I missed the other one as well which was a 3 second exposure. So, my mistake. (I thought for certain I didn't see anything with 30 seconds on it, but I think somewhere along the lines my brain filtered out the watermarks inappropriately, which I shouldn't have done.)

Although I'm still puzzled why some are getting caught up on the frame with a 30 second exposure. The image in question is clearly taken of a distant object, and the other exposures are reduced in exposure time by an order of magnitude.

Clearly, there was something occurring. Whether or not it was volcanic is another story entirely (or whether it was a collection of boats). The only use here though is to argue whether the differing exposure times was intentional in order to capture an image that differed from the actual event. But given the different exposure times, the alternative explanation is that he selected them based (at least in part) on proximity to the point of interest.