EIFEL, a district of Germany, between the Rhine, the Moselle and the frontier of Luxemburg. It is a hilly region, most elevated in the eastern part (Hobe Eifel), where there are several points above 2,00o ft. above sea-level. In the west is the Schnei fels; and the southern part, where the most picturesque scenery and chief geological interest is found is called the Vorder Eifel.
The Eifel is an ancient massif of folded Devonian rocks and upon its margins, near Hillesheim and towards Bitburg and Trier, Triassic sandstones, marls and limestones rest unconformably. On the southern border, at Wittlich, terrestrial deposits of the Permian Rothliegende also occur. Lower Devonian slates and sandstones form the greater part of the region ; but folded amongst these, in troughs running from south-west to north-east lie the Middle Devonian fossiliferous limestones, and occasionally, e.g., near Budesheim, small patches of Upper Devonian. Upon these peneplaned Devonian strata stand numerous small volcanic cones of Tertiary age, many of which, though now extinct, are still very perfect in form. Emission of carbon dioxide and heated waters still occurs in many places. The eruptions probably ceased in Quaternary times for the Iavas of Papenkaule are clearly posterior to the excavation of the valley of the Kyll, and a lava flow has forced the Uess to seek a new course. The volcanic rocks occur both as tuffs and as lava-flows. They are chiefly leucite and nepheline rocks, such as leucitite, leucitophyre and nephelinite, but basalt and trachyte also occur. The leucite lavas of Nieder mendig contain hailyne in abundance. The most extensive and continuous area of volcanic rocks is that surrounding Laacher See and extending eastwards to Neuwied and Coblenz and even beyond the Rhine.
The numerous so-called crater-lakes or maare present several features of interest. They do not, as a rule, lie in true craters at the summit of cones, but rather in hollows formed by explo sions. The most remarkable group is that of Daun, where the three depressions of Gemund, Weinfeld and Schalkenmehren have been hollowed out in Lower Devonian strata. The first of these shows no sign of either lavas or scoriae, but volcanic rocks occur on the margins of the other two. The two largest lakes in the Eifel region, however, are Laacher See and Pulvermaar.