1. Do First Actions: Turn in Volcano vs Earthquake Webquest Questions:
What type of plate interaction(s) forms volcanos?
What type of plate interaction(s) does not form volcanos?
Boys rules still apply, hop up and get 30 minutes with me

2. Agenda Test is Wednesday: Plate Tectonics, Earthquakes, and Volcanos
Volcano Notes
Volcano Video

3. Pixar Video

4. What is a volcano?
A volcano is a rupture on the crust  that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface

5. Where do Volcanos occur?
Volcanos mostly occur at convergent and divergent plate boundaries
Plate motion causes mantle rocks to melt to form magma

6. What causes volcanoes?

7. Where do Volcanos occur?
Convergent boundaries produce volcanic arcs
At Ocean – ocean convergent boundaries rising magma can form volcanic arcs in an ocean (Aleutian Islands).
At Ocean – continental boundaries rising magma can form continental volcanic arcs (Andes Mountains).
75% of volcanos occur in the “Ring of Fire”
Divergent boundaries produce the greatest volume of volcanic rock along the oceanic ridge system

8. Where do Volcanos occur?
The remaining volcanos occur within a plate and not at a boundary which is called intraplate volcanism
The regions are known as “hot spots”
Volcanos occur here because a mass of hotter than normal mantle material called a mantle plume rises toward the surface.
The Pacific plate moves over a hot spot, producing the Hawaiian Islands.

9. Mantle Convection Models

10. Hot Spots

11. Types of Eruptions Violent (Explosive) Non-violent (Calm or Quiet)
Destroy the volcano
Viscous (thick) lava traps the gases until large pressures build up & the system explodes
Pyroclastic flow (ash, rock fragments) flow out of vent
Non-violent (Calm or Quiet)
Build up the volcano
Fluid lava flows easily allows gases to bubble away

12. Types of Lava
Lava is what magma is referred to once it reaches the surface
Viscous Lava (Thick)
Cool temperature
Composition: silica-rich (granitic)
Fluid Lava (Thin)
Higher temperatures
Composition: Low silica (basaltic)

13. Other Ejected Materials
Dissolved gases
Mainly water vapor and carbon dioxide
If gases escape easily then eruption is less explosive
Pyroclastic Materials
particles produced in volcanic eruptions
Range in size from very fine duct and volcanic ash (less than 2 millimeters) to pieces that weigh several tons

14. Pompeii After the 79 C.E. eruption

15. Parts of a Volcano
A volcano is a mountain formed of lava and/or pyroclastic material.
A crater is the depression at the summit of a volcano or that which is produced by a meteorite impact.
A conduit, or pipe, carries gas-rich magma to the surface.

16. Types of Volcanos
Shield volcano
Cinder cone volcano
Composite volcano

17. Types of Volcanos
The three main volcanic types are shield volcanoes, cinder cones, and composite cones.

18. Types of Volcanos Shield Volcanoes
Shield volcanoes are broad, gently sloping volcanoes built from fluid lavas.

19. Types of Volcanos Cinder Cones
Cinder cones are small volcanoes built primarily of pyroclastic material ejected from a single vent
Steep slope angle
Rather small in size
Frequently occur in groups

20. Types of Volcanos Composite Cones
Composite cones are volcanoes composed of both lava flows and pyroclastic material.
Large size
Alternating layers of lavas and pyroclastics
Most violent type of activity

21. Types of Volcanos
Volcanos can also be defined by when they are expected to erupt
Active: has erupted in the last 10,000 years
Dormant: hasn’t erupted in the last 10,000 years but it expected to erupt again
Extinct: hasn’t erupted in the last 10,000 years and is not expected to erupt again

22. Mount St. Helens Before and After the May 18, 1980, Eruption

23. DYL
1. What are the three types of volcanos?
2. What is a hot spot?