Scott Manley presents a compilation of satellite imagery, on-the scene photos, comparison of the islands over time, the tsunami coming ashore, lightning strike tracking, and stunning visualisations of the pressure wave passing over Japan and across the United States.
It may be obvious to you science gents, but it isn’t to me: will this eruption cause widespread climate effects like that eruption in the 19th century which resulted in snow in New England in June? Or like in 632 AD , where there are contemporary reports that after a large eruption the sun was veiled for a year?
And inky-dinkally, if/when the volcanic cloud spreads far and wide, isnt it gonna show even more clearly that we cannot realistically depend on solar power?
I know! Let’s send Greta Thunberg to yell at the volcano:
“ How DARE you!?!” That’ll teach it….
A language purist would say that such effects from very large volcanic eruptions are weather effects rather than climate effects. The volcanic dust in the atmosphere causes changes in weather patterns for a year or two, after which the annual weather cycle resumes its normal variability. A weak analogy is to a plumb bob – set it swinging and it will swing for a while before returning to its prior stationary equilibrium.
A climate effect would be an Ice Age, of which the planet has had many, with presumably many more to come. That is when the weather patterns do not return to previous variability but change to a different equilibrium. What caused such genuine “climate change” is a good question, with a number of contested proposed answers. But we know there have been larger volcanic eruptions within historical times which have caused temporary weather effects but not long-term climate change.
If volcanic dust does cause a temporary cooling, maybe governments should pass laws to require everyone to leave their SUVs running all the time, to prevent the weather effects by generating more offsetting carbon dioxide? Just a suggestion!
I read that Yellowstone is a huge caldera and eruption is overdue and when it blows it will cut the continental US in half!
True?
And Gavin, yes, okay, the volcanic effect would just be a weather change, not “climate change”—but whatevs, it should cause us to rethink the getting rid of fossil fuels mantra. That doesn’t mean it will but it should. I don’t think I’ve ever seen volcanoes taken into account in any discussion about climate change, come to think of it.
Large volcanic eruptions cause temporary decreases in global temperature largely due to dispersal of sulfates in the upper atmosphere. The very large eruption of Tambora in 1815 caused global cooling of 0.53° C. The size of volcano eruptions is characterised by the Volcanic Explosivity Index (VEI) which is a logarithmic measure of the volume of ejecta from the eruption. Tambora was a VEI-7 event, and such events are estimated as occurring every 500 to 1000 years.
This eruption is estimated to be a high VEI-5 event, which category occurs around every 12 years (with most being toward the low end of VEI-5, however). That is the category of Mt. St. Helens. The last VEI-6 event was Pinatubo in 1991. Even a VEI-7 event, however, would not dramatically decrease the power generated by photovoltaic panels, although local disruption (comparable to thick cloud cover) would occur downwind of the eruption until the plume dispersed. Pinatubo caused global cooling of around 0.4° C and beautiful sunsets for months, but no obvious decrease in solar intensity. The Tonga eruption is substantially smaller.
In terms of the Volcano Explosivity Index I mentioned in comment 12, the last Yellowstone caldera eruption in 630,000 B.C. was estimated to be VEI-8, releasing more than 1000 km³ of ejecta, or around 1000 times more than the Tonga volcano and ten times Tambora. Based upon ash deposits, the last Yellowstone super-eruption is estimated as having released 2,500 times as much ash as Mt. St. Helens.
Here is a tweet with an animated GIF of the pressure wave from the Tonga eruption crossing Germany, Switzerland, and Austria. For some reason animated GIFs from Twitter will not embed here.
The best part of these large volcanic events is the sunsets, which endure for many months. Pinatubo gave us some great ones in 1991-92. I don’t have any pictures of those but there are some nice ones of the Agung eruption of 1963 in Aden & Marjorie Meinel’s Sunsets, Twilights, and Evening Skies. If we’re lucky, this latest will also give us some good ones. Look to the west long after sunset (or east before sunrise if you’re an early riser).
The time the glow lasts after sunset depends on the altitude of the volcanic stratum. This handy graph lets you find one from the other.
The eruption is listed as occurring at 4:15:45 (4.26) UTC. KLAX is 8550 km from Tonga. The pressure peak at KLAX is 11.9 UTC. The computed speed of the pressure wave is 310 m/s, in good agreement with your value of 300 m/s. The speed of sound is 310 m/s at about 7000 m altitude.
From New Zealand, the 1st Wave is the direct pressure spike arriving from Tonga. The 2nd Wave is the pressure wave arriving that went the long way around the world from the original event. This is followed by a spike from the first wave arriving after circumnavigating the globe.
Literally, a bang heard 'round the world.
Here is a global image showing the propagation of the pressure wave from the volcanic explosion. This is a Twitter animated image which cannot be embedded: click the link to view.
