The auxiliary material contains three videos. The videos highlight the differences between Type 1 and Type 2 explosions. All videos were recorded using a Sony HDR-SR7 at a distance of ~1 km to the north of the vent. The difference in vent locations is clear from the daytime videos (S1 and S3) as is the differenence in duration. These examples of Type 2 events are much more impulsive than the Type 1 event. While bombs can be seen in S3, they are much more obvious in S2. No bombs are visible in the Type 1 explosion video, S1.

Video S1. A typical Type 1 event from January 2008.

Video S2. A night video of a Type 2 explosion from January 2009. This video was recorded using the "night mode" near-infrared-sensitiveeee setting.

Video S3. A typical Type 2 event from January 2009.