Anatahan Island is situated about 120 km north of Saipan - the capital of the Commonwealth of the Northern Mariana Islands. It lies at the southern end of the 1500-km-long Izu-Bonin- Mariana arc.
The island of Anatahan is only 1% of the volume of the entire volcano, which is 3700 m high from submarine base to summit, and an average diameter of 35 km. The highest point on the island is immediately west of the caldera.
Anatahan Island measures 9 km (east–west) by 3.7 km (north–south). The summit of the island contains an elongate caldera, 5 km by 2 km. The caldera is approximately 10 sq km in size and occupies about a third of the island’s area.
The east crater is located in the eastern part of the caldera. It is a a pit crater 1.4 km by 1.2 km in diameter, and 200 m deep.