September 2015 – HAWAII – Scientists at the U.S. Geological Survey Hawaiian Volcano Observatory have elevated the Volcano Alert Level for Mauna Loa from normal to advisory. This change in status indicates that the volcano is showing signs of unrest that are above known background levels, but it does not mean that a Mauna Loa eruption is imminent or certain.
HVO’s seismic stations recorded elevated rates of shallow, small-magnitude earthquakes beneath the summit, upper Southwest Rift Zone, and west flank of Mauna Loa for at least the past year. During this same time, HVO monitoring instruments have measured ground deformation on Mauna Loa that is consistent with recharge of the volcano’s shallow magma storage system. Together, these observations indicate that Mauna Loa is no longer at a background level of activity.
Based on these changes in activity, and in accordance with the USGS Volcanic Activity Alert-Notification System, HVO raised the Volcano Alert Level for Mauna Loa to advisory and the Aviation Color Code to yellow. The Volcano Alert Level is a four-tiered system that uses the terms Normal (background levels), Advisory, Watch, and Warning (highest threat) to inform the public about a volcano’s status. These alert levels are issued in conjunction with Aviation Color Codes, which provide information about volcanic-ash hazards to the aviation industry. The codes are Green (background), Yellow, Orange, and Red (eruption imminent).
An advisory/yellow status is declared when one or more volcano monitoring parameters are above the background range of activity, which is the current situation on Mauna Loa. Progression toward an eruption is by no means certain, but the volcano is closely watched to track how the unrest develops. “It’s possible that the increased level of activity at Mauna Loa could continue for many months, or years, without leading to an eruption,” said Tina Neal, HVO’s Scientist-in-Charge. “It is also possible that the current unrest could be a precursor to the next eruption of Mauna Loa. But at this early stage, we cannot determine precisely which possibility is more likely.”
HVO previously maintained an advisory/yellow status for Mauna Loa following increased rates of ground deformation during the rapid inflation of the volcano in 2004-2005. That period of inflation, similar to deformation currently observed, did not result in an eruption. When the inflation slowed to background levels in early 2010, the status of Mauna Loa was returned to normal/green. The most recent eruption of Mauna Loa, which began on March 25, 1984, and lasted just over three weeks, was preceded by up to three years of increased earthquake activity. But, in contrast to pre-1984 activity, the energy released by recent earthquakes remains comparatively low. HVO continues to closely monitor Mauna Loa, and will notify Hawaii’s County Civil Defense, the National Park Service and other emergency managers, as well as the public, if significant changes are detected. –KITV