Two Small Volcanoes, One Inside the Other: Geophysical and Drilling Investigation of Bažina Maar in Western Eger Rift

Abstract Maar‐diatreme volcanoes are small volcanic structures with a funnel‐shaped crater surrounded by tephra‐ring. They usually formed the explosive phreatomagmatic eruptions when groundwater comes into contact magma. We focus on such structure in geodynamically active western Eger Rift (Czech Republic) and present results from multidisciplinary geophysical investigation calibrated drilling newly discovered Pleistocene Bažina maar. evaluated morphological (LiDAR‐based DEM) data confirmed existence of maar‐diatreme combined methods. In map view, they revealed circular negative gravity anomaly, funnel‐shape low‐resistivity strong magnetic anomaly. These allowed for optimal location two boreholes maar crater, which evinced its country rocks lithologies filling. The coherent volcaniclastic deposits, moreover, it presence pyroclastic cone olivine nephelinite feeding conduit. Further investigations disclosed subsequent cone(s) several generations systematic decrease water influence eruption style. Different styles suggest unique evolution volcanoes, one inside other. age eruption, estimated reverse polarity detected implies that effusion solidification lava during must be older than 0.78 Ma (Pleistocene). This points to an volcanism span ∼0.5 Ma, where represents oldest (maybe opening) phase.