Building on the calculations in comments 7 and 18, I performed a similar analysis on the propagation of the first wave signal around the world reported from New Zealand in comment 19.
Absent exact numbers, I eyeballed the chart and estimated the arrival of the first wave on 2022-01-15 at 20:00 UTC and return of the first wave after circumnavigation on 2022-01-17 at 07:20 UTC, for a propagation time of 35.33 hours. I then calculated the velocity in both metres per second and nominal Mach units with Units Calculator:
(earthradius 2 pi) / (35.33 hour) = 314.73281 metre/second
(earthradius 2 pi) / (35.33 hour) = 0.94953481 mach
where
mach = 331.46 metre/second
which is the definition in GNU Units for the speed of sound in dry air at standard temperature and pressure.
Given the uncertainties of propagation around the globe and time measurement from the graph, this seems a perfectly reasonable value.
You’d expect the propagation speed to be somewhat less than it is at standard temperature and pressure (STP) since the sound channel is at some nontrivial altitude where the temperature, and hence the speed of sound, is less than it is at sea level. Sound is lazy; it bends toward the slower regions. Just as there’s a sound channel deep in the ocean, so there is one in the atmosphere. Wind and temperature gradients also affect the propagation of sound. All of which is to say that one would expect the average speed of propagation to be less than the speed of sound at STP, though it’s complicated to work out exactly what it would be.
“Standard temperature and pressure” (STP) is defined (since 1982, trivially different before) as 0 °C and 100 kPa (essentially, one atmosphere). But this isn’t really “standard” outside of polar regions, since at sea level the average temperature is greater than freezing.
Given the uncertainties about the altitude at which the pressure wave propagated (which doubtless varied substantially as it went around the globe) and the temperature along its path (plus humidity, which also gets into the speed of sound game), I was just satisfied it came out so close to the “around 300 metres per second” that Kerbal Space Program trains players to expect.
This is an update from GeologyHub which shows some early radar imagery that appears to show the bridge between the two islands and much of the islands themselves were blown away in the explosion. It then presents an analysis which concludes the based upon sulfur dioxide emissions this was likely a Volcano Explosivity Index (VEI) 4 or low 5 event. The estimates of a higher index based upon the size of the immediate explosive plume may not have taken into account the effect of seawater turned to vapour in the underwater eruption, which increased the plume height from which VEI is often estimated.
Here is a news report from Newshub in New Zealand about damage in Tonga and relief efforts being staged from Australia and New Zealand.
The Swiss Seismological Service detected both the seismic waves from the Tonga eruption and the infrasonic atmospheric pressure wave on both its primary arrival, arrival along the long arc around the Earth, and on subsequent circlings of the globe.
The massive submarine eruption of the Hunga-Tonga-Hunga-Ha’apai volcano in the South Pacific on 15 January 2022 was registered by the seismic stations of the Swiss Seismological Service at ETH Zurich (SED). The volcanic explosion began at 05:14 Swiss time and generated seismic waves equivalent to a magnitude 5.8 earthquake. Seismic body waves reached the Swiss seismic network around 20 minutes later, having passed directly through the Earth. Body waves propagate at speeds of 5–10 km/second (36,000 km/h). Another 30 minutes later, seismic surface waves – which travel more slowly – also reached Switzerland. The Swiss network continued to record the Earth ‘ringing’ in normal mode for more than 12 hours after the surface waves had subsided. This is where the Earth vibrates at characteristic frequencies determined by its internal structure. These vibrations, with a period of approximately 4.5 minutes, were also observed after the eruption of the Philippine volcano Mount Pinatubo in 1991.
Such volcanic explosions also create pressure waves in the atmosphere, as described in this MeteoSwiss blog (in German). Infrasound waves, which have frequencies below the lower limit of human audibility (between approximately 15 Hz and 0.001 Hz), are only slightly attenuated in the atmosphere and can be measured over very long distances. Infrasound travels at a speed of around 1,200 km/h. These waves showed up clearly on the SED’s highly sensitive broadband monitoring stations and on SED-operated infrasound sensors from around 20:30 Swiss time, a little over 15 hours after the seismic waves reached Switzerland. The dispersion of these infrasound waves (i.e. the way their propagation velocity depends on their frequency) can also be clearly seen, with low frequencies propagating slightly faster and arriving first, followed by progressively higher frequencies. An initial period of strong signals lasting a good two hours was caused by the waves that reached us directly. Around five hours later, the signals that propagated in the opposite direction can be seen, with significantly smaller amplitudes. Another spike was observed on the morning of 17 January as the waves circled the Earth for a second time. The infrasound signals caused a number of false seismic triggers during automatic data processing at the seismic monitoring stations.