1. Physical Science 3-31-08 4th MP

2. Welcome to the last Marking Period of the year!

3. Topics Earthquakes Introduction to Chemistry

4. Grades are not finalized Need to finish Grading Last Tests

5. Big Questions about Earthquakes

6. What is an earthquake?

7. An earthquake is The vibration of the earth caused by the sudden motion of tectonic plates Energy is transferred in a series of seismic waves through the earth from the origin of the motion

8. Why does an earthquake occur?

9. Why do earthquakes occur? Because motion of tectonic plates is not constant Force has to build up to overcome friction between plates

10. Where do earthquakes occur?

11. Where do earthquakes occur Earthquakes are normally near plate boundaries Any motion of plates can generate earthquakes Divergent boundaries Convergent boundaries Transform boundaries The surface line of intersection of intersection of 2 plates is called a fault line

12. Faults around Southern California

13. Why are all earthquakes not the same?

14. What makes a difference between earthquakes? Related to the amount of force and energy associated with the movement of the plates at a boundary (transform, convergent more) Depends on the location where earthquakes originates in the earth (the focus). Deep focus earthquakes are less dangerous The point on the surface above focus is called the epicenter

16. What are aftershocks and are they dangerous?

17. What are aftershocks? When one section of a plate boundary experiences an earthquake, the entire plate does not move. Those portion that do not originally move are placed under greater force (stress), which can result is subsequent earthquakes at other points along the boundary (fault line)

18. Are aftershocks dangerous? They can be as strong as the original Buildings already weakened from the first may collapse after additional earthquakes

19. How can an earthquake cause damage/harm?

20. Motion of buildings/bridges/roads causes collapse Rupture of gas/oil lines cause fires Falling glass, pieces of buildings Disruption of food/medical supply lines Loss of shelter Tsunami’s along the coast for major earthquakes

21. How are earthquakes measured?

22. A scale based on the energy released by an earthquake was developed. Named after its creator, Richter Another scale based on damage done was developed Named after its creator, Mercalli

23. Richter is most reported Logrithmic in nature, therefore doubling the value more than doubles the energy Under 4, not felt by humans 4-5.5 are significant earthquakes,that cause minor damage in 1 st world countries, major damage in 3 rd world countries

24. Richter scale 5.5 – 8 major earthquake, can cause significant damage 8 – 9.5 once in a generation quake, major damage >9.5 wow, run for the hills (if they are still there)

25. How long do quakes last?

26. Small quakes last for less than 30 seconds Significant quakes between 30 seconds and 2 minutes Major quakes upwards of 4 minutes