The Eyjafjallajökull volcano in Iceland begins to erupt on December 19, 1821, causing some damage.
Notably, the ash released from the eruption contains a large fraction of fluoride, which in high doses may harm the bone structure of cattle, horses, sheep and humans.
The eruption also causes some small and medium glacier runs and flooding in nearby rivers Markarfljót and Holtsá.
The eruptive phase starts on December 19 and 20 by a series of explosive eruptions and continues over the next several days.
The sources describe heavy ash fall in the area around the volcano, especially to the south and west.
The sequence of eruptions will continues on a more subdued level until June 1822.
