An Australian couple was visiting Papua New Guinea on Aug. 29 when a nearby volcano named Mount Tavurvur began to erupt. Hoping for a better view, they made a snap decision to hop on a boat from their hotel. Not only did they manage to see the eruption, but they happened to be watching — and filming — when the volcano suddenly exploded, releasing a giant ash cloud and a powerful shock wave.

Tavurvur seems deceptively calm as the video begins, but things change quickly. Its peak explodes about 12 seconds in, ejecting a plume of ash and debris as well as the visible — but not yet audible — arc of a shock wave. "Watch out for the shock; it's coming," someone on the boat warns. When the shock finally roars by 13 seconds later, it prompts an awestruck shout of "Holy smoking Toledos!"

Eruptions like this from Mount Tavurvur are not empty threats. The 732-foot (223-meter) stratovolcano has a long history of dangerous outbursts, including a lengthy one that killed about 500 people between 1937 and 1943. A 1994 eruption nearly destroyed the town of Rabaul, a provincial capital built in 1910 by German colonists who didn't realize they were living inside a caldera.

Tavurvur before eruption

Tavurvur after eruption

These satellite images show the landscape around Mount Tavurvur before and after its most recent eruption. (Photos: NASA)

Despite some evacuations, diverted flights and thick ash covering nearby forests (see satellite photos above), the latest eruption was minor by historical standards. But it still provided a once-in-a-lifetime spectacle for many witnesses, especially Phil and Linda McNamara, the tourists from Queensland whose impromptu boat trip has allowed people around the world to marvel at this wonder of nature.

"It was a spur of the moment thing to head out and film the volcano," Phil McNamara tells the Brisbane Times. "I thought I might as well try and capture something you rarely get to see."

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Russell McLendon ( @russmclendon ) writes about humans and other wildlife.