Mauna Loa Volcano Alert Level Raised to Yellow

The alert level at the Mana Loa Volcano on Hawaiʻi Island was raised from Green to Yellow today amid an increase in earthquakes and ground deformation rates, according to the Hawaiian Volcano Observatory.

The HVO says the rates exceed long term background levels and indicate “changes in the shallow magma storage system.”  The information was compiled by the HVO as a Volcano Observatory Notice for Aviation. The notice states that: “An eruption is not imminent and current rates are not cause for alarm.”

The HVO explains that there was a “significant earthquake swarm in October 2018,” with seismic stations recording 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 since then. “This compares to a rate of fewer than 20 per week in the first half of 2018.”

The HVO notes that shallow earthquakes are occurring in locations similar to those that preceded Mauna Loa’s most recent eruptions in 1975 and 1984.

“During this same time period, GPS instrumentation and satellite radar have measured ground deformation consistent with renewed recharge of the volcano’s shallow magma storage system. The current rate and pattern of ground deformation is similar to that measured during inflation of Mauna Loa in 2005 and again from 2014 – 2018,” according to the HVO.

“Together, these observations indicate the volcano is no longer at a background level of activity. Accordingly, HVO is elevating the Mauna Loa alert level to ADVISORY and the aviation color code to YELLOW.”

This increase in alert level does not mean that an eruption is imminent nor that progression to an eruption is certain. A similar increase in activity occurred between 2014 and 2018 and no eruption occurred.

According to the HVO, “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. 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. File April 2019. PC: US Geological Survey.