The volcano of Rinjani is above the Benioff Zone. There is a marked offset in the line of active volcanoes between the most easterly Sumbawa volcano (Sangeang Api) and the line of active volcanoes in Flores. This suggests that a major transcurrent fault cut across the arc between Sumbawa Island and Flores. This is considered to be a feature representing a major tectonic discontinuity between the east and west Sunda Arcs (the Sumba Fracture). Further, a marked absence of shallow and intermediate earthquake activity in the region to the south of Lombok and Sumbawa is a feature interpreted to represent a marked break in the Sunda Arc Zone. Faulting and folding caused strong deformation in the eastern part of Lombok Basin and is characterized by block faulting, shale diapirs and mud volcano.