On January 15th, 2022, the Hunga-Honga Hunga Ha'apai volcano in the nation of Tonga exploded
with a force equivalent to the detonation of 6 million tons of tnt.
This released a powerful shockwave and caused a large landslide to occur, generating a tsunami
wave of up to 15 meters or 49 feet in height.
What made this eruption so unique was that in the last 35 years, scientists have been
able to predict almost every single large volume explosive eruption.
The work of geologists saved many lives for example during the Mount Pinatubo eruption
in 1991, by correctly interpreting the magnitude of the imminent event.
Yet, at Hunga Tonga Hunga Ha'apai, we were unable to predict what became the world's
largest volcanic eruption in the last decade.
So, why were we unable to predict this eruption?
The answer relates to how scientists predict volcanic eruptions.
Around the planet, scientists can often give more than a week's warning before a volcano
erupts, as we analyze data transmitted from sensors emplaced around a volcano's edifice.
Useful information which these high-tech sensors catch are harmonic tremor from volcanic activity,
and uplift from the intrusion of magma.
However, in the case of Hunga Tonga, this information was not available.
Why?
There were no sensors placed on or near the island.
This was not due to incompetence, but rather due to how expensive these systems are.
I asked the US Geological Service how much it would cost to place a single basic model
seismograph, and they quoted me $60,000 US dollars plus another $2,500 a year in upkeep.
For a volcano to be thoroughly monitored, at least three of these sensors alongside
ground deformation detecting equipment are needed.
Once everything is said and done, that totals around a quarter million dollars.
In the United States, such expenditures are possible.
It is not however possible in Tonga, as their citizens only make a combined $552 million
US dollars each year.
Thus, if the 18 active volcanoes within Tonga were to be all thoroughly monitored, a tax
increase would be necessary, and we all know how much people love taxes.
Also, from a geological perspective, there are several other volcanoes within Tonga which
are seemingly far higher risk volcanoes that have produced ancient eruptions an order of
magnitude larger than what Hunga Tonga Hunga Ha'apai produced on January 15th.
These include large islands such as Niuafoʻou and Tofua, which each contain a caldera with
a massive crater lake in their center.
Although Hunga Tonga was known to contain a large submarine caldera, so did the majority
of volcanoes within the small nation of Tonga.
As for why satellite data was not helpful?
Small islands are very difficult to get ground deformation data off of, as it can screw with
results if only a limited landmass is available.
My hope is that this eruption serves as a warning to other nations about the dangerous
of shallow submarine or small island volcanoes.
One such example of another island which could produce a large collapse at any moment in
the next century is the Kadovar volcano in Papua New Guinea.
As more information continues to pour in on the eruption, we can now get a better estimate
of the magnitude of what occurred.
We know that two separate landslides occurred, the second of which was associated with a
powerful volcanic explosion.
While the exact size of these interpreted landslides are unclear, I estimate that the
one on January 14th removed 100 million cubic meters of rock.
The landslide the following day was more voluminous, removing about 2 cubic kilometers of material.
While it is being widely reported that this is the first volcanic tsunami since the 1883
eruption of Krakatoa, this is not correct.
Volcanic tsunamis have occurred at 10 different volcanoes since then, with several of these
producing more than one collapse.
Thus, since the edifice of Hunga Tonga has collapsed, we can expect it to collapse again
at some point in the next century.
As for how rare far reaching volcanic tsunamis are, that is tsunamis which effect an entire
sea or ocean basin, those recur about every 70 years.
These past landslides provide a model of what will happen next at the Hunga Tonga Volcano.
Thanks for watching.
If you would like to request a specific topic, please leave a comment below!
Additionally, I would like to thank my new patron Robert Liaw for supporting this channel!