1. Volcanoes
Gateways to the Underworld

2. Magma vs. Lava
Magma- Molten rock underneath Earth’s surface → Intrusive
Lava- Molten rock above Earth’s surface → Extrusive

3. Lava Flows The ability of lava to flow depends on its viscosity
The more viscous a substance is the slower it flows
Water has low viscosity
Honey has high viscosity
The more silica the lava contains the greater its viscosity

4. Types of Lava/Magma Basaltic: Andesitic Rhyolitic
Low viscosity, low gas, low silica
Andesitic
Medium viscosity, medium gas, medium silica
Rhyolitic
high viscosity, high gas, high silica

5. Comparison between lava flows
Highly Viscous Flow
-dome-like shape
-travels little distance
Andesitic flow
Viscous Flow
-thick flows
-travels some distance
Basaltic flow
Fluid Flow
-thin flows
-travels great distance

6. Where Do Volcanoes Occur?
80% convergent boundaries –Ring of Fire
15% divergent boundaries – Midocean Ridge
Hot Spots- Hot mantle rises toward Earth’s surface

7. Typical Volcano
Crater
Summit Vent
Flank Vent
Magma Chamber

8. Plutons Intrusive igneous rock bodies Cooled magma formations
Five different types
Can be exposed on Earth’s surface

9. Batholiths and Stocks Batholiths- largest plutons
Course-grained igneous rocks, km2
Stocks- Irregularly shaped plutons, smaller than batholiths.
Both cut across older rocks.

10. Laccoliths
Laccoliths: mushroom-shaped pluton with round top and flat bottom
Squeezes in between parallel layers of rock

11. Sills- flat pluton that squeezes in between parallel layers of rock
Sills and Dikes
Sills- flat pluton that squeezes in between parallel layers of rock
Dikes – cuts across pre-existing rocks by invading a cracks
Coarse-grained
What effects do you think these intrusions have on the surrounding rock?
Cm to 100s m thick
Coarse grained so how does that mean that they have cooled? Fast or slow?