1. Volcano Notes

2. Anatomy of a volcano magma chamber pipe vent/crater lava tephra

3. 3 Types Volcanic Materials 1.Magma- hot - melted rock (molten) - beneath the Earth’s surface

5. 2. Lava- hot - molten rock - flowing on Earth’s surface

6. 3. Tephra -lava that is blasted into the air - turns solid as it falls back to the ground

7. Examples of tephra: ash, cinders, and volcanic bombs (*pyroclastic material* )

8. Some volacanic eruptions are violent and explosive…

9. Some are quiet eruptions

10. 3 Factors that Affect the Explosiveness of Volcanoes 1. Amount of trapped gases and water vapor

12. Just like a closed soda can, the pressure builds when shaken. In a volcano, the more gas that is trapped, increases pressure, and makes the eruption more explosive

13. 3 Factors that Affect the Explosiveness of Volcanoes 2.Composition and viscosity of magma The elements and minerals that make up the melted rock determine how explosive an eruption will be. High amounts of silica increase the viscosity of the magma.

15. Basaltic magma is relatively liquid (low viscosity ; low silica content) when melted and is not usually explosive

16. Rhyolitic magma is very thick (high viscosity ; high silica content) when molten, and therefore very explosive

17. 3 Factors that Affect the Explosiveness of Volcanoes 3. Temperature of the magma (affects viscosity and explosiveness)

18. 3 Volcano Types Volcano shape and size is related to: – Type of material in an eruption – Gas content – How often the volcano erupts

19. 1. Shield Volcano Gradual slope (gives “shield” shape) Layers of lava built up over time Low to moderately explosive Ex. Hawaiian Island volcanoes

20. 2. Cinder Cone Volcano Very steep slopes Made of tephra (accumulated cinders and rock particles) Moderate to highly explosive Ex. Wizard Island – Crater Lake, Oregon

21. 3. Composite Volcano (Stratovolcano) Steep slopes Made of layers of tephra and lava Moderate to highly explosive Ex. Mt. St. Helens – Cascade volcanoes

23. Image credits Slide 2 volcano: http://cgz.e2bn.net/e2bn/leas/c99/schools/cgz/accounts/staff/rchambers/GeoBlo gBytes%20Blog%20Resources/Year%209/Volcano_structure.png Slide 4 mt st helens: http://www.driever.nl/foto/achtergronden/JLM-NatGeo- Mount-St-Helens-1980-May-18.jpghttp://www.driever.nl/foto/achtergronden/JLM-NatGeo- Mount-St-Helens-1980-May-18.jpg Slide 4 mauna loa: http://en.wikipedia.org/wiki/File:Aa_channel_flow_from_Mauna_Loa.jpg http://en.wikipedia.org/wiki/File:Aa_channel_flow_from_Mauna_Loa.jpg Slides 9 & 10 shield and cindercone: Tasa Graphics CD Slide 11 stratovolcano: http://www.biocrawler.com/w/images/4/4f/Stratovolcano.jpg http://www.biocrawler.com/w/images/4/4f/Stratovolcano.jpg