Tonga Shock Wave Created Tsunamis In Two Different Oceans (science.org) 25
sciencehabit shares a report from Science.org: When Hunga Tonga-Hunga Ha'apai, a mostly submerged volcanic cauldron in the South Pacific Ocean, exploded on January 15, it unleashed a blast perhaps as powerful as the world's biggest nuclear bomb, and drove tsunami waves that crashed into Pacific shorelines. But 3 hours or so before their arrival in Japan, researchers detected the waves of another small tsunami. Even stranger, tiny tsunami waves just 10 centimeters high were detected around the same time in the Caribbean Sea, which is in an entirely different ocean basin. What was going on?
Researchers say there is only one reasonable explanation: The explosion's staggeringly powerful shock wave, screaming around the world close to the speed of sound, drove tsunamis of its own in both the Pacific and Atlantic oceans. It's the first time a volcanic shock wave has been seen creating its own tsunamis, says Greg Dusek, a physical oceanographer at the National Oceanic and Atmospheric Administration who documented the phenomenon using a combination of tide and pressure gauges around the world. But, "It's almost certainly happened in the past," says Mark Boslough, a physicist at the University of New Mexico, Albuquerque. The discovery suggests the shock waves generated by explosive eruptions in Earth's history, and by other violent cataclysms, like the airbursts of comets or asteroids colliding with the planet's atmosphere, may have also created transoceanic tsunamis, perhaps with considerably bigger waves.
Researchers say there is only one reasonable explanation: The explosion's staggeringly powerful shock wave, screaming around the world close to the speed of sound, drove tsunamis of its own in both the Pacific and Atlantic oceans. It's the first time a volcanic shock wave has been seen creating its own tsunamis, says Greg Dusek, a physical oceanographer at the National Oceanic and Atmospheric Administration who documented the phenomenon using a combination of tide and pressure gauges around the world. But, "It's almost certainly happened in the past," says Mark Boslough, a physicist at the University of New Mexico, Albuquerque. The discovery suggests the shock waves generated by explosive eruptions in Earth's history, and by other violent cataclysms, like the airbursts of comets or asteroids colliding with the planet's atmosphere, may have also created transoceanic tsunamis, perhaps with considerably bigger waves.
Sweet. (Score:1)
I don't think this makes sense (Score:5, Interesting)
Eruption happened at 04:14 UTC, Tsunami hit Japan at 14:14 UTC. Three hours before that would be 11:14 UTC, but the shockwave was travelling at the speed of sound, which is around 761mph at sea level. The Caribbean is at least 7,000 miles away, so at the speed of sound it would take around 9hrs 30mins to get there, which would mean 13:44 UTC at the absolute earliest - only 30mins before the Japanese tsunami, not 3 hours before. Furthermore, if the shockwave itself was causing tsunamis this doesn't explain why the first Japanese tsunami happened after the first Caribbean one; you'd have expected shockwave driven tsunamis to appear in Japan before the Caribbean ones regardless, even if the main tsunami driven by the displacement of water at the site of the eruption itself took longer to arrive.
I appreciate it's possible the suggestion is that the shockwave passed through the core of the planet or similar rather than around the surface, but I'm not convinced they're not simply confusing correlation for causation here. I suspect more likely what happened is that movements within the earths core or crust that triggered the Tonga eruption also triggered a minor eruption or shifting of plates causing an underwater landslide somewhere in the Atlantic around the same time as the eruption near Tonga resulting in the minor tsunami seen in the Caribbean. This would be a far more plausible explanation because it would actually be physically possible in the timeframes given for starters.
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I suspect more likely what happened is that movements within the earths core or crust that triggered the Tonga eruption also triggered a minor eruption or shifting of plates causing an underwater landslide somewhere in the Atlantic around the same time as the eruption near Tonga resulting in the minor tsunami seen in the Caribbean
That's reasonable, but wouldn't it show up on seismometers?
Re:I don't think this makes sense (Score:5, Interesting)
Probably:
https://earthquaketrack.com/r/... [earthquaketrack.com]
"North Atlantic Ocean has had: (M1.5 or greater)
6 earthquakes in the past 24 hours
51 earthquakes in the past 7 days
190 earthquakes in the past 30 days
3,109 earthquakes in the past 365 days"
Interestingly that page shows there was a magnitude 5.3 in the last 24 hours alone along the mid-Atlantic ridge. Unfortunately the page is a bit shit to navigate so I can't find an easy way of seeing the data for the 15th.
