1. Earth Science Notes Volcano Types

2. Factors Affecting Eruptions
Trapped Gases
Carbon dioxide and water vapor get trapped in magma and escape when pressure decreases
Gases that build up a lot of pressure cause explosive eruptions

3. Factors Affecting Eruptions
Silica
Silica is a compound composed of silicon and oxygen
Magma that is silica-rich is produces explosive eruptions
Granitic magma
Found at subduction zones
Lava is more runny in consistency
Magma that is silica-poor produces quiet explosions
Basaltic magma
Found at hotspots
Lava is thicker more viscous in consistency

4. Forms of Volcanoes Shield Volcanoes
Forms from the build up of quiet eruptions through vents or fissures
Resembles a warriors shield
Has gently sloping sides
Basaltic lava flows from here

5. Shield Volcanoes

6. Shield Volcanoes

7. Forms of Volcanoes Cinder Cone Volcanoes
Forms from the build up of explosive eruptions
Bits of rock called tephra are blown into the air and fall to the ground. Over time the sides of this volcano forms
Resembles a giant cone
Very steep side with loosely packed stone

8. Cinder Cone Volcanoes

9. Cinder Cone Volcanoes

10. Forms of Volcanoes Composite Volcanoes
Intermediate between cinder cone and shield volcanoes
Eruptions vary some may be explosive others quiet
Alternating layers of tephra and lava form the sides of the volcano
Found near subduction zones

11. Composite Volcanoes
                                 composite volcano

12. Composite Volcanoes

13. Composite Volcanoes

14. Forms of Volcanoes

16. More Volcano Types

17. Features Of Volcanic Activity
Batholiths – formed when magma cools underground

18. Features Of Volcanic Activity
Volcanic Neck – magma inside volcano cools and outside is eroded away

19. Features Of Volcanic Activity
Dike – magma that cools in vertical cracks

20. Features Of Volcanic Activity
Sill – magma that cools in horizontal cracks

21. Features Of Volcanic Activity
Caldera – top of volcano collapses on emptied magma chamber
                                                    
Photograph by M. Williams, National Park Service, 1977

22. Features Of Volcanic Activity

23. Volcanoes Destructiveness
Mount Vesuvius AD

24. Volcanoes Destructiveness
Mount St. Helen - Washington

25. Volcanoes Destructiveness

26. Volcanoes Destructiveness
A super-eruption has the potential to cover the United States in 3 feet of ash from a plume. Pyroclastic flow would engulf the greater part of three states, and there is evidence that the last major 'super' eruption plunged the world into a freezing, volcanic winter that lasted a decade. An eruption would devastate world agriculture, severely effect the distribution of food and cause mass famine.
This Diagram shows range of potential destruction

27. After the Aftermath

28. Summary Volcano Types Features of Volcanic Activity
Shield / cinder cone / composite / others
Features of Volcanic Activity
Intrusive Igneous Rocks (CH 5)
Destructiveness of Volcanoes
The Circle of Life