Η βίαιη έκρηξη του υποθαλάσσιου ηφαιστείου Hunga Tonga Hunga Ha’apai που έγινε το Σάββατο 16/1/22, «ακούστηκε» από τη Νέα Ζηλανδία έως και το Ηνωμένο Βασίλειο και την Ιταλία. Τι άκουσαν πραγματικά οι άνθρωποι και πόσο μακριά ταξίδεψαν τα ωστικά κύματα; Οι ειδικοί ερωτήθηκαν σχετικά και οι απαντήσεις τους παρουσιάζονται σε άρθρο στο www.nzherald.co.nz με τίτλο: Tonga eruption heard in New Zealand, pressure waves picked up in Europe.
Το άρθρο, γραμμένο στην αγγλική γλώσσα, αναφέρει μεταξύ άλλων και τα εξής:
Hunga’s eruption injected a huge amount of energy into the atmosphere, said Richard Easther, Professor of Physics at the University of Auckland. “The bigger the explosion, the more air is stirred up, so the louder it’s going to be.”
“It’s not one continuous wall of sound, it’s a pulse of sound that works its way out, spreads out effectively as a circle centred on the volcano.”
People in the North Island would have heard it before people in the South Island.
Sound travels about one kilometre every three seconds, so what New Zealanders heard would have taken place about two hours earlier in Tonga, some 2400km away, estimates Dr Marcus Wilson, senior lecturer of Physics at the University of Waikato.
A single blast would disperse as the sound travels, arriving as a lasting rumble that can take many seconds to pass. “It will be the really low sounds you’re hearing, a really deep rumbling.”
“Some people will hear it more strongly than others … these are pressure waves, basically squashing and stretching the air.”
Some social media posts called it a “sonic boom” but experts say that’s a misnomer.
A sonic boom is a shock wave produced by something travelling faster than the speed of sound, like the Concorde or high-performance fighter jets.
Easther says the eruption may have produced a sonic boom at the source, but by the time the pressure wave arrived in New Zealand it would have been moving as regular sound.
On the other side of the world, the UK Met Office picked up shockwaves of the Tonga volcano on its observation sites, confirming earlier readings from weather enthusiasts.