These are examples of small explosions in Shishaldin's crater that have been recorded at station SSBA. Each explosion shows up as a low-frequency seismic wave that travels through the ground, followed by a high-frequency airwave pulse. The airwaves arrive later because energy from the explosion travels more slowly through the air than it does through the ground.
Image courtesy of the AVO/UAF-GI.
Please cite the photographer and the Alaska Volcano Observatory / University of Alaska Fairbanks, Geophysical Institute when using this image.
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