Lava composition Volcano

sarychev peak eruption, matua island, oblique satellite view



melting of subducted slab containing sediments
magma mixing between felsic rhyolitic , mafic basaltic magmas in intermediate reservoir prior emplacement or lava flow.




if erupted magma contains <52% , >45% silica, lava called mafic (because contains higher percentages of magnesium (mg) , iron (fe)) or basaltic. these lavas less viscous rhyolitic lavas, depending on eruption temperature; tend hotter felsic lavas. mafic lavas occur in wide range of settings:

at mid-ocean ridges, 2 oceanic plates pulling apart, basaltic lava erupts pillows fill gap;
shield volcanoes (e.g. hawaiian islands, including mauna loa , kilauea), on both oceanic , continental crust;
as continental flood basalts.


some erupted magmas contain <=45% silica , produce ultramafic lava. ultramafic flows, known komatiites, rare; indeed, few have been erupted @ earth s surface since proterozoic, when planet s heat flow higher. (or were) hottest lavas, , more fluid common mafic lavas.