'Laacher See' or 'Laach Lake' (in English) is a
crater lake or more exactly a
caldera lake in the
Rhineland-Palatinate,
Germany, situated close to the cities of
Koblenz,
Mayen (11 km), and
Andernach (14 km). It fills a volcanic
caldera in the
Eifel mountain range, the only caldera in Central Europe. It is part of the area of the "east Eifel
volcanic field".
The great Eifel lake takes its name from the
Old High German word "lacha" which in turn is derived from
Latin "lacus" as English "lake". Thus the name literally means "Lake of the Lake" similar to the "
Loch Lochy" in the
Scottish Highlands with the same meaning.
The lake lies above sea level, in circumference, and surrounded by a ring of high hills. The water has a blue colour, very cold and bitter to the taste. The lake has no natural outlet and so the water level changes considerably due to evaporation and rainfall conditions. On the western side lies the
Benedictine monastery of
Maria Laach Abbey (''Abbatia Lacensis''), founded in
1093 by
Henry II of Laach of the
House of Luxembourg, first ''
count palatine of the Rhine'' who has had his castle opposite to the monastery above the eastern lakeside.
The caldera was formed after the Laacher volcano erupted, between 12,900 and 11,200 years ago. The remaining crust collapsed into the empty magma chamber below, only two or three days after the eruption.
[1] This eruption was 250 times larger than the eruption of
Mount St. Helens in 1980. Remains of this eruption can be found all over Europe and is often used for dating of sediments. A number of unique
minerals can be found in the region,
[2] and
quaries to mine the stone as a
building material.
The Laacher is still considered to be an active volcano, proven by seismic activities and heavy thermal anomalies under the lake. Carbon dioxide (CO
2) gas from magma still bubbles up at the southeastern shore,
[3] and scientists believe that a new eruption can happen at any time, which, today, would be a disaster beyond all description.

Panorama
References
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★
"Lake Formation and Catastrophic Dam Burst during the Late Pleistocene Laacher See Eruption (Germany)" - ''Naturwissenschaften''
1. "Assembly area: Laacher lake" - translation
2. "Structure and Dynamics of the Laacher See Magma Chamber (Eifel, Germany)…" - ''Journal of Petrology'' website
3. ''National Geographic''. 1986 #9