1. Volcanoes
Unit 2

2. Diagram to label: Blue = vent Green = crater Yellow = cone
Orange = pipe
Red = Magma chamber

3. What is a Volcano?
Volcano—cone-shaped mountain or hill from which lava, rock, and hot vapors erupt
Crater—the depression at the top
Vent—the opening inside the crater
Pipe—pathway magma travels from the mantle to the vent
Cone—the mountain/hill
Magma Chamber—where magma sits in the crust prior to an eruption

4. Magma vs. Lava Magma—molten (melted) rock inside the crust and mantle
Lava—molten (melted) rock on top of the Earth’s crust
Lava
Magma

5. 3 Types of Volcanoes
Types are determined by 2 things:
Cone Composition—cone made of cinders, lava, or both
Explosive Power—strength of eruption
Determined by:
Amount of dissolved gases in magma
Magma temperature
Magma composition (type of rock)

6. 3 Types of Volcanoes: Shield Volcanoes
Cone:
Composed mostly of cooled, hardened lava
Gently sloped with a broad base
Nonexplosive
Example: Mauna Loa and Hawaiian Islands

7. 3 Type of Volcanoes: Cinder-Cone Volcanoes
Composed mostly of cinders
Steep sides with a small base
Very explosive
Most common type
Example: Nyamuragira Volcano, Rep. of Congo

8. 3 Types of Volcanoes: Composite Volcano (Stratovolcano)
Cone
Alternating layers of cinders and lava
Steep sides with a large base
EXTREMELY violent explosions
Example: Arenal, Costa Rica

9. Indicators of Imminent Eruption
Increase gas emission
Localized tremors/small earthquakes

10. Types of Pyroclastic Material
Pyroclastic Material = ejected from volcano
Volcanic bombs—large lava blobs
Lava blocks—large pieces of rock; angular shapes; solid
Lapilli—pea-size to walnut-sized pieces of volcanic rock
Cinders—very small; cool very quickly; contain many air bubbles

11. Popular Volcano Locations
80% of volcanos occur at convergent boundaries (due to subduction)
Oceanic-oceanic = volcanic island arcs
Oceanic-continental = continental volcanoes
15% occur at divergent boundaries
5% occur at HOT SPOTS—magma punches through thin lithosphere where there is no boundary; example: Hawaii

12. Popular Volcano Locations

13. Popular Volcano Locations: Ring of Fire
Pacific Plate is subducting on all sides
West—by the Eurasian and Indo-Australian plates
East—by the North American and Nazca plates
Both subduction zones create sites favorable to both volcanoes and earthquakes

14. Volcanic Impacts Lahar (mud) flows Volcanic debris saturated
with water from rain, melting ice, or snow
Atmospheric Ash
Ash leads to rain, lightning and thunder
Volcanic fog—water vapor, carbon dioxide, nitrogen, & sulfur
Sulfur condenses to form acid rain