Geology 309 - Lecture 2

Plate tectonics and volcanoes

I. Start with Earth structure:

Compositional layers

• core - Fe,Ni.
• mantle - compositionally homogenous, made up of peridotite rock
• crust - compositionally heterogeneous, lots of rock types

Mechanical layers

• inner and outer core
• mesosphere (lower mantle)
• asthenosphere - warm, ductile, weak, mantle beneath lithosphere
• lithosphere - cold, brittle, strong, uppermost crust and mantle

II. Plate Tectonic Review

1. Cutaway of Earth - mechanical and compositional layers
2. Topography of the Seafloor and Continents
3. Location of earthquake epicenters around the globe
4. Location of spreading ridges and trenches
5. Associations of volcanoes and plate boundaries
6. Spreading centers, from continental rifting to open ocean basin
7. Subduction zone cutaway
8. "Random"(?) volcanoes not associated with plate boundaries (i.e., they are related to a hotspot in the middle of a plate)
9. Cross section of Hawaiian hotspot track

Volcanoes Associated with Spreading/Rifting
10. Basin and Range - continental rifting

Wide range of volcanic styles from basaltic cinder cones to huge (30 miles X 15 miles) rhyolitic collapse calderas
11. East African rift
12. Topography of the mid-Atlantic ridge
13. Underwater pillow lavas: Mid ocean ridges
14. Pillow lavas exposed on land
15. Fire fountains - icelandic eruption
16. Lava flows - icelandic eruption
17. hardened basalt layers - icelandic eruption
18. Columbia River basalts (17-15 million years ago) with hotspot track back to Snake River Plain and Yellowstone


Volcanoes Associated with Hotspots - commonly basaltic in ocean basins, but can be basaltic to rhyolitic if on continents
19. Mauna Loa - classic shield volcano - Hawaiian eruption
20. Summit crater at Mauna Loa
21. Lava flow (pahoehoe, typical Hawaiian style)


Volcanoes Associated with Subduction Zones - Wide variety of eruption styles, usually somewhat explosive
22. Subduction zone cutaway
23. Ring of Fire
24. Agua Volcano, Guatemala (classic stratovolcano)
25. Paricutin eruption (Mexico) - Strombolian eruption
26. Villarica eruption (Chile) - Strombolian eruption
27. Vulcano, Vulanello, and Lipari islands in Italy - eponym of volcanoes
28. Mt. Pelee, Martinique - site of Pelean eruption in 1902 (see section 4.3 in your text for details of this eruption)
29. Pelean style eruption (actually is a pyroclastic flow, but general style is Pelean)
30. Mt. St. Helens before eruption
31. Mt. St. Helens eruption - Plinian
32. Pinatubo eruption - Plinian
33. Yakima in mid-day on day of Mt St. Helens eruption - dark!
i34. Crater Lake (caldera from catastrophic Plinian eruption of Mt. Mazama)





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