The Mariana Islands are located in the western Pacific Ocean. They form an arc of volcanic island from Guam in the south to the island of Farallon de Pajaros in the North.
The Mariana Arc is one of the best examples of an intraoceanic island arc. Historic eruptions and frequent reports of discolored water indicate that submarine volcanoes are active throughout the arc. There are 42 submarine volcanoes in the mariana Islands.
Anatahan has been the most active volcano in the group in recent years.