The island slopes up from the shores of the deep seas surrounding the island to a high, mostly non-volcanic, mountainous interior.
Active volcanoes are found in the northern Minahassa Peninsula, stretching north to the Sangihe Islands.
The northern peninsula contains several active volcanoes such as Mount Lokon, Mount Awu, Soputan and Karangetang.

According to plate reconstructions, the island is believed to have been formed by the collision of terranes from the Asian Plate (forming the west and southwest) and from the Australian Plate (forming the southeast and Banggai), with island arcs previously in the Pacific (forming the north and east peninsulas).
Because of its several tectonic origins, various faults scar the land and as a result the island is prone to earthquakes.

Sulawesi, in contrast to most of the other islands in the biogeographical region of Wallacea, is not truly oceanic, but a composite island at the centre of the Asia-Australia collision zone.
Parts of the island were formerly attached to either the Asian or Australian continental margin and became separated from these areas by vicariant processes.
 In the west, the opening of the Makassar Strait separated West Sulawesi from Sundaland in the Eocene c. 45 Mya.
 In the east, the traditional view of collisions of multiple micro-continental fragments sliced from New Guinea with an active volcanic margin in West Sulawesi at different times since the Early Miocene c. 20 Mya has recently been replaced by the hypothesis that extensional fragmentation has followed a single Miocene collision of West Sulawesi with the Sula Spur, the western end of an ancient folded belt of Variscan origin in the Late Paleozoic.
The island slopes up from the shores of the deep seas surrounding the island to a high, mostly non-volcanic, mountainous interior. Active volcanoes are found in the northern Minahassa Peninsula, stretching north to the Sangihe Islands. The northern peninsula contains several active volcanoes such as Mount Lokon, Mount Awu, Soputan and Karangetang.
According to plate reconstructions, the island is believed to have been formed by the collision of terranes from the Asian Plate (forming the west and southwest) and from the Australian Plate (forming the southeast and Banggai), with island arcs previously in the Pacific (forming the north and east peninsulas). Because of its several tectonic origins, various faults scar the land and as a result the island is prone to earthquakes.
Sulawesi, in contrast to most of the other islands in the biogeographical region of Wallacea, is not truly oceanic, but a composite island at the centre of the Asia-Australia collision zone. Parts of the island were formerly attached to either the Asian or Australian continental margin and became separated from these areas by vicariant processes.  In the west, the opening of the Makassar Strait separated West Sulawesi from Sundaland in the Eocene c. 45 Mya.  In the east, the traditional view of collisions of multiple micro-continental fragments sliced from New Guinea with an active volcanic margin in West Sulawesi at different times since the Early Miocene c. 20 Mya has recently been replaced by the hypothesis that extensional fragmentation has followed a single Miocene collision of West Sulawesi with the Sula Spur, the western end of an ancient folded belt of Variscan origin in the Late Paleozoic.
Sulawesi