My favorite unexpected consequence:

9. THE ERUPTION MAY HAVE LED TO MORMONISM.

One of the more unusual effects of the temporary climate change brought about by Mount Tambora’s eruption is that it may have indirectly led to the creation of the Mormon religion. Mormon founder Joseph Smith’s family was one of thousands that left Vermont during the freakishly cold summer of 1816. The Smith family subsequently settled in New York, where a teenage Joseph would go on to experience the events that led to his publication of the Book of Mormon. https://www.mentalfloss.com/article/73585/15-facts-about-yea...