1. VOLCANOES!

2. Factors Affecting Eruptions
Magma temperature
Hotter flows easier…
Magma viscosity – determined by temp and composition. High silica = high viscosity (thickness)
High viscosity = violent eruptions…
Dissolved gases
More gasses means more violent eruptions…

3. Volcanic Materials- Lava
3 TYPES OF LAVA FLOWS
Aa- rough and jagged
2) Pahoehoe - wrinkly and ropey texture
3) Pillow - forms underwater at boundaries

4. Aa Pahoehoe Pillow

5. Volcanic Materials- Gases
Water Vapor, Carbon Dioxide, Nitrogen, Sulfur Dioxide, and Chlorine
Kilauea Volcano, Hawai`i From emitted 1,000-2,000 metric tons of SO2 every day!

6. Volcanic Materials Pyroclastic Materials = Ejected fragments
Ash – fine material
Cinders and lapilli = medium/pebble sized
Bombs and blocks (big stuff) block = hard, bombs = lava

7. Ash Bombs & Blocks
Cinders

8. Volcanic Terms Crater – steep walled depression at top
Caldera – large depression in a volcano due to collapse of volcano

9. Volcanic Terms
Conduit – pipe connecting magma chamber to the surface Vent – top of the conduit

10. Volcanic Terms Lava plateau – raised flat area of lava
Volcanic neck – remnant of eroded volcano

11. Columbia Lava Plateau- covers parts of Washington, Oregon, and Idaho

12. Composite Cinder Cone Shield
Types of Volcanoes
Composite
Cinder Cone
Shield

13. Shield Volcanoes broad base with gently sloping sides
Huge in size, mild eruptions, mostly flows,
ex: Hawaii
Mauna Kea, Hawaii

14. Cinder Cone Narrow base and steep sides
-Small, violent for size, pyroclastic eruptions, ex: Mt. Paricutin, Sunset crater in AZ

15. Composite Cone
Medium base and moderately sloped size (volcano looking)
Medium size, violent eruptions, andesitic lava, combination of flows and pyroclastic eruptions, ex: Mt. St. Helens

16. Mt. St. Helens Before & After

17. Igneous Activity Plutons (intrusive igneous bodies)
Classified by shape, size, and relationship to surrounding rock layers
Sill – horizontal and between rock layers
Dike – vertical and cut across rock layers
Laccolith – dome/mushroom shaped plutons
Batholith – more than 100 km2 of exposed rock
Stock – less than 100 km2 of exposed rock

18. Volcano Dangers
Pyroclastic flows – hot gases, glowing ash, and larger rock fragments
Very hot (like cook your butt hot)
Can attain 200 km/hr
Lahars – mudflow formed from volcanic ash and water (melted snow or rain)
Eruptions – you’re there one minute and gone the next…can you say vaporized

19. Origin of Magma Read pages 291 – 292 The role of heat
The role of pressure
The role of water

20. Volcano Locations Convergent plates Divergent plates
Subducting plate melts and magma rises
Japan and Mt St Helens
Divergent plates
Plate diverge and magma rises through the rift
Mid-ocean ridge
Iceland
East African Rift
Intraplate (hot spots)
Mantle plume rises towards the surface
Hawaii and Yellowstone