The Laacher See is a caldera in the Rhine Valley of Germany (see below). It is only ~30 km south of Bonn and ~60 km south of Koln (Cologne), just to the west of the Rhine River. It is part of the East Eiffel Volcanic Field and the 8-km wide caldera is currently filled with a lake. Now, most people don't think of volcanic activity occuring in central Europe, but it is believed that a mantle plume lies below this part of the continent, creating rifting and the volcanism in the Eifel Volcanoes. Laacher See last erupted ~12,900 years ago, but it was a doozy, erupting ~6 km3

The ash from the eruption can be found in the North Sea and throughout central Europe. Some of the deposits found near the caldera is remarkable, and (to me) seem so anomalous for the middle of the German countryside. There is some suggestion that the Laacher See eruption could have had a strong effect on the climate of Europe after the eruption and the human populations living there at the time. Although it has been quiet since the climactic eruption ~12,900 years ago, the caldera should still be considered potentially active as CO2 seeps exist in some parts of the lake, suggesting that there is still magma degassing under the lake. In fact, the CO2 can be a hazard, supposedly killing some Medieval monks in their sleep. There is no hazard map for Laacher See.