1. Warm Up 09/26/2016
What are the three types of boundaries and explain the motion that occurs at each?
What is produced at a Transform Boundary?
What happens at a Subduction Zone?
What does Plate Tectonics Explain?
What layer of the Earth contains convection currents?

2. Earthquakes
2.1.1
Describe the anatomy of an earthquake

3. Essential Question How can I locate the epicenter of an earthquake?
Video
nce/rocks-minerals-landforms/earthquakes.htm

4. What is an earthquake?
An earthquake is a shaking of the ground caused by the sudden breaking and movement of large sections (tectonic plates) of the earth's rocky outermost crust.
Most earthquakes occur along the fault lines when the plates slide past each other or collide against each other.
More than 95% occur along PLATE BOUNDARIES

5. The main cause of an earthquakes is the
Elastic rebound Theory
- The elastic rebound theory is an explanation for how energy is spread during earthquakes.  Rocks become strained and shift.
- Most earthquakes are the result of the sudden elastic rebound of previously stored energy.

6. Ring of Fire
80% of the world’s earthquakes occur in a ring that borders the pacific ocean
This ring is called “the Ring of Fire”

7. This photo shows the Mission District of San Francisco burning after the 1906 earthquake. The greatest damage in earthquakes is often not from the ground shaking but from the effects of that shaking.

8. 1906 San Francisco Earthquake
Gas mains break, fires shaken out of furnaces. Water mains break, cannot fight fires. Debris in streets, Fire department cannot reach fires.

9. Anatomy of an Earthquake

10. Focus Release of energy starts here...
An Earthquake starts at a location inside the Earth called a “focus” (foci). Where the slip happens below ground.
Release of energy starts here...

11. The Focus of an earthquake can occur at many depths
CLASSIFICATION
DEPTH OF FOCUS
Shallow Focus
0 – 70 km
Intermediate Focus
70 – 300 km
Deep Focus
> 300 km
Most Earthquakes have focus less than
100 km deep
Earthquakes occur at various depths, depending on the type of tectonic plate interaction involved. Earthquake at a subduction zone could be deeper than one at a transform plate boundary. A shallow focus earthquake causes greater destruction than a deep focus one.
About 3% of quakes
Shallow Focus earthquakes cause more damage 11

12. EPICENTER
The “epicenter” is the point on the EARTH’s SURFACE directly above the focus.
Epicenter is where the shaking is first felt above
ground directly above the focus.
It is not the center where the Earthquake
starts!

13. Fault Line
A fault line is a fracture along which the crust has moved.

14. Fault
FAULT: A surface or narrow zone along which one side has moved relative to the other.
Faults are classified based upon their direction of movement.

15. Three major Faults
Normal
Reverse
Strike-slip

16. Normal Fault The hanging wall moves down relative to the foot wall.
This fault type is caused by tensional stress.

17. Normal Fault

18. Reverse Fault The hanging wall moves up relative to the foot wall.
This fault is caused by
Compressional stress.
Hanging Wall is the part of the Earth's crust above the plane of the fault

19. Reverse Fault

20. Strike-Slip Fault The fault exists between two pieces of crust and the
Movement occurs
horizontally where
the sides slide past
each other.
This fault type is caused by shear stress.

21. Strike Slip Fault

22. Fault Movement = Earthquakes
An earthquake is caused by a sudden slip on a fault. The tectonic plates are always slowly moving, but they get stuck at their edges due to friction. When the stress on the edge overcomes the friction, there is an earthquake that releases energy in waves that travel through the earth's crust and cause the shaking that we feel.

23. Aftershocks
Aftershocks are earthquakes that follow the largest shock of an earthquake sequence. They are smaller than the main shock and within 1-2 rupture lengths distance from the main shock.
Aftershocks can continue over a period of weeks, months, or years.

24. Exit Ticket 2.1.1 Match the following terms with their definitions.
1. ___ divergent boundary
2.___ rift valley
3.___ convergent boundary
4.___ transform boundary
5. ___subduction zone
1. B 2. E 3. A 4. D. 5. C