1. Aim: What New Evidence is used to explain Plate tectonics?
Do Now:
What evidence did Wegener and other scientists use to help explain the Theory of Continental Drift?
What new theory emerged? Explain this new theory in your own words.

2. (REVIEW) Theory of Plate Tectonics
1- matching fossils, matching rock types, puzzle piece fit
2- Plate tectonics. The crust is broken into many different pieces (like the shell of a cracked egg). These crustal pieces (plates) carry the continents and is floating on the asthenosphere.

3. I. Earthquakes and Volcanos
What do you notice about the earthquakes and volcanos on this world map?
Boundaries defined by volcanism and seismicity

4. They outline the boundaries of the plates.
I. Earthquakes and Volcanos
Occur in specific areas on our planet and create a pattern around the world.
They outline the boundaries of the plates.

5. This new oceanic crust pushes continents away from each other.
II. Sea-Floor Spreading
Which continents appear to fit best together on the world map? How have these continents moved relative to each other?
as magma rises up through the crust (lithosphere), the sea floor spreads apart and gets wider.
This new oceanic crust pushes continents away from each other.
- rising magma makes new oceanic crust (young)

6. Where would the youngest oceanic crust be located on the diagram?
at the ridge, where new magma rises and solidifies.
Where would the oldest oceanic crust be located on the diagram?
at the edge of the plate closest to the continents
Ridge

8. III. Paleomagnetism (ancient magnets)
Earth’s inner core rotates.
This rotation creates a magnetic field that extends out into space.
The invisible magnetic field…
Protects Earth from solar radiation
Creates a North/South magnetic pole (used by compass)
Can be studied in rocks on Earth’s Surface

9. The iron in the rock shows the record of Earth’s magnetic history.
What minerals make up the core and mantle?
- iron in the rising magma aligns to Earth's magnetic field (like a compass).
- the magma cools and solidifies the iron in place within the rock.
The iron in the rock shows the record of Earth’s magnetic history.

10. Normal polarity - when rocks show the same magnetism as today
~ 1 MYA
~ 500,000 years ago
Present
Normal polarity - when rocks show the same magnetism as today
Reverse polarity - when rocks show the opposite magnetism as today

11. Earth’s Magnetic poles switch about once every 500,000 yrs.
Mid- Ocean Ridge
Earth’s Magnetic poles switch about once every 500,000 yrs.
The magnetic orientation in the rock creates the same pattern on both sides of the boundary.

12. IV. Hot Spots
Fixed concentrations of magma in the mantle that rise to the surface as a plume.
The Hawaiian Islands were formed as the Pacific plate moved over one of these hot spots
Push me

13. Age of sea-floor? Paleomagnetism?
Closure 1:
What if the sea-floor was not spreading?
Evidence that supports sea-floor is spreading
Age of sea-floor?
- sea-floor shows different aged rocks (younger at the ridge and older at the continents)
- sea-floor would have the same age throughout the entire ocean.
Paleomagnetism?
- rocks show matching patterns of alternating magnetism on both sides of the ridge.
- rocks would show the same magnetism

14. Closure 2:
Review Book
Page #1-10