1. Sea Floor Spreading and Plate Tectonics
Chapter 1.4 and 1.5

2. Ch. 1.4 Sea-Floor Spreading
Mid-Ocean Ridge
longest chain of mountains in the world
all below the ocean
Scientists use SONAR
to map them
SONAR -a device that records echoes of sound waves
History of Ocean Drilling

3. 2. Sea-floor spreading?
At the mid-ocean ridge, molten material rises from the mantle and erupts. The molten material then spreads out, pushing older rock to both sides of the ridge.
Earth's Volcanic History

4. 3. Scientists found Evidence
Molten Material found
as pillow-shaped rocks
hardened quickly

5. 3 . Scientists found Evidence
Magnetic patterns or stripes found in
Ocean floor rock
Reversals of Earth’s magnetic field

6. 3. 3. Scientists found Evidence
Drilling core samples
age of rock samples
The farther away from the mid-ocean ridge, the older the rocks
Drilling for Cores Samples

7. 4. Subduction at Deep-Ocean Trenches
a process where
the ocean floor
sinks beneath a
deep-ocean trench
and back into
the mantle…
over tens of millions
of years.
Sketch this picture

8. Subduction at Earth’s Oceans
Drilling in the Arctic Ocean

9. Ch. 1.5 Theory of Plate Tectonics
Plate Motion
Pieces of Earth’s lithosphere are in constant slow motion
Driven by convection currents in mantle
Theory of Plate Tectonics explains the
Formation
Movement
Subduction of Earth’s plates

10. Plate Boundaries Plate boundaries are- where edges of lithosphere meet
Faults are- breaks in the crust, where rocks that slip past each other form at plate boundaries

11. 3 Types of Plate Boundaries Transform boundaries
Where 2 plates
slip past each
other

12. Plate boundaries Divergent boundaries
Where 2 plates move apart
A rift (deep) valley forms

13. 2. Plate boundaries Convergent
Where 2 plates come together or collide
The plate density determines which plate goes under-subduction
Where continental crusts collide-it forms mountains

14. Plate boundaries

15. Continent’s Slow Dance
225 million years ago, plates joined together Pangaea
mya Continents split apart,
narrow seas become oceans
135 mya Continents began to drift apart
65 mya India a separate continent,
Australia connected to Antarctica
Today continents look like puzzle pieces that once were together
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