III Volcanoes - explosive, lava flows

A. Textures

1. lava
   1. pahoehoe (fig. 4.5a)
   2. aa (fig 4.5b)
   3. vesicular texture; cinders/scoria (fig. 3.5b)
   4. pillow lava (fig. 4.7)
2. explosive
   1. ash
   2. pyroclastic
   3. vesicular texture; pumice (fig. 3.17b)
3. obsididan
4. porphyritic texture

B. Controls on explosiveness

1. gas content (H₂O, CO₂, N, SO₂, H₂S)
2. magma viscosity)
   1. Temperature
   2. SiO₂ content

C. Types of volcanos (fig 4.13)

1. shield volcanos
2. cinder cones
3. composite volcanos
   1. lahars/pyroclastic flows
4. fissure eruptions
5. calderas

D. Distribution

1. spreading centers
2. subduction zones
3. hot spots