On January 14th, 2022 at 4:20 am local time, a new explosive eruption began at the Hunga
Tonga-Hunga Ha'apai volcano in the nation of Tonga.
As many of the volcano's vents are either below or just above sea level, magma interacted
with the seawater, causing it to flash to steam and explode.
This series of explosions created a towering eruption plume which rose to a height of 16,800
meters or 55,000 feet into the atmosphere.
The plume had a primarily white color, hinting that the main constituent of the cloud was
water vapor.
However, at lower elevations of up to 11,000 feet, a distinguishable cloud of ash was also
ejected, along with significant amount of sulfur dioxide gas.
This sulfur dioxide gas soon descended on the island of Tongatapu, causing a distinct
odor.
Then, many residents noted a secondary effect of the eruption.
The ocean water was seemingly at high tide when it was not supposed to be, and the water
was flowing in an unusual manner.
Unknown to these residents, what they were witnessing was a small scale tsunami.
Instruments recorded a more than an hour long peak correlating with a 30 centimeter or 12
inch high tsunami.
While it is unknown exactly what caused this tsunami, here are my thoughts.
I did the math, and the observed small tsunami was likely generated when an area of approximately
50 million cubic meters of rock slid into the ocean over the span of several seconds.
For comparison, the theorized landslide is similar in size to the 2010 landslide at the
Mount Meager volcano in Canada.
This large landslide could have either occurred on the island or at one of its submarine vents,
such as adjacent to the 1988 eruption vent.
While this tsunami is confirmed, its direct cause is not.
It could have for example been instead generated by harmonic tremor loosening already weakened
rock unrelated to the volcano on the seafloor.
In the event it originated on the island of Hunga Tonga Hunga Ha'apai, there should be
a large "c" shaped crater on the island which will become visible once the ash column clears.
While the tsunami was nondestructive, the mere fact that it occurred is worrying.
Volcano edifice collapses are typically very difficult to predict, especially at small
volcanic islands.
A similar larger volume volcanic tsunami occurred in 2018 at Anak Krakatoa, which generated
waves up to 25 meters in height and devastated the local coastline.
A second example is the Ritter Island volcano which produced a large tsunami in 1888.
While I do not personally expect an even larger tsunami to occur, I do recommend that several
buoys be placed within 10 kilometers of the volcano.
This would give advanced warning in the unlikely event another larger tsunami was to occur.
Today's eruption was most definitely a surprise as Hunga Tonga had produced a very recent
eruption which began on December 20th and ended on January 1st.
This prior surtseyan eruption created intermittent plumes of ash and ejected bombs of lava alongside
generating small pyroclastic flows.
All of this activity during a 13 day period expanded the landmass of the volcano by 72%
via a new volcanic vent.
After January 1st, volcanic tremor at Hunga Tonga stopped, and the emission of volcanic
gasses returned to normal levels.
Then, on January 4th, a magnitude 5.0 earthquake hit to the west of the volcano.
It occurred deep in the upper mantle, but seemingly had a volcanic signature to it despite
its distance from the island.
A week later on January 11th, a second earthquake which was much shallower occurred and had
a similar signature, rating in as a magnitude 4.9.
While minor, these earthquakes can now be reinterpreted as signaling the intrusion of
a second batch of magma into the Hunga Tonga Hunga Ha'apai volcano.
Over the next 3 to 15 days, more explosions will occur as surtseyan style activity creates
black and white colored plumes of ash and further expands the island.
If you are an airline pilot, I recommend avoiding the region marked on screen until this brand
new eruption ends.
Thanks for watching.
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