1. Chapter 9: Earthquakes 9.1: Earthquakes occur along faults
9.2: Earthquakes release energy
9.3: Earthquake damage can be reduced

2. 9.1: Earthquakes occur along faults
Review, true or false?
Earth’s lithosphere consists of the uppermost mantle and core?
Earth’s lithosphere consists of the crust and uppermost mantle
Earth’s lithosphere is hot and liquid?
Earth’s lithosphere is cold and rigid
Tectonic plates move over the asthenosphere?
True

3. 9.1: Earthquakes occur along faults
Rocks move along faults
Fault: fracture, or break, in Earth’s lithosphere, along which blocks of rock move past each other
Rocks may slide smoothly or stick or lock together
Rocks may bend as stress is applied
Stress: force exerted when an object presses on, pulls on, or pushes against another object
Sudden release of stress in the lithosphere causes…and earthquake!
Earthquake: shaking of the ground caused by the sudden movement of large blocks of rock along a fault
Video-abc
video – haiti science
Video-haiti science 2

4. Rocks move along faults
Most faults are located along tectonic plate boundaries
What does this mean for earthquake locations?
The blocks of rock moving during an earthquake are much smaller than the plate
Block of rock may move only a meter
Earthquake strength depends on:
How much stress builds up before the rocks move
Distance the rocks move along the fault

5. Rocks move along faults
80% of all earthquakes occur in a belt around the edges of the Pacific Ocean!
US: San Andreas Fault: boundary between North American and Pacific Plates

6. Rocks move along faults
Stress along a plate’s boundary can cause rocks to break and move along weak areas toward the middle of the plate
All earthquakes occur…in the lithosphere
Why may a few occur below the normal depth of the lithosphere?
Subduction: plates are still cool enough to break

7. Faults are classified by how rocks move
Rock movement along faults depend on the kinds of stress they are under
Three main faults:
Normal
Reverse
Strikeslip
Type of fault depends on whether plates are pulling apart, pushing together, or scraping past one another
Movement along normal and reverse faults is mainly vertical – the blocks move up and down
Movement along strikeslip faults is horizontal – the blocks move sideways
Investigate p47 two triangular blocks of wood, masking tape, marker

8. Normal Faults Stress that pulls rocks apart cause normal faults
Common where tectonic plates are moving apart
Ex: Great Rift Valley of Africa

10. Reverse Fault Stress that presses rocks together causes reverse faults
Can occur near collision-zone boundaries between plates
Ex: Himalaya Mts, where Indian Plate is pushing into the Eurasian Plate

12. Strike-Slip Faults
Stresses that push blocks of rock horizontally cause earthquakes along strike-slip faults
Can occur where plates scrape past each other
Ex: San Andreas Fault

14. faults