13. Fuji Kao Mayan

16. Bali

18. Pinatubo

22. Cinder Cones Stratovolcanoes Fountains: shields and plateaus Domes Gas Content Viscosity

24. Classification of Igneous Rocks Figure 2-5. Classification of the pyroclastic rocks. a. Based on type of material. After Pettijohn (1975) Sedimentary Rocks, Harper & Row, and Schmid (1981) Geology, 9, 40-43. b. Based on the size of the material. After Fisher (1966) Earth Sci. Rev., 1, 287-298.

27. Wt. % oxides Wt. % SiO 2 45 75 FeO, MgO, CaO Na 2 O, K 2 O H2OH2O

28. Water content (wt. %) Composition Basalt Andesite Rhyolite Water Saturation Exsolution of a vapor of a magma

29. Fractional Crystallization Basalt Andesite Rhyolite low H 2 O Explosive volcanism 50 % SiO 2 75% SiO 2 ? Water content of a rhyolitic magma ????

33. Mt. St. Helens

34. Granites

37. Origin of Andesites Fractional crystallization of basaltic magma Contamination of basaltic magma by continental crust Both of the above Partial melting of “special (wet ?) manlte”

39. Origin of Granite/ Rhyolite Fractional crystallization of basaltic magma ( volume problem for some areas) Partial melting of continental crust