1808/1809 Mystery Eruption

Records from the time throughout the world were checked but nothing appeared viable until the summer of 2014, when PhD student Alvaro Guevara-Murua and Dr Caroline Williams of the University of Bristol discovered an account of atmospheric events consistent with such an event by Colombian scientist Francisco José de Caldas. Apart from the occasional sighting by European explorers, most of the reporting on volcanic activity, such as that in the Rabaul area, which has had VEI 6 eruptions, went back only to the mid-19th century. It is known that the Chilean Putana volcano also had a major eruption around this time with an approximate date of 1810 (with a 10-year margin of error).

Source: en.wikipedia.org