Geologic Summary

On the premise of geomorphology theory, Rinjani is one of the series of volcanoes built in the Lesser sunda islands because of the subduction of Indo-Australian oceanic crust beneath the Lesser archipelago, and it’s taken that the source of melted magma is concerning 165–200 kilometres (103–124 mi) depth.

The earth science and tectonic setting of Lombok (and nearby Sumbawa) are described as being in the central portion of the Sunda Arc.The oldest exposed rocks square measure miocene, suggesting that geologic process and geological phenomenon began significantly later than in Java and Sumatra to the west, where there square measure abundant volcanic and intrusive rocks of late geological era age. The islands are placed on the eastern edge of the Sunda shelf, in an exceedingly zone wherever crustal thickness is apparently speedily decreasing, from west to east

The seismic velocity structure of the crust during this region is transitional between typical oceanic and continental profiles and therefore the Mohorovičić separation (Moho) appears to lie at concerning 20 kilometres (12 mi) depth.These factors tend to suggest that there has been restricted chance for crustal contamination of magmas erupted on the islands of Lombok and Sumbawa. additionally, these islands deceive the west of these elements of the eastern-most Sunda and west Banda arcs wherever collision with the Australian plate is outwardly progressing.

The volcano of Rinjani is 165 to 188 kilometres (103–118 mi) higher than the Benioff Zone.There is a marked offset within the line of active volcanoes between the foremost easterly Sumbawa volcano (Sangeang Api) and therefore the line of active volcanoes in Flores. this implies that a serious transcurrent fault cut across the arc between Sumbawa Island and Flores. this is considered to be a feature representing a serious tectonic discontinuity between the east and west Sunda Arcs (the Sumba Fracture).Further, a marked absence of shallow and intermediate earthquake activity within the region to the south of Lombok and Sumbawa is a feature interpreted to represent a marked break within the Sunda Arc Zone. Faulting and folding caused strong deformation within the eastern a part of Lombok Basin and is characterised by block faulting, shale diapirs and mud volcano.