View across Schalkenmehren Maar towards Schalkenmehren, Eifel, Rhineland-Palatinate, Germany, Europe

Looking down into Ubehebe crater, a Maar volcano, caused by groundwater contacting hot magma or lava, Death Valley National Park, California, United States of America, North America

Looking down into Ubehebe crater, a Maar volcano, caused by groundwater contacting hot magma or lava, Death Valley National Park, California, United States of America, North America

Randecker Maar, former volcanic pipe, Ochsenwang, Swabian Alps, Baden-Wurttemberg, Germany, Europe

Zao, Miyagi, Japan

Aerial view of Windsborn crater lake, rural district of Daun, Eifel, Rhineland Palatinate, Gemany, Europe

Aerial view of Windsborn crater lake, rural district of Daun, Eifel, Rhineland Palatinate, Gemany, Europe

Angler in a boat on Meerfelder Maar, Eifel, Rhineland Palatinate, Germany

Ulmen with Ulmener Maar, Reflexion, Eifel, Rhineland-Palatinate, Germany, Europe

Gemundener Maar, Volcanic Eifel, Vulkaneifel, Schalkenmehren, Rhineland-Palatinate, Germany, Europe

Weinfelder Maar, also Totenmaar, maar lake in winter, Schalkenmehren, Daun, Volcanic Eifel, Rhineland-Palatinate, Germany, Europe

Maar and sedimentary rock of Ubehebe Crater, volcanic crater, Death Valley National Park, Mojave Desert, California, United States of America, USA