1. Earthquakes The Richter scale is used to measure earthquake strength.
The Richter scale is logarithmic.
7.0 is 10 times stronger than 6.0
8.0 is 10 times stronger than 7.0
etc…
Therefore 8.0 is 100 times stronger than 6.0.
Question:
An 8.0 earthquake on the Richter scale releases ___________ times as much energy as a 2.0 earthquake.

2. HOW ARE THEY ALL RELATED?
Plate tectonics
Earthquakes & Volcanoes
HOW ARE THEY ALL RELATED?

3. EVIDENCE for Plate tectonics
Several pieces of evidence support the theory of plate tectonics:
Africa and South America were once part of a larger continent (called Pangaea)
 note similarities in continental shape
 presence of Mesosaurus fossils

6. Evidence Continued Earthquakes and volcanoes
 occur along plate boundaries **(where one plate is moving relative to another)

7. ** Side note
Volcanoes also occur above “hot spots” in the middle of lithospheric plates.
 The hot spot remains in the same location while the plate above moves overtop

8. Evidence Continued Magnetism and spreading centres
 as plates spread apart, new rock* is formed and older rock moves away from the spreading plate boundary
* The rock crystallizes and records the magnetic field of the earth at that particular time

10. Volcanoes
Composite volcanoes - this is the stereotypical volcano, erupting and belching smoke and ash everywhere,
found along converging plate boundaries
Layers of ash and thick lava (magma) form a tall cone.
As magma reaches the surface, it cools, hardens and traps gases below.
Pressure builds, eventually there is an eruption.
See pages

11. Shield volcanoes - these are NOT found at plate
Shield volcanoes - these are NOT found at plate boundaries, but instead form over hot spots (a weak spot in the normal lithosphere). Flash Animation
Thin magma/lava flows out from a hot spot and forms a low, wide cone.
The Hawaiian Islands are an example of a chain of shield volcanoes.
Rift eruptions - these occur along long cracks in the lithosphere
Not explosive, but release massive amounts of lava.
Found at diverging plate boundaries

12. Assignment Classwork: Chapter 12 Quiz Chapter 12 Review Worksheet
Homework:
Workbook Pages