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Goldschmidt 2007 Excursion: The Laacher See Volcano

G. Wörner, Göttingen

 

This one-day excursion on 25 August 2007, was attended by 40 geoscientists from 14 countries and concentrated on the origin of the Laacher See tephra deposits.

The Laacher See volcano is part of the Quaternary East Eifel volcanic field of western Germany and located in a belt of Upper Tertiary to Holocene volcanism in Central Europe. The Eifel is underlain by a region of anomalously hot mantle and is characterized by intraplate alkaline volcanism (basanites, tephrites, phonolites, leucitites and nephelinites. The Laacher See volcano is the most recent centre in the East Eifel (13.065 ± 50 ybp, Fig. 1) erupted 6.3km3 of phonolitic magma during period of a few days approximately 12,880 years ago. The Laacher See Tephra exhibits a vertical zonation in its petrography and major and trace element chemistry and has been inferred torepresents the inverted zoned magma chamber (Fig. 2).

The group visited one of the most famous outcrops of Laacher See Tephra : the Wingertsberg quarry c. 1 km south of the crater rim. A collection of pumice clasts demonstrated the compositional variation and erupted xenoliths were used to reconstruct the magma chamber margins (contact metamorphosed Devonian slates from about 3 to 6 km depth).

We also visited the Laacher See Abbey, one of the most beautiful Roman churches north of the Alps.

A leisurely walk along the lake shore led us to exposures along the inner crater wall (Devonian slate and Quaternary lavas and scoria deposits), gave an impression of the size and natural beauty of the crater and its lake. Finally we were able to observe (and smell) volcanic gases, which continue to emanate along the lake shore (Fig. 3).

A visit to the Laacher See volcano is incomplete without descending down a stair case tunnel ( <120 steps) to the ancient underground excavations of the Mendig lava flow (a tephrite), which were used for the production of millstones since Roman times. More recently, the cellars were utilized by breweries, one of which still produces a delicious "Volcano Beer". The day ended cheerfully with beers and food in the patio of the brewery.