The caldera was formed after the colossal Laacher See eruption dated  to 12,900 years ago. The remaining crust collapsed into the empty  magma chamber below, probably two or three days after the eruption.  An estimated 6 km³ of magma was erupted, producing around 16 km³  of tephra. This massive eruption thus had a Volcanic Explosivity Index  (VEI) of 6, and was larger than the colossal 1991 eruption of Mount  Pinatubo (Philippines) which also had a VEI of 6 (10 km³ of tephra  erupted). Tephra deposits from the eruption dammed the Rhine,  creating a 140 km2 (50 sq mi) lake. When the dam broke, an outburst  flood swept downstream, leaving deposits as far away as Bonn. The  Laacher See is a potentially active volcano, proven by seismic activities  and heavy thermal anomalies under the lake. carbon dioxide gas from  magma still bubbles up at the southeastern shore.  Eifel Laacher See Location: 50.24 ° N, 7.16° E Elevation: 274 m Photo: Rolf Cosar Photo: Rolf Cosar Geologisches Blockbild der Gegend um den Laacher See (W.MEYER) 6. Nov. 2003 HOME Google Earth