Plate Tectonics and Volcanoes

1
Plate Tectonics and Volcanoes

• Earth Science
• Chapter 14

2

• What are volcanoes?
• Opening in Earths crust through which molten
  rock, gases, and ash erupt and the landform that
  develops around this opening.

3

• What is Magma
• Molten rock that is below the surface of the
  earth
• Located in the mantle
• Forms when rocks melt due to subduction
• What is Lava
• Molten rock that has reached the surface of the
  earth
• Forms when volcanoes erupt

4

• What is magma/lava made of?
• Silica
• Water
• Magnesium
• Iron

5

• What are the different types of magma/lava?
• Granitic (Felsic)
• Made of 70 or more silica
• High viscosity
• Basaltic (Mafic)
• Made of 50 or less silica
• Low viscosity

6

• What does granitic(Felsic) magma look like?
• Light in color
• Contains a lot of water
• Does not flow easily
• Highly viscous
• Often solidifies before reaching the earths
  surface

7

• What does basaltic (mafic) magma look like?
• Dark in color
• Flows easily
• Does not contain a lot of water

8

• What are the different kinds of eruptions?
• Pyroclastic
• Highly explosive
• Felsic
• Lots of stuff- Organized by size
• Bombs
• Extremely large chunks erupted from volcano
• Lampilli
• Smaller than bombs
• Ash
• Fine grained/very small chunks

9

• Non-Pyroclastic
• Non-explosive
• Mafic lava
• Mid-Atlantic Ridge is best example
• Hawaii Islands

10

• What are the different types of volcanoes?
• Shield cone
• Broad or wide
• Not very tall
• Mellow eruptions
• Hawaii
• Cinder cone
• Narrow
• Tall
• Pyroclastic eruptions
• Mexico City
• Composite Cone
• Alternating layer of lava and cinders (ash)
• Alternates pyroclastic and non-pyroclastic
  eruptions
• Mount St. Helens

11

• What type of lava goes with what type of
  eruption?
• Pyroclastic felsic
• Non-pyroclastic mafic

12

• What type of boundary is associated with what
  type of eruption?
• Convergence with subduction
• Pyroclastic and mellow
• Felsic lava
• Divergent
• Non-pyroclastic
• Mafic lava

13
Plutonic Activity

• Solidification of magma in the earths crust
• Hardens in any existing rock
• Types
• Batholiths
• Magma exposed at the earths surface
• Largest
• Exposed at the surface due to erosion
• Stock
• Magma exposed at the earths surface
• Smaller than batholiths
• Exposed due to erosion

14

• Dike
• Magma cools inside a fracture (break in the crust
  with no movement)
• Cut across vertically
• Sill
• Magma goes into rock layers horizontally
• Laccolith
• Magma goes into rock layers horizontally
• Hardens and makes a dome like structure

15
Plutonic Activity
16
Ring of Fire
17
Mafic Lava
18
Felsic Lava
19
Stages of Cinder Cone
20
Cinder Cone
21
Sunset Crater
22
Composite Cone
23
Mt Fuji, Japan
24
Shield Cone
25
Galapagos Islands
26
Volcanoes