The U.S. Geological Survey this morning raised the alert level for Mauna Loa volcano from normal to advisory due to increased earthquake and ground deformation rates over the past few months.
An eruption is not imminent, the USGS Hawaiian Volcano Observatory said, and current conditions are no cause for alarm. Nor does it mean there is certain progression to an eruption for the Big Island volcano, scientists said.
However, the increase in both rates indicates changes in the shallow magma storage system at Mauna Loa, USGS said.
The USGS also changed the aviation color code from green to yellow, indicating that the volcano is exhibiting signs of elevated unrest above known background levels.
“Following a significant earthquake swarm in October 2018, HVO seismic stations have recorded an average of at least 50 shallow, small-magnitude earthquakes per week beneath Mauna Loa’s summit, upper Southwest Rift Zone, and upper west flank,” said the USGS. “This compares to a rate of fewer than 20 per week in the first half of 2018. Shallow earthquakes are occurring in locations similar to those that preceded Mauna Loa’s most recent eruptions in 1975 and 1984.”
USGS said during this same time period, GPS instruments and satellite radar measured ground deformation consistent with a renewed recharge of the volcano’s shallow magma storage system. The current rate and pattern of ground deformation is similar to that measured during the inflation of Mauna Loa in 2005, and again from 2014 to 2018.
The USGS noted that a similar increase in activity occurred between 2014 and 2018, however, when no eruption occurred.
“As has happened before, it is possible that current low-level unrest will continue and vary in intensity for many months, or even years without an eruption,” said the USGS. “It is also possible that the current unrest is an early precursor to an eventual eruption. At this time, we cannot determine which of these possibilities is more likely.”
Mauna Loa, which rises to an elevation of 13,681 feet, is the largest, active volcano on Earth. All communities on the flanks of Mauna Loa should be prepared, said USGS HVO, which remains in constant communication with Hawaii County Civil Defense.