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Lets Review… Copy in Notebook and Answer: –Compare and contrast magma and lava. –What plate boundaries will result in formation of a volcano?

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Presentation on theme: "Lets Review… Copy in Notebook and Answer: –Compare and contrast magma and lava. –What plate boundaries will result in formation of a volcano?"— Presentation transcript:

1 Lets Review… Copy in Notebook and Answer: –Compare and contrast magma and lava. –What plate boundaries will result in formation of a volcano?

2 Magma What caused Mt. St. Helens to erupt?

3 How does Magma form? Magma is molten rock beneath the Earths surface High Temperature: –Rocks melt at 800-1200°C

4 Viscosity Viscosity – internal resistance to flow Low Viscosity – Moves fast (Less thick) High Viscosity – Moves slow (More thick)

5 Types of Magma

6 Type of Magma Viscosity Silica Content Gas Content Explosive- ness Type of Volcano Example

7 Type of Magma Viscosity Silica Content Gas Content Explosive- ness Type of Volcano Example BasalticLow 1-2% 50% LeastShield Hawaii

8 Type of Magma Viscosity Silica Content Gas Content Explosive- ness Type of Volcano Example BasalticLow 1-2% 50% LeastShield Hawaii Andesitic Medium 3-4%60% Medium Composite Mt. St. Helens

9 Type of Magma Viscosity Silica Content Gas Content Explosive- ness Type of Volcano Example BasalticLow 1-2% 50% LeastShield Hawaii Andesitic Medium 3-4%60% Medium Composite Mt. St. Helens Rhyolitic High 4-6%70% Greatest Cinder Cone Yellowstone *The higher the gas content, the more explosive the magma is going to be

10 Volcanic Material Tephra – Rock fragments thrown into the air during a volcanic eruption Pyroclastic Flow –Rapidly moving volcanic material. –Speeds up to 200km/h –May contain hot, poisonous gases

11 Tephra Pyroclastic Flow

12 Shield Volcano Broad Gentle Sloping Sides Non-Explosive

13 Composite Volcano Alternates Lava and Tephra Potentially most dangerous

14 Cinder Cone Volcano Steep sides caused by tephra landing around vent Explosive


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