Bimodal volcanism of back-arc basin formation and in the products of both continental and oceanic hotspots (e.g. Yellowstone and the Canary Islands). Bimodal volcanism is normally explained as a result of partial melting of the crust, creating granitic magmas, during the emplacement of large volumes of relatively hot basaltic magma from a mantle source. The two magma types then form separate magma chambers giving rise to periodic eruption of both types of lava. Bimodal volcanism Bimodal volcanism is the eruption of both mafic and felsic lavas from a single volcanic centre with little or no lavas of intermediate composition. This type of
Ringing rocks of symmetry. The overall geometry is cylindrical, with an average diameter of one kilometer. The pluton consists of two major units: an inner core of quartz-bearing felsic units with a diameter of 600 meters and an outer mafic unit composed of coaxial concentric layers. In map view, the complex has a bulls-eye configuration. The outer zone of the pluton consists of two alternating mafic hybrid rock types. In chemical analysis the rocks are nearly identical; however, the early stage minerals, olivine and pyroxene, were preserved in one and not the other, giving the rocks sharply different weathering properties. The rock