1. Ch. 18 Notes Day 1
10/13/16

2. Objectives
SWBAT explain the relationship between the strength and type of a volcanic explosion and the type of rock and debris it produces
SWBAT explain the importance of Silica content in volcanic products an how it controls the strength of the explosion.

3. Ring of Fire
The Ring of Fire is a continuous, 25,000 mile long series of 452 oceanic trenches, volcanic arcs, and volcanic belts associated with numerous plate boundaries in the Pacific Ocean Region

5. Volcanic eruptions produce three major rock types based on the type of eruption.
Basalt
Andesite
Rhyolite

6. Basalt
Low silica content (50%)
Rock Type: Mafic
Low viscosity
Low gas content
Temperature: 1100 C
Associated with non-explosive eruptions.
Produces large basalt floes
Material Source: Oceanic crust at divergent boundaries

7. Shield Volcano
Quiet, non-explosive eruption (lava comes out slowly) of usually basaltic lava.
Made of layers of solidified basaltic lava
Gentle slopes

8. Andesite Medium silica content (60%)
RockType: Mafic/Felsic (Intermediate)
Medium Viscosity
Medium Gas Content
Temperature: 1000 C
Associated with semi- explosive to explosive eruptions.
Material Source: Oceanic & Continental crust at convergent oceanic-continental boundaries.

9. Composite or stratovolcanoes
Repeated cycle of non-explosive and explosive eruptions
Built from alternating layers of tephra and lava
Typically produce andesite and rhyolite
Tall and majestic

10. Rhyolite High silica content (70%) Rock Type: Felsic High viscosity
High gas content
Temperature: 800 C
Associated with highly explosive eruptions.
Material source: Continental crust from continental-continental convergent boundaries

11. Cinder Cone Volcano Explosive Eruptions
Steep Slopes built from tephra (ash and rocks)
Smallest of all volcanoes
Usually form at edges of larger volcanoes
Usually made from basalt and rhyolite

12. Ch. 18 Notes Day 2

13. Objectives
SWBAT explain the anatomy of a volcano
SWBAT the difference materials that are ejected from a volcano during an eruption and their effect on the surrounding environment

14. Caldera Volcano Most Explosive Eruptions
Volcano literally blows itself up and creates a large crater
Typically produce rhyolite

15. Anatomy of a Volcano

16. Tephra – mixture of ash, rocks, lava, and pyroclasts (lava that hardens in mid air) thrown from a volcano as it erupts.
ASH –
Very fine-grained fragments
(< 2 mm)
BLOCKS –
Very large pyroclasts launched from a volcano
LAPILLI –
Pea- to walnut-size pyroclasts (2 to 64 mm). They often look like cinders
BOMBS –
Fragments
(> 64 mm)

17. Gasses Given off During Eruptions
The most abundant gas is water vapor (H2O), followed by
carbon dioxide (CO2) (green house gas, contributes to global warming)
sulfur dioxide (SO2) (very poisonous)
Secondary gases are also include:
hydrogen sulfide (H2S),
hydrogen (H)
carbon monoxide (CO)
hydrogen chloride (HCl)
hydrogen fluoride (HF)
helium (He)

18. Magma vs. Lava Magma is molten rock trapped BELOW the earth’s surface
Lava is molten rock AT or ABOVE the earth’s surface

19. Pyroclastic Flows
Mixture of ash, gases, and tephra that “avalanche” from a volcano
Hot (> 700 °C)
Can be faster than 100 mph

20. Hot Spot
Unusually hot regions of Earth’s mantle where high- temperature plumes of magma rise to the surface.
Can be linked to the path of convergent plate boundaries