I think the problem is though that these things happen all the time, whether they cause any surface water movement though is dependent entirely on very unique circumstances of each one. You could have a magnitude 6 that no one notices because it had no real impact, but a magnitude 3 that just happens to trigger a massive underwater landslide resulting in a tsunami.
Having shore dived the Caribbean regularly, sometimes doing 5 dives a day and knowing that the waves can vary within a range of fuck all to a metre or so high in the space of just a few hours separate from standard tidal movements if the winds pick up. I'd wager there are plenty of 10cm tsunamis but the vast majority will simply be lost in natural variation of the waves driven by weather. This one was probably only noticed simply because someone was looking at tidal variation at the time of a big, internationally well publicised tsunami and has as a result gotten themselves a bit overexcited theorising without really thinking it through.
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A 10cm tsunami can easily cause a 3m high flood in the right (or wrong) coastal areas.
But you are right, islands would not be really affected.
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Why are we taking the speed of sound in air rather than water?
Re:I don't think this makes sense (Score:4, Informative)
But strong weather events can also create shoreline wave surges, called meteotsunamis. Creating one requires a sustained atmospheric disturbance with a substantial pressure drop or jump. That air pressure wave also needs to move at roughly the same speed as the sea’s waves. As the waves travel together, Dusek says, “You just keep feeding energy into that wave, and it builds up and up and up.”
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Because you should:
a) have learned how fast speed of sound is in the air in school
b) no laymen knows how fast it is in water
c) obviously a water shockwave hardly can be as fast as the speed of sound in water - at least not if caused by a mere vulcano
But if you know out of your mind how fast sound is in water: enlighten us ....
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Not sure what your point is here? Speed of sound in water is roughly 4x the speed of sound in air. Depending on air pressure, and water/air temperature etc. And I'm definitely a layman with only a high school knowledge of physics.
Shockwaves by definition travel faster than the speed of sound in any given medium,
Also, what??? 'mere vulcano'? Volcanos can produce massive explosions with unimaginable amounts of energy. Granted the Tongan volcano eruption released only as much energy as a small nuclear bomb
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Perhaps you should look on a map.
How exactly should a shock wave in water from Tonga hit the Caribbean?
The most likeliest solution is indeed that there was a shock wave in the earth crust doing it or a second event that coincidentally happened around the same time.
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Meh. The speed of sound, through air (gas) at the surface, is what you are calculating from. The speed of sound through water (liquid) is faster.
The speed of sound through the surface of the crust (solid rock) is much faster. A shock wave travelling through the crust will enervate the water above it as it passes into the Atlantic basin.
There is nothing in the sfa that remotely presents the idea that an aerial shockwave caused a tsunami. They don't and didn't.
The difference between shockwaves and soundwaves (Score:2)
Shockwaves move faster than the speed of sound [wikipedia.org]. I'm assuming that as it propagated around the earth it lost velocity until it became a regular sound wave again, losing energy in the process. A simple linear extrapolation is probably not going to make sense, even if you knew the initial velocity.
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Also detected in Portugal (Score:5, Informative)
There is only one ocean. (Score:2)
'nuff said.
I'm wondering if there is more to this ? (Score:2)
From a really old slashdot post about 12-15 years ago, I recall the mention of a specific atomic particle that entered and exited the earth. it left a signature on earthquake detection equipment. so if an atom could be picked up traversing the earth, then with some basic trial and error we could guess at some conclusions.
Now let's reverse a few of the posted notes:
10 CM detected in Jamaica,
40 CM detected at Portuguese Meteorological Office.
2 sources with time stamps. maybe if a third was found you could the
Near the antipode of Tonga (Score:2)
Not quite (the exact antipode is in Africa, near the West coast). But a wave propagating from Tonga would decrease in amplitude as it moved away from its source. But then arriving via numerous paths on the opposite side of the Earth, this would be about where it would constructively interfere (assuming a spherical cow in a vacuum and all that).
Smart people could probably access some sort of ocean model and calculate the path lengths around the southern tip of Africa, the southern tip of South America and t
10cm?? (Score:2)
How do you spot a 10cm tsunami? How does it look different than regular waves coming in & out?
Reply (Score:1)