3 ms·

US tsunami monitoring has a record. https://www.tsunami.gov/previous.events/?p=03-19-09-Tonga https://www.tsunami.gov/previous.events/?p=03-19-09-Tonga

sandworm101 5y ago
A tsunami is a wave. Not sea level. Waves literally come and go over a period of seconds to minutes. They wobble back and forth without actually moving much water. Sea levels move on the order of hours and days and involve the physical movement of literally hundreds of cubic-miles of water. Raising or lowering a sea level measurement (not a temporary wave) requires far more energy than a volcano. From the link: "Listed wave heights are maximum amplitude in cm (above sea level)." In other words, even tsunami waves heights are not changes to sea level.
- TheOtherHobbes 5y ago
  I don't think anyone - except perhaps you - is suggesting that the eruption caused an actual rise in sea levels.
  - andrewflnr 5y ago
    They were initially responding to a comment that said sea levels were slightly elevated for a week after the eruption. I have to agree that's pretty weird even for a tsunami.
- thaumasiotes 5y ago
  > A tsunami is a wave. Not sea level. Waves literally come and go over a period of seconds to minutes. They wobble back and forth without actually moving much water. Sea levels move on the order of hours and days and involve the physical movement of literally hundreds of cubic-miles of water. You should be aware that tsunamis behave in the way you're calling "sea level", and not in the way you're calling "wave". It's true that a tsunami is a wave, but it's not true that they come and go over a period of minutes, or that they fail to move much water. They're very large.
  - sandworm101 5y ago
    Some of them, specifically those involving undersea plates moving upwards, but even those do settle out quickly. That is why the term literally means "port waves" because they bypass normal wave protections and move into ports, similar to how tidal bores move up rivers. But the comment above spoke of sea levels being impacted for many days, something beyond even thrust tunamis and more akin to hurricanes.
- lnwlebjel 5y ago
  Think of it more like a very long period wave, much like a tide, but on a much shorter time period than the tide. Tides, waves (periods on the order of seconds), and tidal waves (or tsunamis) are all fluctuations in sea level. Water can be moved when the waves encounter enclosed bays or harbors. Think of the water level dropping 3 ft over 20 minutes in front of a harbor entrance and imagine the currents that can result. Here's an example of observations from coastal California (red line shows sea level measured every 6 minutes: https://tidesandcurrents.noaa.gov/waterlevels.html?id=9412110&bdate=20220114&edate=20220115&units=standard&timezone=LST/LDT&interval=6 https://tidesandcurrents.noaa.gov/waterlevels.html?id=941211... It is truly amazing - I'm not surprised that it's hard to believe.
  - sandworm101 5y ago
    If it has a period not tied to the rotation of the earth (ie tides) then it is not a change in sea level but a wave. And Tsunami does not translate as "tidal" wave. It means "port wave" and has nothing to do with tides whatsoever.
- samatman 5y ago
  A tsunami is an entirely different kind of wave than a normal wave. A normal wave is transverse, and a tsunami is a pressure wave. The first bobs the water up and down and the wave moves forward, the second shoves water ahead of it, displacing it upward into the wave. The tsunami won't break when the column gets short, but rather transfer all of the energy of moving a deep water column to a shallow one. That's what makes them dangerous.
NamTaf 5y ago
That's from 2009. I can't figure out how to navigate the site so as to find the 2022 event.

sandworm101 5y ago

A tsunami is a wave. Not sea level. Waves literally come and go over a period of seconds to minutes. They wobble back and forth without actually moving much water. Sea levels move on the order of hours and days and involve the physical movement of literally hundreds of cubic-miles of water. Raising or lowering a sea level measurement (not a temporary wave) requires far more energy than a volcano. From the link: "Listed wave heights are maximum amplitude in cm (above sea level)." In other words, even tsunami waves heights are not changes to sea level.

TheOtherHobbes 5y ago
I don't think anyone - except perhaps you - is suggesting that the eruption caused an actual rise in sea levels.
- andrewflnr 5y ago
  They were initially responding to a comment that said sea levels were slightly elevated for a week after the eruption. I have to agree that's pretty weird even for a tsunami.
thaumasiotes 5y ago
> A tsunami is a wave. Not sea level. Waves literally come and go over a period of seconds to minutes. They wobble back and forth without actually moving much water. Sea levels move on the order of hours and days and involve the physical movement of literally hundreds of cubic-miles of water. You should be aware that tsunamis behave in the way you're calling "sea level", and not in the way you're calling "wave". It's true that a tsunami is a wave, but it's not true that they come and go over a period of minutes, or that they fail to move much water. They're very large.
- sandworm101 5y ago
  Some of them, specifically those involving undersea plates moving upwards, but even those do settle out quickly. That is why the term literally means "port waves" because they bypass normal wave protections and move into ports, similar to how tidal bores move up rivers. But the comment above spoke of sea levels being impacted for many days, something beyond even thrust tunamis and more akin to hurricanes.
lnwlebjel 5y ago
Think of it more like a very long period wave, much like a tide, but on a much shorter time period than the tide. Tides, waves (periods on the order of seconds), and tidal waves (or tsunamis) are all fluctuations in sea level. Water can be moved when the waves encounter enclosed bays or harbors. Think of the water level dropping 3 ft over 20 minutes in front of a harbor entrance and imagine the currents that can result. Here's an example of observations from coastal California (red line shows sea level measured every 6 minutes: https://tidesandcurrents.noaa.gov/waterlevels.html?id=9412110&bdate=20220114&edate=20220115&units=standard&timezone=LST/LDT&interval=6 https://tidesandcurrents.noaa.gov/waterlevels.html?id=941211... It is truly amazing - I'm not surprised that it's hard to believe.
- sandworm101 5y ago
  If it has a period not tied to the rotation of the earth (ie tides) then it is not a change in sea level but a wave. And Tsunami does not translate as "tidal" wave. It means "port wave" and has nothing to do with tides whatsoever.
samatman 5y ago
A tsunami is an entirely different kind of wave than a normal wave. A normal wave is transverse, and a tsunami is a pressure wave. The first bobs the water up and down and the wave moves forward, the second shoves water ahead of it, displacing it upward into the wave. The tsunami won't break when the column gets short, but rather transfer all of the energy of moving a deep water column to a shallow one. That's what makes them dangerous.

NamTaf 5y ago

That's from 2009. I can't figure out how to navigate the site so as to find the 2022 event.