1. Geography grade 8 to 10

2. Earthquakes

4. What produces an earthquake ?
Plate movements
Cause cracks or faults
In the earth’s crust.
These faults produce
Stresses which cause
Vibrations.
These vibrations are
Called earthquakes.

5. TERMS

6. Seismic Waves

7. P, S and Waves
The P and S waves pass through the crust from the focus to the surface.
On the surface they become L waves where they cause the most damage.
They cause movement in the following three ways:
-up and down
-backward and forward
-from side to side

8. TSUNAMIS They are huge sea waves Which are experienced in
Shallow waters along coastlines.
It reaches heights of between 10 and 30 metres.

9. Measurement of Earthquakes
-Seismograph and the Richter
Scale

10. The Richter Scale It measures the size of the seismic waves and their
Speed to classify the magnitude of the earthquake in
Terms of energy released.
The scale extends from 1-9 .
Each step represents a magnitude 10 times greater than the previous step.

11. Earthquake regions