Categorized | Featured, Sci-Tech, Volcano

USGS raises Mauna Loa’s volcano alert level to Advisory status

USGS Hawaiian Volcano Observatory scientists are closely monitoring recent signs of unrest on Mauna Loa, the largest active volcano on Earth. In this 1985 aerial photo, Mauna Loa looms above Kīlauea Volcano’s summit caldera (left center) and nearly obscures Hualālai in the far distance (upper right). USGS photo.

USGS Hawaiian Volcano Observatory scientists are closely monitoring recent signs of unrest on Mauna Loa, the largest active volcano on Earth. In this 1985 aerial photo, Mauna Loa looms above Kīlauea Volcano’s summit caldera (left center) and nearly obscures Hualālai in the far distance (upper right). USGS photo.

MEDIA RELEASE

HAWAI‘I ISLAND, 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 have 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 (inflation) 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 (volcanoes.usgs.gov/activity/al…), 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 Hawai‘i County Civil Defense, the National Park Service and other emergency managers, as well as the public, if significant changes are detected.

TOP: Mauna Loa weekly earthquake rates between 2010 and September 17, 2015. Blue bars indicate the number of earthquakes that were located by the USGS Hawaiian Volcano Observatory seismic network. Earthquakes of all magnitudes are plotted. Subtle increases in earthquake rates started in mid-2013, while more obvious changes in rates started in 2014. BOTTOM: Change in distance across Mauna Loa's summit caldera between 2010 and September 17, 2015. Blue dots indicate the relative distance between two stations that span the summit caldera of Mauna Loa, shown in the map on the upper left. Sustained extension across the caldera started in mid-2014. This extension is one of the indicators of magma infilling a complex reservoir system beneath the summit and upper Southwest Rift Zone.

TOP: Mauna Loa weekly earthquake rates between 2010 and September 17, 2015. Blue bars indicate the number of earthquakes that were located by the USGS Hawaiian Volcano Observatory seismic network. Earthquakes of all magnitudes are plotted. Subtle increases in earthquake rates started in mid-2013, while more obvious changes in rates started in 2014.
BOTTOM: Change in distance across Mauna Loa’s summit caldera between 2010 and September 17, 2015. Blue dots indicate the relative distance between two stations that span the summit caldera of Mauna Loa, shown in the map on the upper left. Sustained extension across the caldera started in mid-2014. This extension is one of the indicators of magma infilling a complex reservoir system beneath the summit and upper Southwest Rift Zone.

In response to the status change, HVO is now posting weekly Mauna Loa updates on the HVO website (hvo.wr.usgs.gov/activity/mauna…). It is possible to receive these updates via email by signing up for HVO notices through the free USGS Volcano Notification Service (volcanoes.usgs.gov/vns/).

“The alert level change at Mauna Loa reminds us that it is an active volcano that will erupt again someday, so we should be prepared,” said Frank Trusdell, an HVO geologist who has extensively studied and mapped Mauna Loa. To facilitate public awareness and preparedness, HVO has posted on its website “Frequently Asked Questions about Mauna Loa” (hvo.wr.usgs.gov/maunaloa/FAQ_M…). Current monitoring data for Mauna Loa is also posted on the HVO website at hvo.wr.usgs.gov/maunaloa/curre….

For more information about Mauna Loa, other active Hawaiian volcanoes, and recent earthquakes in Hawaii, visit the HVO website (hvo.wr.usgs.gov) or email askHVO@usgs.gov

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