A maar is a round crater caused by a phreatomagmatic eruption, often filled with water. Ichi-no-Me gata, Ni-no-Me gata, and San-no-Me gata are famous and representative maars in Japan. Ichi-no-Me gata is known worldwide since its ejecta include substances from the great depths of the Earth. What lays just in front of this explanatory plaque is Ni-no-Me gata, 400 meters in diameter and 11.8 meters deep. Ichi-no-Me gata is 600 meters in diameter and 44.6 meters deep. San-no-Me gata (which is not visible from here) is 400 meters in diameter and 31.0 meters deep.