Abstract This paper presents documentary evidence suggesting that the most recent volcanic activity in Germany may have occurred just over 200 years ago, rather than the 11 000 years held currently (Ulmener Maar, West Eifel). Several descriptions recounted here suggest that a mountain in Germany, the Gleichberg, may have erupted in the early summer of 1783. The reports of the volcanic event are laden with detail that would tempt the reader to accept them as genuine descriptions of an eruption, had the event been located in an historically active volcanic region. However, there are several reasons to suggest that the report of the Gleichberg eruption was a complex hoax, written to exploit the fear and panic generated by the dry fog present over much of Europe at the same time, which had its origins in the Laki fissure eruption. Geologically, the Gleichberg forms part of the Grabfeld, and is of Tertiary volcanic origin. There are no compelling geological reasons to suggest that this area has been tectonically active in recent times. The convincing detail of the report is used to illustrate the pitfalls waiting for geologists, historians and archaeologists who are using historical documents and folklore to explore the impact of volcanic eruptions upon ancient peoples and environments; time may lend weight to documents and folklore, which in reality may deserve none.