Volcanoes are one of Earth's most destructive forces of nature; spewing out massive amounts
of lava, rock, and superheated ash. There are many historic volcanic eruptions, from Mount
Vesuvius to Krakatoa. Now another big volcano has found its way onto the pages of history.
On January 14, 2022, a huge underwater volcano in the South Pacific Ocean awoke
from a seven-year slumber…and on the next day it would erupt with NASA satellites
capturing amazing images of the big and powerful eruption.
Scientists say everything about this volcanic eruption is ‘off-the-scale weird’. Including
the incredible shockwave it sent around the world. What series of geological events led
to the powerful and massive eruption, and is this a sign that more volcanoes will erupt soon?
Get ready to discover the answers, and experience one of Earth's most powerful forces of nature!
[INTRO]
For many years, the Hunga Tonga-Hunga Ha'apai volcano could be seen poking
out from the water in the South Pacific Ocean as a pair of small rocky islands;
one named Hunga Tonga, and the other Hunga Ha’apai.
Below the surface of the ocean, this volcano is located
65 kilometers [40 miles] north of Tongan capital Nuku’alofa and belongs to a vast
arc of volcanoes and ocean trenches known as the Pacific Ring of Fire.
Back in 2014, an eruption created a third island that connected the two islands into
one large landmass. The volcano continued to be quietly active for several years,
and the island became bigger. On December 20, 2021, the volcano erupted and sent a
large plume of ash into the sky that could be seen 70 kilometers away. Despite this,
the volcano was declared dormant by the Tonga Geological Services on January 11,
2022. The volcano became active again, and on January 14, tsunami warnings were sent out.
But then on Saturday, January 15, 2022, the volcano unexpectedly erupted.
NASA satellites captured images of the event, and say the Tonga volcano eruption was 500 times
more powerful than the Hiroshima atomic bomb; the blast equivalent to 10-18 megatons of TNT.
A dramatic piece of footage was captured on a smartphone
and shows people looking at the ash plume in the sky from the eruption,
and then moments later the sound and blast from the shockwave hits them.
A smartphone also captured the shockwave from the volcanic eruption on Lakeba, Fiji.
The shockwave from the Tonga volcanic eruption was very powerful,
and among the largest ever recorded, with some researchers saying it’s
similar to the one produced by the 1883 eruption of Krakatoa.
The shock waves traveled outward in all directions at 305 meters per
second, [1,100 km/h 680 mph] close to the speed of sound, and caused the Earth’s atmosphere to
ring like a bell. In fact, GPS satellites detected disturbances in the ionosphere, the layer of the
atmosphere just above the stratosphere, at heights of 80-90 kilometers [50-55 miles] and barometers
all over Europe detected atmospheric pressure changes of 2 to 3 millibars.
This is a capture from the GOES-17 satellite in
infrared. You can see the shock waves travel outward from the eruption.
That first shockwave you see circled the entire planet twice in one day!
But that is not all the surprises this Tonga submarine volcanic eruption had…
Tsunamis that are caused by volcanoes come from an underwater shift,
usually created by landslides from the flanks of a collapsing volcano during an eruption.
Still, it is rare for a submarine volcano to trigger tsunamis. In fact, 90 percent of tsunamis
are triggered by earthquakes. However, scientific instruments discovered that this new eruption
triggered pressure waves and gravity waves, which in turn triggered ‘airblast’ tsunami waves
all around the Pacific Ocean and even in distant ocean basins. Even the United States West Coast
and Hawaii went under a tsunami advisory. These tsunami pressure waves traveled clear across
the planet, and in Santa Cruz, California, huge ocean waves crashed into sea walls,
and even more incredible, the tsunami caused Soquel Creek in Santa Cruz to flow backwards.
Tsunami waves that are driven by gravity travel around 200 meters [660 feet] per second,
about as fast as a passenger jetliner. We mentioned the shockwave was so powerful
that it caused the atmosphere to ring like a bell.
By the transfer of this energy from the atmosphere to the ocean, the shockwave amplified ocean waves
around the world, pushed them farther out and accelerated their normal travel time.
But scientists had never seen anything like this before, and tsunami warning centers
aren’t equipped to handle tsunamis caused by pressure or gravity waves.
It looks as though tsunami centers need an upgrade to detect these atmospheric pressure waves.
The NASA Earth Observatory said the volcano spewed ash and volcanic material
as high as 40 kilometers into the atmosphere, nearly halfway into space!
The ash plume of the volcano measured 38 kilometers [24 miles] at the time
of the initial eruption…but in an hour, it spread out at 650 kilometers in diameter.
A cloud big enough to cover most of Florida or California USA.
However, even though the plume looks massive, this latest eruption is strange because the
incredibly energetic explosion from the volcano ejected a surprisingly low amount of material.
Ash from the volcano’s past eruptions can be found on the nearby island of Tongatapu,
which is 10 times thicker than the new layer.
But scientists are still trying to figure out the big question...why was the Tonga
volcano eruption so violent? Volcanoes in deep water rarely erupt through the ocean surface
in big blasts. This is because overlying water, or water over the top of a volcano,
prevents gas bubbles from forming and growing with explosive force.
