Tonga eruption: Is it the loudest event in history?

An undersea volcano near Tonga erupted, sending waves thousands of kilometers across the ocean. Waves about three feet high hit parts of Alaska Saturday morning. But hours before those waves arrived, the sounds of the blast reached the homes of many Alaskans. The eruption near Tonga was so powerful that it was heard even in Alaska!

Data from UAF researchers tracks the sound wave from the blast as traveling at about 700 mph. Hearing a volcano or any sound so far from its origin is quite a rare occurrence. Sound travels slowly through the atmosphere. Tonga's explosion was heard in Alaska about 7 hours after the explosion.

Scientists often record really low-frequency sound waves around the world after large volcanic eruptions or explosions, but it's rare enough that ordinary people can hear them distinctly.

Alaskans from Anchorage to Fairbanks and Cordova, along the Kenai Peninsula and elsewhere reported deep booms and thunder-like explosions early Saturday morning. The sounds were also heard in Canada.

There have been only a few other times when an audible sound has traveled this far, including the 1912 eruption of Novarupta Katmai, the largest eruption of the 20th century, and the eruption of Krakatoa in 1883. Tonga's eruption is likely to rewrite noise history.

The fact that Alaskans could hear any sound of the eruption indicates how large this volcanic eruption really was. The audible sounds from the eruption lasted about 30 minutes, while the low-frequency sounds lasted longer, about 2 hours.

The pressure wave of the eruption from a volcano 17,000 kilometers away "arrived" in Slovakia. But we didn't hear the sound.