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
Lithology for the presence of calcite (or other forms of calcium carbonate) using dilute hydrochloric acid and looking for effervescence. The mineralogical composition of a rock is one of the major ways in which it is classified. In general, igneous rocks can be categorized by increasing silica content as ultramafic, mafic, intermediate, or felsic, though more mineral-specific classifications also exist. Likewise, metamorphic facies, which show the degree to which a rock has been exposed to heat and pressure and are therefore important in classifying metamorphic rocks, are determined by observing the mineral phases that are present in a sample. The colour