Volcanic Airwave | John Seach

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An air wave is seismic energy transmitted through the atmosphere. Air waves can be seen close up to active vents when they disrupt eruption clouds.

For an observer the visual representation of the wave through the cloud precedes both projectiles and sound.

An explosion in an open vent produces a strong shock wave in the air which shows up as a high-frequency air-wave phase on nearby seismographs. Explosions which are contained within the volcano cannot couple with air, so that the radiated energy is transmitted only through seismic waves, producing a low-frequency seismic event.