USGS Volcano Alert Level for Mauna Loa elevated from ‘normal’ to ‘advisory’ status.
More than 31 years after Mauna Loa last erupted, sending lava within 4.5 miles of Hilo, the largest active volcano in the world is showing signs of unrest.
Scientists at the U.S. Geological Survey Hawaiian Volcano Observatory Thursday elevated the Volcano Alert Level for Mauna Loa from “normal” to “advisory.” There are four levels of alerts: “normal” — or background level, “advisory,” “watch,” and “warning” to inform the public about a volcano’s status.
The change in status indicates the volcano is showing signs of unrest that are above known background levels, but it does not mean an eruption is imminent or certain, officials said.
Normally, Mauna Loa sees up to 10 earthquakes per week, and recently that has escalated to 40 earthquakes per week. Prior to eruptions in 1975 and 1984, about 100 earthquakes were recorded each day.
“We expect the seismicity to grow steadily and be more consistent and persistent, and even the rates to change before we forecast an eruption,” predicted Frank Trusdell, an HVO geologist who has studied Mauna Loa extensively and was present for its last eruption in 1984.
The mountain saw a period from 2004-05 until 2009 when the volcano remained in a state of inflation, but did not erupt. When the inflation slowed to background levels in early 2010, the status of Mauna Loa was returned to “normal.”
“Mauna Loa is not a dead volcano, it is still active,” said Trusdell. “People should take the time to understand the hazards from Mauna Loa and what they present, and people should know an eruption is not imminent and HVO is monitoring it, and if there is any change that we will alert the emergency managers and notify the public.”
Since mid-2014, monitoring instruments have measured inflation on Mauna Loa consistent with recharge of the volcano’s shallow magma storage system, as well as elevated rates of shallow earthquakes of less than 2.5-magnitude beneath the summit, upper Southwest Rift Zone and west flank, Trusdell said.
Asta Miklius, a geophysicist who manages the observatory’s deformation monitoring network, said the current bout of inflation appears to be occurring under Mauna Loa’s summit and upper Southwest Rift Zone. The volcano’s magma storage system, estimated to be about 2 miles beneath the surface, consists of two reservoirs, a spherical-shaped reservoir near the southeast wall of the caldera and a tabular reservoir, which runs the length of the caldera toward the upper Southwest Rift Zone.
Trusdell said scientists expect to see earthquake counts pick up “so that we are looking at hundreds of earthquakes per day,” with increased inflation, volcanic tremors and earthquake swarms before Mauna Loa enters its next eruption phase.
“As we get closer, we will see characteristic signatures of volcanic tremor and earthquake swarms — those both say that the molten material is migrating,” he explained. “At that point, when the earthquakes start building to hundreds per day, we will issue press releases and let emergency managers know that Mauna Loa looks like it’s starting to get closer to an eruption. Then, when we see more seismic signatures, we would forecast an eruption would be imminent and to expect the summit phase to commence.”
“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, in a prepared statement. “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.”
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June 12 , 2016. Mauna Loa , Hawai :
Source : westhawaiitoday. HVO.