Is Hawaii’s Mauna Loa, the world’s largest active volcano, in danger of erupting?

A series of earthquakes continues to shake beneath Hawaii’s Mauna Loa, the world’s largest active volcano, leaving geologists to continue to warn it is in a “state of heightened unrest”.

A 5.0 magnitude earthquake was the strongest ripple to tear through the belly of the formation, which is located in the center of the Big Island of Hawaii.

News of increased seismic activity in October prompted the National Park Service to close access to the summit to climbers and tourists, a move the agency said was “a precautionary measure.”

On Thursday, Oct. 27, the Hawaii Emergency Management Agency issued its first press release on the Mauna Loa unrest, noting that while seismic activity is of concern to residents, there are currently “no signs that an eruption is imminent”.

“We remind people to take this opportunity to sign up for county emergency alert messages and prepare or review their plans to be prepared for any disaster,” said County Civil Defense Administrator Talmadge Magno. ‘Hawaii.

The civil defense agency has also held meetings across the island in an effort to educate residents on how to prepare for a possible emergency over the past few weeks, which includes recommendations such as equipment from their homes with a “go” bag with food.

“Not to freak everyone out, but they need to be aware that you live on the slopes of Mauna Loa. There is potential for some sort of lava disaster,” added Magno, who noted that the volcano makes up 51% of the island’s landmass.

Although the volcano hasn’t erupted since 1984, the past few weeks of increased subterranean earthquakes have raised local concerns that Mauna Loa may be due to an overflow.

Here, we detail everything we know about the possibility of such an outcome and why Mauna Loa has been on the radar of scientists and geologists for the past few weeks.

What is Mauna Loa?

Besides Mauna Loa, the Big Island of Hawaii is made up of four major volcanoes: Kilauea, Mauna Kea, Hualalai and Kohala. The aforementioned volcano is by far the largest of the group and also holds the record among active volcanoes on the planet for being the largest. Mauna Loa – aptly named “Long Mountain” – extends 13,679 feet into the air above sea level where it covers half the length of the island at 60 miles long and 30 miles wide . The summit caldera, called Mokuaweoweo, is itself 3 miles long.

When did Mauna Loa last erupt?

The sky-scraping formation has been relatively quiet for the past few decades, as scientists celebrated the 30th anniversary of its last eruption on March 25, 2014. Although the last one was in 1984, Mauna Loa eruptions have been happening since generations; since 1832, there have been 39 documented eruptions while the USGS estimates an average of one has occurred every six years over the past 3,000 years.

Lava fountain on Mauna Loa, March 26, 1984 (USGS/JD Griggs)

Lava fountain on Mauna Loa, March 26, 1984 (USGS/JD Griggs)

When did the new activity start?

Warnings began to be issued in mid-September when geologists began recording a slight increase in the number of earthquakes shaking beneath its surface. For a typical day in mid-September, the site experienced about 20 earthquakes per day, but that number rose to 40 in early October.

In response to this shift in seismic activity, the US Geological Survey Hawaiian Volcano Observatory updated its advisory level from green to yellow as a precaution for “increased unrest” at the volcano.

(In this four-level advisory system, green is the lowest and equates to normal activity; yellow indicates the “volcano is showing signs of elevated unrest above known background activity”; orange is a watch and means there is “escalating unrest with potential increase in eruption”; and red means an eruption is “imminent, ongoing, or suspected”.)

In October, Mauna Loa’s summit was closed to tourists due to increased activity in what the NPS called “a precautionary measure.”

Does it burst now – or will it burst soon?

Scientists and geologists who closely monitor activity at Mauna Loa note that there is no eruption and add that currently there are no signs of an impending eruption.

“However, Mauna Loa continues to be in a state of heightened unrest, as indicated by increased seismic activity and summit inflation,” the USGS Hawaiian Volcano Observatory wrote in its update. October 27 daily.

Scientists note that the rate of earthquakes occurring at Mauna Loa is not sufficient to warrant raising the alarm higher than the current volcanic alert level advisory of yellow.

By comparison, before the 1975 eruption at the site, earthquakes exceeded 1,000 per day, while during the last eruption in 1984 scientists recorded hundreds per day in the weeks before its final blow. .

(The USGS last issued a yellow alert for Mauna Loa in 2019.)

The scene of Kilauea, a volcano near Mauna Loa (Getty Images)

The scene of Kilauea, a volcano near Mauna Loa (Getty Images)

What causes increased seismic activity?

USGS Hawaiian Volcano Observatory geologists explained in an update provided Oct. 16 that the cause of the increased activity is a “renewed supply of magma” to the volcano’s reservoir system, which is described by the USGS as the region below the vent of a volcano where molten rock (magma) is stored before eruption. Also known as a magma storage area or magma reservoir.

“As the reservoir expands, it triggers small earthquakes directly below the Mokuaweoweo caldera and in an area just northwest of the caldera,” the agency said in Sunday’s update.

“The current locations of earthquakes and deformations do not necessarily mean that the next eruption will occur there. Mauna Loa remains at a high alert level of ADVISORY/YELLOW,” the statement added, noting that the Current activity “does not suggest that progress towards an eruption is certain, and there is no indication that an eruption is imminent.”

Some of the signals that experts rely on to provide them with these estimates are the earthquakes themselves, in addition to satellite imagery, temperature data and visual observation.

For example, one such device that measures important visual elements are inclinometers, which are installed to measure the tilt on the ground surface of a volcano.

Does this pose a risk to Hawaii residents?

Mauna Loa is a very active volcano and because of this, it has remained the top priority for the USGS to closely monitor its activity. Since 1868, it has produced large quantities of basalt – which is very fluid and dark lava – which has reached ocean shores eight times. When it last erupted in 1984, its molten flow occurred within 7.2 km of Hilo, the island’s largest urban center with about 44,000 residents.

Geologists and scientists are however monitoring the situation closely and in their latest update indicated that at this time “Mauna Loa is not erupting and there are no signs of an eruption. imminent at the moment”.

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