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Several months of small earthquakes and signs of magma movement underground at Mauna Loa prompted scientists Tuesday to raise the alert level by a notch for the massive volcano.
They stressed that there is no cause for alarm as the alert moved from “normal” to “advisory,” which indicates signs of unrest above background levels at the volcano, which last erupted in 1984.
“It’s really important to emphasize that nothing is imminent and people should not be alarmed,” said Tina Neal, scientist in charge at the Hawaiian Volcano Observatory.
Mauna Loa, the largest active volcano on earth, reaches 13,681 feet. The alert is a way to warn people that activity has been percolating and they should remain aware and consider how to prepare in case things escalate. Scientists said they can’t predict whether the situation will settle down or trend upward.
Similar rumblings from 2015 to 2018 led to “advisory”-level warnings for Mauna Loa that were later lifted.
“It’s very similar to what we saw in 2015 and 2018, and that time, of course, it did not end in eruption,” Neal said. “We could be in another period like that, where we see slightly elevated earthquakes for a while and they go back down.”
Meanwhile, Kilauea Volcano has been quiet and stable after the spectacular eruption along its East Rift Zone last year, and its alert level is normal.
After the “advisory” level, there are two higher levels of alert: a “watch,” which indicates heightened unrest with higher potential for eruption, and a “warning,” which means a hazardous eruption is suspected, imminent or underway.
“We’ve been actually watching this for a number of months now and waiting to see if the trend of slightly elevated earthquakes and rates of ground motion continues,” Neal said. “We wanted to see if it was going to be a persistent pattern or go back to quiet levels.”
“There are clear signs that the shallow magma system is accumulating molten material,” she added. “Our GPS instruments are showing the upper part of the volcano is inflating. The distance across the summit caldera is lengthening just a little bit.”
After a swarm of earthquakes in October, seismic stations have recorded more than 50 small earthquakes per week beneath Mauna Loa’s summit, upper Southwest Rift Zone and upper west flank, according to the U.S. Geological Survey. That compares with 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 in its announcement Tuesday.
The largest recent quake registered magnitude 3.1 on June 21, Neal said.
The current unrest could continue for months or years with no eruption, or it could intensify over time.
“We would expect to see quite a few more earthquakes and larger earthquakes and more ground swelling before an eruption,” Neal said. “We’re confident that we’ll see some warning. It may not be great. We are hoping to see days to weeks of warning. It may be hours or days.”
The USGS also shifted the aviation color code, which warns of airborne ash hazards, from green to yellow, indicating activity above background levels.
The observatory advised communities on the flanks of the volcano to be prepared.
“Be aware and know what you would do in case things get more serious and the forecast goes out for an eruption,” Neal said. “The good thing is that preparing for a volcanic eruption has a lot of similarities to preparing for an earthquake or tsunami. It’s a good time to think about emergency supplies and your family plan.”
STAY INFORMED ONLINE
Officials encourage residents to stay informed by following updates for Mauna Loa online at the Hawaiian Volcano Observatory or signing up for email notifications via the Volcano Notification Service online at volcanoes.usgs.gov/vns. To register for Civil Defense notifications, visit hawaiicounty.gov/civil-defense.
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