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Laacher See - the volcanic lake |
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 The volcanic eruptions in Germany were concentrated in a belt, about 600 km long, following the valley of the River Rhine, which occurred when a rift developed across Europe as the Atlantic Ocean opened. Most of the eruptions took place along major faults trending mainly from north to south or sometimes from northwest to southeast. Successive episodes of rifting were reflected in the activity that reached its climax in areas such as the Odenwald, Spessart, Taunus and Westerwald, Swabia and the Kaiserstuhl more than 15 million years ago.
It was only after a long interval that eruptions resumed in the Eifel
Mountains, which forms an extensive plateau, about 500 m high, in the
area between the River Rhine and its tributary the River Moselle. The
West Eifel zone, near Daun, runs for 50 km from northwest to southeast
in a band 20 km wide. The East Eifel zone, centred on the Laacher See,
near Mayen, is an area with some 50 vents that stretches 35 km from the
River Rhine in a belt about 25 km broad. The West Eifel Mountains has
long been famous for its maars, the circular lakes reaching up to more
than 2 km in diameter, for which the region has become the type
locality. But these beautiful relics of hydro volcanic eruptions are
also accompanied by tuff rings and many cinder cones, lava flows amd
domes, as well as extensive blankets of pumice have been widely
quarried, whereas the older materials have weathered to provide a
mixture of rich arable and meadow lands and woods surrounding
prosperous rural towns.
Volcanic activity began in the Eifel region about 800 000 years ago and
reached its distinct late climax between about 12 000 and 10 000 years
ago. It was also some 11 000 years ago that the great eruptions of
Laacher See distributed indicator beds as far a field as Switzerland,
northern Italy and southern Sweden (Bogaard & Schmincke 1985). One
or perhaps two magma reservoirs erupted alkaline basalts, basanites,
tephrites, phonolites and some trachytes. Basalts, tephrites and
basanites were responsible for most of the lava flows, cinder cones,
maars and tuff rings, whereas the domes and most of the layers of
pumice are chiefly phonolitic. Some domes and layers of tuff are also
composed of selbergite, a local phonolite rich in leucite. Although the
region has been quiet for several thousand years, emissions of carbon
dioxide from Laacher See, for instance, indicate that the magma
reservoir has cooled only to about 400°C.
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