1. Volcanoes
Bob Leighty
GLG Physical Geology

2. These notes and web links are your primary “lecture” content in this class. Additionally, various articles are assigned each week to supplement this “lecture” information. I believe you’ll have enough information to reference without having to purchase a costly textbook.
These lecture notes are very similar to the ones I use in my traditional classes. You’ll find they are loaded with imagery and streamlined text that highlight the most essential terms and concepts. The notes provide a framework for learning and, by themselves, are not meant to be a comprehensive source of information.
To take advantage of the global knowledge base known as the Internet, I have included numerous hyperlinks to external web sites (like the Wikipedia, USGS, NASA, etc.). Follow the links and scan them for relevant info. The information from linked web sites is meant to supplement and reinforce the lecture notes – you won’t be responsible for knowing everything contained in them.
As a distance learning student, you need to explore and understand the content more independently than in a traditional class. As always, I will help guide you through this learning adventure. Remember, Dr. Bob if you have any questions about today’s lecture
Leave no questions behind!
Explore and have fun!

3. What Controls Eruptions?
Volcanoes
What Controls Eruptions?
Amount of gas (water) in the magma
> As magma rises, P decreases & water turns to steam that can propel the eruption
> More gas (water) = more explosive
> Less gas (water) = less explosive

4. What Controls Eruptions?
Volcanoes
Magma composition
> Viscosity strongly influenced by wt% SiO2, temperature, etc.
Mafic lavas are more fluid (lower wt% SiO2, higher T = low viscosity = flow easily)
(less explosive eruptions)
Felsic lavas are more viscous (higher wt% SiO2, lower T = high viscosity = more “sticky”)
(more explosive eruptions)

5. Volcanism Review Table
Volcanoes
Volcanism Review Table

6. Volcanoes of the World Volcanoes
Current volcanic eruptions

7. Volcanoes
Volcano Types
WWW
Flood Basalts

8. Volcanoes
Volcano Types
Flood Basalts

9. Volcano Types Flood Basalts Volcanoes Columbia River (USA)
Deccan Traps (India)

10. Volcanoes
Volcano Types
WWW
Shield Volcanoes

11. Fernandina (Galapagos Islands, Ecuador)
Volcanoes
Volcano Types
Shield Volcanoes
Mauna Loa (USA)
Fernandina (Galapagos Islands, Ecuador)

12. Volcano Types Shield Volcanoes ~11 Mya 1.3 Mya Volcanoes
Joes Hill (AZ)
~11 Mya
Arlington Mesa (AZ)
1.3 Mya

13. Volcanoes
Volcano Types
WWW
Cinder/Scoria Cones

14. Cerro Negro (Nicaragua)
Volcanoes
Volcano Types
Cinder/Scoria Cones
Cerro Negro (Nicaragua)
Paricutin (Mexico)

15. Volcano Types Cinder/Scoria Cones 71,000 years ago 800 years ago
Volcanoes
Cinder/Scoria Cones
SP Crater (AZ)
Sunset Crater (AZ)
71,000 years ago
800 years ago

16. Volcanoes
Volcano Types
WWW
Stratovolcanoes

17. Volcano Types Stratovolcanoes Volcanoes Mt. Saint Helens (WA, USA)
Mt. Fuji (Japan)
Popocatapetl (Mexico)
Mount Mayon (Philippines)

18. San Francisco Peaks (AZ, USA)
Volcanoes
Volcano Types
Stratovolcanoes
San Francisco Peaks (AZ, USA)
500 Kya

19. Volcanoes
Volcano Types
WWW
Lava Domes

20. Mount Saint Helens (WA, USA)
Volcanoes
Volcano Types
Lava Domes
Mount Saint Helens (WA, USA)
Mount Unzen (Japan)

21. Volcano Types Lava Domes Volcanoes Sugarloaf Mountain (AZ, USA)
Elden Mountain (AZ, USA)

22. Volcanoes
Volcano Types
WWW
Calderas

23. Volcano Types Calderas Volcanoes Yellowstone (WY, USA)
Long Valley (CA, USA)
Valles (NM, USA)
Krakatau (Indonesia)

24. Volcano Types Calderas Volcanoes Superstition Mountains (AZ, USA)
Chiricahua Mountains (AZ, USA)

25. WWW Links in this Lecture
Volcanoes
> Viscosity -
> Mafic -
> Felsic -
> Volcanism review table -
> Current volcanic eruptions -
> Flood Basalt -
> Shield volcano -
> Cinder cone -
> Stratovolcano -
> Lava dome -
> Caldera -