Sumiyoshi-ike volcano refers to 2 maars 2 km apart located in the coastal lowland north of the Aira caldera: Sumiyoshi-ike (500 m diameter) and Yonemaru (1.2 km). The maars erupted when sea level was rising about 8,000 years ago (Sumiyoshi-ike) and 6500 years ago (Yonemaru). The larger of the two, Yonemaru, produced pyroclastic surges that traveled 4 km from the crater.