At this point I must confess that I am skeptical of this claim. These marks are just too much like many, many other marks in the caves that are not being identified as volcanic eruptions. As I said above, a volcanic eruption is such an impressive event that we should expect to see it recorded in the art of the people who witnessed it. Personally, I just cannot quite go along with this being such a record.
If you are interested in more detail please refer to the article in PLOS, cited below.