On October 5th of 2022, the U.S. Geological Survey closed off the summit area of the Mauna
Loa volcano in Hawaii due to a swarm of shallow earthquakes.
A day later, the agency moved from weekly to daily volcano updates due to the changes
at this volcano.
It was later revealed that a new intrusion of magma at a depth of as little as 2 miles
or 3 kilometers was present underneath Mauna Loa's summit.
This input of shallow magma primarily occurred during the last 2 weeks of September, leading
to the volcano's most energetic earthquake swarm of the 21st century.
During this swarm, the number of daily volcanic earthquakes jumped from 16 to 30, and then
for a period of time, 50 quakes.
Although the number of earthquakes peaked between September 24th and September 30th,
the quakes after the fact slowly declined to near background levels by October 23rd.
However, since then the number of earthquakes has once again increased, nearly matching
the level of seismicity measured in late September.
So, what does all of this mean?
As a brief answer, the Mauna Loa volcano is undergoing a phase of very heightened activity
where it could theoretically erupt with as little as 60 minutes warning, potentially
even a bit less.
Although an eruption does not appear imminent as of the writing of this video, and most
magmatic intrusions do not result in an eruption, the last 45 days of activity at this volcano
have represented the most activity at Mauna Loa since its last eruption ended in 1984.
For context, Mauna Loa is the 2nd tallest active volcano on the Big Island of Hawaii
and exists due to the underlying Hawaiian Hotspot.
Mauna Loa covers 51% of the landmass of the Big Island, as shown here.
This volcano is currently undergoing its longest period without an eruption in the last 200
years, as it has not erupted since 1984 and in the last 3,000 has erupted about once every
6 years.
And, since early July of 2019 Mauna Loa has been at a yellow alert level due to persistent
volcanic activity including earthquakes and ground deformation, as intruding magma has
pushed overlying rock upwards.
The elevated levels of ground uplift may seem relatively small as since August of 2022 Mauna
Loa's summit has been uplifted by a mere 1.1 inches or 2.8 centimeters.
In terms of volcanoes, this is quite significant, as it surpasses the rate of uplift at two
other volcanoes in the United States with known ongoing magmatic intrusions.
However, the uplift rate is still a bit low for me to suggest a high probability of eruption
in the short term future.
For comparison, before Fagradalsfjall's August 2022 eruption, the ground was uplifted by
a maximum of 2 centimeters or four fifths of an inch in only 6 days.
I know that the people who live on the Big Island do not like this level of uncertainty,
but due to the nature of the current science of volcanology we are unable to give long
term forecasts of a volcano.
In the event an eruption does occur, it could either remain within Mauna Loa's summit caldera,
or it could create a lava flow that travels down one of four slopes.
If such an eruption traveled down Mauna Loa's southwestern rift zone and headed towards
the west, there would be essentially nothing that could be done to stop a lava flow as
they often reach the ocean within hours.
Towards the northwest or towards the southeast, a primitive lava barrier could be built as
lava flows takes on the order of days to weeks to reach populated areas.
On the other hand, if lava flows headed east-northeast towards Hilo there would be a decent amount
of time to attempt to divert the lava flow as it often takes on the order of weeks but
more typically months to reach populated areas in that direction.
As a final note, although there are two clusters of earthquakes around the summit of Mauna
Loa, only one of the two is directly linked to in part magmatic activity.
The cluster to the west does not represent a magmatic intrusion but rather is a location
where stress from uplifting and stretching crust due to magmatic dike intrusion and rift
zone extension is released.
Thanks for watching!
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