1. Earth’s Structure
core: solid center surrounded by molten layer, mostly iron and nickel;
mantle: solid zone with hot, partly molten "plastic" upper layer known as asthenosphere; rich in iron, silicon, oxygen, & magnesium;
crust: outermost thin layer, location of mineral resources & soil.
lithosphere: solid crust and uppermost part of mantle. This layers is divided into several Tectonic Plates

2. Plate Tectonics “Ring of Fire”:
Earthquakes & volcanoes are distributed mostly in bands along the Earth's surface. These bands correspond to tectonic plate boundaries.

3. Plate Tectonics Plate boundaries
undersea mountain chains (diverging plate boundaries)
deep sea trenches (converging boundaries)

4. Major Plates on Earth

5. What Drives Plate Tectonics?
Heat escaping from core creates convection currents in the asthenosphere
Where currents rise, plates are pulled apart (divergence)

6. Plate Tectonics Types of boundaries Divergent Boundaries:
Convergent Boundaries:
Transform Boundaries:

7. Divergent Plate Boundaries
Plates moving apart due to rising magma below.
New oceanic crust is formed
Eruptions are all basaltic (non-explosive)
Undersea mountain chain is created called a mid- ocean ridge
Process widens existing oceans (i.e. Atlantic ocean), or creates new ones (Red Sea, Great Rift Valley in Africa)

8. Evidence of Sea Floor Spreading
Youngest rock found at mid ocean rift.
Periodic reversals of the polarity of the Earth’s magnetic fields. Mirror images of
magnetic polarity on either side of rift.

11. Divergent Plate Boundaries
Divergence splits up continents.

12. Divergent Plate Boundaries
The Red Sea is a newly forming ocean
The rift valleys in Africa are splitting it apart

13. Hydrothermal Vents at Divergent Boundaries

14. Convergent Plate Boundaries
Plates moving towards each other.
Denser, thinner plate is subducted beneath the other plate
Subducted plate is melted and produces explosive volcanoes on upper plate
Three Types:
Ocean-Ocean collision
Ocean-Continent collision
Continent-Continent collision

15. Convergent Plate Boundaries

16. Ocean-Ocean Collisions
Older, denser ocean plate gets subducted and melts
Deep trench is formed by bending of down-going plate
Chain of volcanic islands is formed on upper plate = Island Arc. Example: Japan
All islands are approximately the same age
Volcanoes are explosive due to sediments (silica-rich) which get subducted with ocean plate
Volcanoes are tall and pointy

17. Ocean-Ocean Collisions Cont.
Examples include all the volcanic islands in the Western Pacific
Island chains are usually arc-shaped
Mineral-rich hydrothermal deposits may occur

18. “Accretionary Wedge” forms when lots of sediment on subducting plate cannot be forced down, so it piles up in front of the upper plate
Accretionary wedges are non-volcanic (mostly scrunched up sediment)
Example: Barbados

19. Ocean-Continent Collisions
Ocean crust gets subducted because it is denser and melts beneath continent
Explosive volcanoes form on continental plate (silica-rich due to subducted sediment and melted continental crust)
Volcanoes are approximately the same age and are tall and pointy
Trench is formed off the coast
Mt. Shasta

20. Ocean-Continent Collisions Cont.
Cascades in Pacific Northwest
Andes in S. America
Hydrothermal mineral deposits often occur (gold in CA)

21. Ocean-Continent Collisions
What about the Olympics and the mountains on Vancouver Island?
Olympics are non- volcanic, and marine fossils are found in its tallest peaks
Sedimentary layers are extremely folded
Accretionary Wedge (like Barbados)

22. Continent-Continent Collisions
Continental crust is too thick and not dense enough to subduct, so very tall mountains are produced
Mountains are non-volcanic
Himalayas are still rising
Older examples: Alps Appalachians

23. Transform Plate Boundaries
Fig.14–4c
Plates slide in opposite directions past each other
Transform faults occur usually this occurs between different segments of mid-ocean ridges
No volcanic activity occurs along transform faults
Earthquakes are common

24. Transform Plate Boundaries Cont.
The San Andreas fault connects two diverging plate boundaries, and is one of the only continental transform faults.
Bay Area
S. Cal

25. Hot Spots Hawaii Not located at plate boundaries.
Deep magma source stays
stationary as plate moves over it.
Hot Spots under Oceanic Plates produce a chain of volcanic islands which get older away from the
hot spot (i.e. Hawaii)

26. Hot Spots Hot spots erupting through ocean crust erupt only basalt
-Eruptions are non-
explosive
-Volcanoes are shield type (wide, non-pointy)
Mauna Loa

27. Hot Spots Cont.
Hot Spots underneath Continental crust produce flood basalts and calderas (i.e. Deccan Traps, Yellowstone)
Hot spot can melt portions of the continental crust (silica-rich), creating a massive, explosive eruption which leaves a caldera (big hole) behind
Hot spots can have very active
hydrothermal circulation, which will
produce metal ore deposits
The stationary deep hot spot does not seem affected by convection in mantle, which moves the plates above it.
Deccan Traps

28. Yellowstone Hot Spot and Caldera

29. Geothermal Resources

30. Surface Geologic Processes
erosion: the process by which earth materials are transported from one location & deposited in other locations (forming sedimentary rocks)
weathering: physical & chemical processes in which solid rock exposed at the earth's surface is changed to separate solid particles & dissolved material;
weathering is responsible for the development of soils;
streams are the most important agent of erosion.