Sofugan is a steep vertical pinnacle that rises 99 m above the sea surface south of Tori-shima volcano. Its dramatic shape gave it its nickname "Lot's Wife Rocks." In 1975, discolored sea water was observed about 500 m north of Sofugan, and the volcano was reclassified as active by the Japan Meteorological Agency.

The basaltic-to-andesitic pinnacle is the remnant of a large eroded stratovolcano 28 km wide at its base and rising 2200 m above the sea floor. A submarine depression is located between the pinnacle and a curved submarine ridge to the SW rising to less than 150 m of the sea surface.