Morphology of the Youngest Little Volcanoes in Western Bohemian Massif

Abstract

The two little volcanoes, Komorní hůrka and Železná hůrka , are the youngest volcanoes in the western part of the Bohemian Massif, the principal regional geological unit of the Central Europe. The two volcanoes do not impress by their height, or complex petrological composition, but rather by their age uniqueness, as the dating results vary between 100,000 and 450,000 years. There are numerous other Cenozoic volcanoes in the western part of the Bohemian Massif, but they range between 31 and 8 million years. From this perspective, the two youngest ones prove that after certain break in volcanic activity since 8 million years ago, a new phase of “recent” volcanism has occured. Nowadays, we can still observe some ongoing signs of magmatic activity, e.g. many sites with intensive CO₂ degassing, mofettes , hot and cold mineral water springs including a small hot geysir , and relatively significant earthquake swarms with frequent repetition and magnitudes up to M4.5 in the nearby region of the Cheb Basin and surroundings. The little volcanoes were, anyway, a subject of investigation for centuries. The most famous is the research performed by J.W. Goethe , a worldwide known poet and scientist. We have, moreover, recently discovered the only Quaternary maar in the Bohemian Massif by geophysical surveying in the near vicinity of Železná hůrka.