1. Volcanoes
Forms when magma reaches the Earths surface and erupts as lava or ash

2. Volcano Formation -Melting occurs in asthenosphere
-Magma is lava underground
-Magma is less dense than surrounding rock
-rises to lithosphere and creates cracks in the solid rock
-cracks are how magma reaches surface

3. Plate Boundaries
Eruptions on plate boundaries that separate, collide, or are hot spots

4. Convergent Plate Boundaries
-most volcanoes are at plate boundaries around the Pacific at subduction zones - this is the Ring of Fire

5. Divergent Plate Boundaries
Mostly unnoticed b/c they
occur under water
- One major divergent boundary that is above water is the East African Rift Valley

6. Hot Spots Balloon like plume Usually NOT near plate boundaries
Stationary (non moving)
Creates island chains in the ocean (Hawaii)

7. Lava -Magma that has reached the surface
Viscosity -measure of a fluids RESISTANCE to flow - low viscosity flows more easily (water) than high viscosity (molasses) - viscosity decreases as temp increases

8. Chemical Composition Mafic Lava - low viscosity
- Heavier elements (magnesium
and iron)
- Usually quiet eruptions
Felsic Lava
- High viscosity
-Lighter elements (silicon, oxygen, aluminum, potassium)
- Explosive eruptions

9. Volcanoes are classified by their size, shape, and mineral type
Types of Volcanos
Volcanoes are classified by their size, shape, and mineral type
Composite Cone
- form at convergent boundaries
- explosive eruptions
- large, steep shape 1000’s of meters wide
- composed of ash and lava
- pyroclastic flows- a fast-moving current of hot gas and rock

10. Shield Cone -fluid lava erupts, travels far - broad, wide, flat shape - gas poor -composed of lava -quiet eruption
Cinder Cone
-high temp
- gas rich
- mafic
-explosive, ejects cinders
-smaller 100’s meter range
- short eruption cycles
- composed of ash