Tonga Shock Wave Created Tsunamis In Two Different Oceans (science.org)
- Reference: 0158034975
- News link: https://news.slashdot.org/story/22/01/26/0359248/tonga-shock-wave-created-tsunamis-in-two-different-oceans
- Source link: https://www.science.org/content/article/tonga-shock-wave-created-tsunamis-two-different-oceans
> When Hunga Tonga-Hunga Ha'apai, a mostly submerged volcanic cauldron in the South Pacific Ocean, exploded on January 15, it [2]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?
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> 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, [3]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.
[1] https://slashdot.org/~sciencehabit
[2] https://news.slashdot.org/story/22/01/19/0212214/nasa-scientists-estimate-tonga-blast-at-10-megatons
[3] https://www.science.org/content/article/tonga-shock-wave-created-tsunamis-two-different-oceans
I don't think this makes sense (Score:3)
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.
Re: (Score:2)
> 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: (Score:2)
Why are we taking the speed of sound in air rather than water?
Re: (Score:2)
The 'main' tsunami, the one that hit Japan, is the shock wave in water. I think, if I'm reading the article correctly, that the suggestion is that the shock wave in the air transferred enough momentum to water in the atlantic to cause a small (~10 cm) tsunami there too. That's why the OP is talking about the speed of sound in air. Here's a quote from TFA that seems relevant:
> 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.”
Also detected in Portugal (Score:1)
The Portuguese Meteorological Office (IPMA) has detected 40cm tsunami waves as well. According to them this should be caused by the atmospheric shock wave moving along the Atlantic.
Sweet. (Score:2)
Cowabunga, dude.