However, the volcanic vent that erupted at Hunga Tonga–Hunga Ha‘apai was just 10
to 250 meters deep. That’s shallow enough that water didn’t suppress the power of the blast,
but just deep enough for the erupting magma to meet a lot of water. And water can fuel
explosive eruptions by flash-heating to form steam which expands very quickly.
The temperature of magma usually exceeds 1000 degrees Celsius,
and seawater is around 20°Celsius. The mixing of the two inside the confined space of a magma
chamber would be incredibly explosive, and this is likely why the eruption was so powerful.
But another important factor is the amount of volcanic gas that is mixed into the magma
before the volcano erupts. Volcanologists say that a gas-rich upwelling of magma could have
fed the January 15th eruption giving it a large number of gas bubbles to fuel the explosion.
Back closer to the epicenter, the volcano's blast
severed the underwater fiber-optic cable that connects Tonga to the outside world,
essentially plunging the nation of 105,000 people into digital darkness. The small island
that the volcano had created over the past few years was obliterated, and the Sun was
blotted out from the sky by the thick ash and small stones that rained from the sky…leaving
those who were fleeing to higher ground in what must have been a grim and apocalyptic scene.
A ship and its crew have been tasked with repairing the submarine cable that connects
Tonga to Fiji and was likely severed by the eruption. However, it is not clear if
the cable was buried by a landslide coming off the volcano, or cut in several places.
The volcano also triggered one of the largest volcanic lightning events ever recorded. The
surrounding islands in the Tonga archipelago were completely engulfed in lighting during
different stages of the eruption which lasted for days. On January 13, 2022, a small blast above
the surface caused a major lighting event that lasted throughout the day. But on January 15,
2022 after the massive underwater eruption, almost 400,000 lighting strikes were recorded
in just six hours. It was extraordinary because the 2018 Anak Krakatau eruption only saw 340,000
lighting events over a week period. So to see so many in just a few hours is incredible.
Despite the danger from the eruption, the Tongans were well-equipped to deal with
the tsunami that the eruption sent their way. In fact, the small island nation is considered among
the most prepared for natural disasters, and most people knew to evacuate to higher ground.
The huge and violent eruption might have been a surprise to some, but there were warning signs
that the volcano could erupt at any moment, even though the volcano was declared dormant.
On December 30, 2021, a huge plume of ash erupted from the volcano, followed by another equally
huge plume just before the big eruption. Both of these plumes had very little volcanic material.
However, they contained a lot of gas. And gloopy magma filled with gas is a recipe for disaster.
These two volcanic belches indicated that there was a lot of trapped gas
signaling an epic blast was yet to come.
One of the strange things is there are no seismometers set up to study
earthquakes in the surrounding area, and no active seismometers in Tonga…so
any earthquakes prior to the massive eruption were not tracked in much detail.
There is some data that shows quakes can be generated by fresh magma rising into
the crust to refill a reservoir that was now empty from a large eruption.
Now scientists want to survey the sea-floor around the Hunga Tonga–Hunga Haʻapai volcano,
which rises 2 kilometers from the seafloor. But for now,
it is too dangerous to approach this volcano. Early data shows the Tonga
event could measure as high as 5 on the volcanic explosivity index, which is an 8-point scale.
So will there be other big volcanic eruptions?
The total number of undersea volcanoes on Earth is around one million, which like continental
volcanoes, are located near the Earth’s tectonic plates where they form. That’s a lot of volcanoes,
and 75,000 of these volcanoes rise more than 1 kilometer above the seabed.
Nearly three-quarters of all volcanic activity on Earth actually occurs underwater.
But there isn’t any reason to worry now, because most of those million or so volcanoes are extinct,
and only 119 submarine volcanoes in the Earth’s oceans have been known to erupt
over the last 11,700 years. And experts say volcanic eruptions that register 5
on the Volcanic Energy Index usually only happen once or twice in a decade.
But the Hunga Tonga-Hunga Ha'apai volcano is surely not finished yet, and
The Tonga Geological Services are keeping an eye on the volcano. Right now, there are three things
that could happen: the eruption could be over, the volcano could stay active at a lower level,
or there could be another massive blast. Earthquakes and aftershocks were reported
days after the blast. There is just no telling when a volcano is going to erupt next.
The Tongan people have been heavily affected by the blast and can no longer rely on the ocean
for fishing because of the toxic ash. To make matters worse for fishing, Peru declared an
environmental emergency after almost a million liters of crude oil spilled into the sea when a
tanker was hit by the big waves while unloading at a refinery. The spill has covered beaches and
harmed fishing industries, and local crews are working non-stop to clean up the mess.
Because of travel advisories due to the pandemic, only the local people can rebuild. But there is
help, and they are slowly getting back on their feet after this terrible natural disaster.
So feel good about donating what you can to your favorite charity.
And as always, if something changes, and we see another volcano eruption,
we’ll keep you up to date. So stay tuned here, and thanks for watching.