The geography of Indonesia is dominated by volcanoes that are formed due to subduction zones between the Eurasian plate and the Indo-Australian plate. Some of the volcanoes are notable for their eruptions, for instance, Krakatau for its global effects in 1883, Lake Toba for its supervolcanic eruption estimated to have occurred 74,000 Before Present which was responsible for six years of volcanic winter, and Mount Tambora for the most violent eruption in recorded history in 1815.
Halmahera island in the north of Molucca archipelago has been formed by the movement of three tectonic plates resulting in two intersecting mountain ranges, which form four rocky peninsulas separated by three deep bays. A volcanic arc stretches from north to south in the west side of Halmahera, some of which are volcanic islands, for instance, Gamalama and Tidore.
Gamalama's island name is Ternate and it has been the center for spice trading since the Portuguese Empire opened a fort in 1512. Due to its location as the center for spice trading during the Age of Discovery, historical records of volcanic eruptions in Halmahera have been available as far back as the early sixteenth century.