufficient to break the rock above the magma."
Mauna Loa is already under a "extremely heavy" topographic load, according to the data.
Further magma intrusions will increase the likelihood of an earthquake or eruption, but it might not be required: Researchers suspect an earthquake may occur under the volcano's western flank.
Recent eruptions demonstrate how crucial an early warning is: lava from a Mauna Loa eruption reached the coast in only three hours in 1950; another major eruption in 1984 was preceded by substantial earthquakes.
With a large number of variables and estimates involved, predicting eruption timings is a difficult task, but careful magma mapping techniques like the one used in this new study can provide valuable data for future modeling.
"It's a fascinating issue," Amelung said.
"We can explain how and why the magma body changed over the previous six years. We will continue to monitor, and this will eventually lead to better models to predict the next eruption site."
Scientific Reports summarize the findings.
In May 2021, an earlier version of this article was published.