Geoscientist Online

This volume presents a fairly comprehensive account of the geology and ecology of Lake Pavin, in the Auvergne Mountains of the French Massif Central.  The lake marks the site of the region's last eruption some 7,000 years ago.  Originally formed as a volcanic maar with a lake over 100 m deep, the height of the lake’s only outlet was then reduced several times.  Typically, lake surface waters do not mix with those at depth, which remain isolated or meromictic with some seasonal exchange – processes ably demonstrated in a chapter on the carbon cycle that includes the water balance within the lake, with deep mineral springs at depths of 53 and 68 m. 

Following the 1986 Lake Nyos degassing disaster in Cameroon, when this maar-lake emitted a blanket of heavier-than-air carbon dioxide that flowed down the local valley for over 20 km killing at least 1,700 people, research into such events significantly increased.  The second chapter looks into possible historical degassing events at Lake Pavin.  I remain rather unconvinced, however, when evidence for the 1936 event relies on one witness fifty years later.  It would have been interesting to consider the future faint possibility of crustal relaxation, followed by intrusion and near-surface degassing of magmatic dykes beneath these post glacial maars.

A brief chapter on the Monts Dore caldera sets the scene for the geological chapters.  Another outlines two centuries of debate and controversy, followed by a chapter on the phreatomagmatic deposits themselves.   This excellent account is blighted by poorly reproduced figures, which often appear in pallid pastel tones.  Geographical coordinates, either in the margins or text, are not given for some truly innovative geophysical sections and photographs of freshly excavated faces.   While the English is better than in many chapters, Fig. 6.2 with "actualized traduction" for the word translation within the caption sums up the failure of not employing native speakers to improve the text, which is often full of French syntax.

The magmatic evolution of the four southernmost Chaîne des Puys volcanoes is detailed before another chapter considers the distribution of ashes from these eruptions over the surrounding countryside.  The geomorphology of the lake and surrounding area is discussed without nearly enough space for the figures.   A chapter on farmed fish populations and methods for estimating catches, precedes two final chapters on sedimentology and paleolimnology.   The former reproduces multi-beam bathymetry and bottom profiles alongside sampled gravity cores, while the latter uses deeper cores to reconstruct the maar when it was 13 m higher, before a catastrophic lake outburst some 1,400 years ago.