1. Volcanoes
Chapter 18
Page 498

2. 18.1 Zones of Volcanism
Volcanism = describes all the processes associated with the discharge of magma, hot fluids and gases.

3. Ring of Fire
Active volcanoes that create a “ring” pattern in the pacific ocean
Typically volcanoes from convergent and divergent boundaries.

4. Convergent Volcanoes
Volcanoes that form from plates colliding or subducting.
Land volcanoes tend to be explosive

5. Divergent Volcanism 2/3rds of volcanism underwater
The ocean ridges that form tend to release giant pillow lava.
Tend to be non-
Explosive and large

6. Hot Spots Volcano that forms NOT at a plate boundary.
Magma rises from HOT areas of the mantle

7. Anatomy of a Volcano Conduit = tube Vent = opening Crater = depression
around the vent

8. Calderas Large crater that may have formed from a large explosion.
Sometimes forms into a lake

9. Types of Volcanoes 1. Shield Volcanoes 2. Cinder Cones
3. Composite Volcanoes
All three depend on 2 factors:
Type of material that forms it
Type of eruption

10. Shield Volcano Broad, gently sloping, circular base
Largest in size of the 3 types
Nonexplosive eruption which leaves layers of lava.

11. Cinder Cone
Formed from explosive eruptions that eject small pieces of magma from the air.
The small pieces pile back around the vent causing the cinder cone shape.
Small and steep

12. Composite Volcanoes Violent eruptions
Formed by layers of hardened chunks of lava from the eruptions alternating between explosions and oozing of lava
Cone shaped with
concave slopes
(larger than cinder)

13. 18.2 Explosive Eruptions
Tephra = is the erupted material from the volcano.
Can be solidified lava OR pieces of crust
Classified by size:
Less than 2 mm is called ASH
Largest is called BLOCKS

14. Explosion effects Ash can rise into atmosphere hurting: Airplanes
Change in weather - Block sun’s rays therefore lower temps

15. Proclastic Flows Clouds of ash and other tephra
Travels at speeds of 125 mph
Mixed with hot gases
up to temps of 700*C
Can kill thousands AFTER
the explosion