1. Earthquakes and More

2. What is Plate Tectonics
The Earth’s crust and upper mantle are broken into sections called plates
Plates move around on top of the mantle like rafts

4. Plate Boundaries 1. Divergent 2. Convergent 3. Transformational

6. Divergent Boundaries
Boundary between two plates that are moving apart or rifting
 
causes SEAFLOOR SPREADING

10. Convergent Boundaries
Boundaries between two plates that are colliding
 

12. Andes Mountains, South America

13. Aleutian Islands, Alaska

16. Transformational Plates
Boundary between two plates that are sliding past each other
They move in Jerks!
EARTHQUAKES along faults

17. Fault? Is a narrow zone in the earth about 10 miles deep.

18. San Andreas Fault, CA
Separates the Pacific Plate and North American Plate
The Pacific plate moves about 4 inches per year.

20. What are Earthquakes?
The shaking or trembling caused by the sudden release of energy
Usually associated with faulting or breaking of rocks

21. The Focus and Epicenter of an Earthquake
The point within Earth where faulting begins is the focus.
The point directly above the focus on the surface is the epicenter

22. What is the Elastic Rebound Theory?
Explains how energy is stored in rocks
Rocks bend until the strength of the rock is exceeded
Rupture occurs and the rocks quickly
Energy is released in waves that radiate outward from the fault

23. Elastic Rebound

24. Seismographs record earthquake events & measure seismic waves

25. Seismograms
Electronically recorded ground motion made by seismographs

26. Where Do Earthquakes Occur and How Often?
~80% of all earthquakes occur in the circum-Pacific belt
more than 150,000 quakes strong enough to be felt are recorded each year

27. The Economics and Societal Impacts of EQs
Damage in Oakland, CA, 1989
Building collapse
Fire
Tsunami
Ground failure

28. Seismic Earthquake Waves?
Body waves – in ground
P and S waves
(Primary and Secondary)

29. Body Waves (Ground Waves): P and S waves
Body waves (in the ground)
P or primary waves
fastest waves
travel through solids, liquids, or gases
compressional wave, movement is in the same direction as wave movement
S or secondary waves
slower than P waves
travel through solids only
Move perpendicular to wave movement

30. Earthquakes generate Surface Waves
. Surface waves (above the ground – on surface)
R and L waves
(Rayleigh and Love)

31. Surface Waves: R and L waves
Travel just along the grounds surface
Slower than body waves; rolling up and down or side- to-side movement
Especially damaging to buildings

33. To locate an earthquake you need to measure the time between the P and S waves.
P waves arrive first, then S waves, then L and R
3 Seismograms are needed to locate the earthquake.

34. How are the Size and Strength of an Earthquake Measured?
Magnitude
Richter scale measures total amount of energy released
A magnitude 6.0 earthquake is 10 times greater than a 5.0, a 7.0 is 100 times greater, and a magnitude 8.0 is 1,000 times greater.

36. Layers Defined by Composition
Earth’s interior consists of three major zones defined by their chemical composition—
Crust
Mantle
Core (inner & outer) • •

37.  Crust – thin rocky layer•
The Crust is about 25 miles beneath the continents and about 6.5 miles thick beneath the oceans. It is light and brittle. Most earthquakes occur within the crust.

38. The Mantle
 Mantle
The region just below the crust extending all the way to the earth’s core is called the mantle. It is relatively flexible so it flows instead of fracturing. (Lava)

39. The Core (Inner & Outer)
• Below mantle is the earth’s core. The core consists of a fluid outer core and a solid inner core.
The outer core contains iron, when it flows it generates a magnetic field. This is the source of the Earth’s magnetic field. The inner core is solid

40. Earth’s Layered Structure