Tavurvur Eruption 2014: Shock Wave Video from Rabaul, Papua New Guinea

On 29 August 2014, an Australian couple, Phil and Linda McNamara, were on a boat near Rabaul in Papua New Guinea when Mount Tavurvur exploded in front of them. Their camera caught the blast, a ring of shock wave racing out through the sky and, about 13 seconds later, the bang reaching the boat. The clip spread around the world within days and is still a textbook example of a volcanic shock wave caught on camera.

Tavurvur and the Rabaul caldera

Tavurvur is a 688-metre stratovolcano on the eastern rim of the Rabaul caldera, at the tip of the Gazelle Peninsula on New Britain island in East New Britain province. It is the most active vent in the caldera, and the town of Rabaul lies inside the caldera itself.

Living with the volcano has a long history:

• 1937: Tavurvur and its neighbour Vulcan erupted together, killing more than 500 people. The disaster led to the founding of the Rabaul Volcano Observatory.
• 19 September 1994: both volcanoes erupted again, destroying Rabaul airport and burying most of the town in heavy ash. Thanks to disaster planning, only five people died, one of them struck by lightning.
• 29 August 2014: Tavurvur began a new eruption at around 3:30 to 4:00 a.m. local time, sending ash about 15 to 18 km high. Nearby communities were evacuated and Rabaul residents were told to stay indoors.

What the shock wave in the video shows

Watch the sky just after the first blast. A pale, expanding ring sweeps outward from the crater, pushing down the ash on the volcano's slopes and lifting the clouds above it. This is a pressure wave from the explosion, travelling through the air at around the speed of sound. As it passes, the sudden change in pressure makes moisture in the air condense briefly, which is why the wave becomes visible at all.

Light reaches the camera almost instantly, but sound in air travels at roughly 340 metres per second. The gap of about 13 seconds between seeing the blast and hearing the boom therefore puts the boat roughly four to five kilometres from the vent. When the wave arrives, the microphone records it as a single sharp bang.

Visiting a living volcano safely

Australian Geographic described the 2014 event as a relatively small eruption, yet it still produced a towering ash cloud. Check the latest advice from the Rabaul Volcano Observatory before visiting: activity at Tavurvur can change quickly, and the 2014 eruption led to evacuations within hours.

For a very different volcanic landscape, read our Tongariro feature, or see a dramatic sky of another kind in the lightning-warning photograph explainer.

Related reading:

• Tolbachik in Photographs: Andrew and Luda’s Volcanic Landscapes
• Thirteen Crater-Lake Landscapes: Calderas, Volcanic Craters and an Impact
• Eyjafjallajökull in Time-Lapse: Sean Stiegemeier’s May 2010 Film

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