1. Volcanoes and Other Mountains
As a scientifically literate citizen, what 3 questions would you ask about this volcano if you moved to the city in the foreground (Tacoma, Washington)?
The Good Earth/Chapter 6: Volcanoes and Other Mountains

2. The Volcano Commandos 1,500 active volcanoes worldwide
a third have records of previous eruptions
2 or 3 eruptions per decade are major disasters
500 million people live near active volcanoes
Fewer than 200 volcanoes have instruments to assess potential for eruption
The Good Earth/Chapter 6: Volcanoes and Other Mountains

3. What exactly is a Volcano?
Location where molten rock and other mantle materials, are released, to the surface.

4. Parts of the Volcano Magma: Lava: Molten rock Less dense than crust
Crater
Magma:
Molten rock
Less dense than crust
Lava:
Magma that has reached the surface and erupted out of the volcano
Lava
Pipes
Central vent

5. Parts of the Volcano Magma Chamber Pipes Vents Crater
Underground pools of magma
Pipes
Pathways for magma
Vents
Area where magma reaches the surface
Crater
Depression at the top of a volcanic form after an eruption

6. 2 Types of volcanoes Shield Made from fast flowing basaltic lava
(Basaltic: A hard, dense, dark volcanic rock)
Large and flat due to movement of the lava

7. Hawaiian Islands formed this way

8. - how-was-hawaii-formed

9. Volcano types 2. Strato-volcanoes
majority of the worlds volcanoes are these
most explosive and destructive
Associated with subduction zones

10. Where do they occur? All boundaries except transform
Famous Volcanoes / areas of volcanoes

11. The Mount St. Helens Eruption
Cascade Mountains – volcanic arc in Pacific Northwest
Major cities within 100 km of active volcanoes
Mount St. Helens eruption of May 18, 1980
The Good Earth/Chapter 6: Volcanoes and Other Mountains

12. The Mount St. Helens Eruption
Cascade Mountains
Volcanoes formed above subduction zone where Juan de Fuca plate slides beneath North America
Mount St. Helens is most active volcano in conterminous US
The Good Earth/Chapter 6: Volcanoes and Other Mountains

13. The Mount St. Helens Eruption
Prior Activity
Early (March) unrest featured
Minor eruptions
Earthquakes
Release of volcanic gases
Followed by change in shape of cone (bulge on North flank)
Increasing frequency of earthquakes
The Good Earth/Chapter 6: Volcanoes and Other Mountains

14. The Mount St. Helens Eruption
May 18 Eruption
A moderate earthquake triggered a massive landslide (debris avalanche) on the North side of the volcano
Debris clogged streams
Pressure released on near-surface magma
Lateral blast produces an initial sideways eruption to North
Later vertical eruption
The Good Earth/Chapter 6: Volcanoes and Other Mountains

15. Eruption of Mount St. Helens reduced height of volcano by 400 meters
Features near volcano were blown over or carried away by products of eruption
Geologist David Johnston (right) died at this site (Johnston’s Ridge) located 10 km from the volcano. (this is 6.25 miles or from here to the pro-football hall of fame.
The Good Earth/Chapter 6: Volcanoes and Other Mountains

16. Products of Volcanic Eruptions
Major products of volcanic eruptions:
Airborne – lateral blast, tephra, volcanic gases
Flows on land – lava, pyroclastic flows, lahars
The Good Earth/Chapter 6: Volcanoes and Other Mountains

17. Products of Volcanic Eruptions
Airborne Eruption Products
Rare lateral blasts can destroy objects up to 12 km away and knock down trees more than 25 km distant
Effect of lateral blast only seen on North flank of Mount St. Helens
The Good Earth/Chapter 6: Volcanoes and Other Mountains

18. Products of Volcanic Eruptions
Airborne Eruption Products
Tephra represents particles blasted into air by eruption
Volcanic bombs and ash are found near and far from eruption source, respectively
Blobs of magma solidify to form lava bombs
Wind can transport fine volcanic ash for hundreds of kilometers downwind
The Good Earth/Chapter 6: Volcanoes and Other Mountains

19. Products of Volcanic Eruptions
Airborne Eruption Products
Volcanic gases (water vapor, sulfur dioxide, carbon dioxide) may affect climate patterns
Sulfur dioxide may block insolation, temporarily (up to 1 year) reducing global temperatures
Widespread release of carbon dioxide and higher temperatures due to faster rates of volcanic activity approximately million years ago
Trees killed by excessive carbon dioxide released by magma under Mammoth Mountain, California.
The Good Earth/Chapter 6: Volcanoes and Other Mountains

20. Products of Volcanic Eruptions
Eruption Products on Land
Low viscosity lava can flow up to 50 km from its source
Lava transported to front of lava flows in long lava tubes
Lava flows build up in a series of layers
The Good Earth/Chapter 6: Volcanoes and Other Mountains

21. Products of Volcanic Eruptions
Eruption Products on Land
Low viscosity lava can flow up to 50 km from its source
Lava transported to front of lava flows in long lava tubes
Lava flows build up in a series of layers
Walter’s Kalapana store, Hawaii, was buried in lava within a few weeks in 1990
The Good Earth/Chapter 6: Volcanoes and Other Mountains

22. Products of Volcanic Eruptions
Eruption Products on Land
Higher viscosity lava remains within volcano crater
Lava dome formed in crater of Mount St. Helens
The Good Earth/Chapter 6: Volcanoes and Other Mountains

23. Products of Volcanic Eruptions
Eruption Products on Land
Pyroclastic flow – dense cloud formed from combination of tephra and volcanic gases
Fast moving, up to 700 C
The Good Earth/Chapter 6: Volcanoes and Other Mountains

24. Products of Volcanic Eruptions
Eruption Products on Land
Lahars – mudflows formed when volcanic debris mixes with streams or melting ice
Often confined to stream channels
Lahar along Muddy River reached depths of 20 meters following Mount St. Helens eruption
The Good Earth/Chapter 6: Volcanoes and Other Mountains

25. Ring of fire area surrounding the pacific plate with VERY high activity of Volcanoes