1. Developing the Theory of Plate Tectonics!
The Game

2. Mapping The Ocean Floor
After WWII scientists began exploring the seafloor in greater detail. They were able to determine the depth of the ocean using a device called a(n):
Echo Sounder

3. Mapping The Ocean Floor
Scientists used the Echo Sounder to determine the depth of the ocean floor. They used this data to create a(n) ______________ map of the sea floor
Topographic

4. Mapping The Ocean Floor
These new topographic maps of the seafloor revealed that vast mountain ranges stretched for many miles deep below the ocean’s surface. The mountain ranges in the middle of the oceans are called _____________________ ridges
Mid-ocean

5. Seafloor spreading Seafloor Spreading
By the 1960’s scientists discovered a new process that helped explain continental drift. __________________ is the process by which new oceanic crust forms along a mid-ocean ridge and older oceanic crust moves away from the ridge.
Seafloor spreading

6. When the seafloor spreads, the mantle below melts and forms _________
Seafloor Spreading
When the seafloor spreads, the mantle below melts and forms _________
magma

7. Seafloor Spreading
Because magma is [more/less] dense than solid mantle, it rises through the cracks in the crust along the mid-ocean ridge

8. When magma erupts on Earth’s surface it is called:
Seafloor Spreading
When magma erupts on Earth’s surface it is called:
lava

9. Basalt Seafloor Spreading
As this lava cools and crystallizes on the seafloor, it forms a type of rock called ________
Basalt

10. Pillow lava Seafloor Spreading
Because the lava erupts into water, it cools rapidly and forms rounded structures called ______________________.
Pillow lava

11. Mid-ocean ridge Seafloor Spreading
As the seafloor continues to spread apart, the older oceanic crust moves away from the _________________ where new crust is being formed.
Mid-ocean ridge

12. Next to the mid-ocean ridge
Seafloor Spreading
Where can the youngest oceanic crust be found?
Next to the mid-ocean ridge

13. Wegener Seafloor Spreading
The idea that seafloor spreading that explains continental drift was proposed by:
Wegener

14. Topography of the Seafloor
The mid-ocean ridge system can form in 2 different ways. What are these?
1) Large amounts lava erupt from
Center of ridge, cool and build up around ridge
2) As lava cools and forms new crust it cracks
The rocks move up or down along these cracks
In the sea floor forming jagged mountain ranges

15. Topography of the Seafloor
Why is it much flatter further away from the mid-ocean ridge
Sediment settles on sea floor

16. Topography of the Seafloor
The theory of seafloor spreading provides a way to explain what?
How continents move

17. outer Magnetic Reversals
Recall that the iron-rich, liquid __________ core is like a giant magnet.
outer

18. Normal Polarity Magnetic Reversals
Today’s magnetic field is described as having __________________ - a state in which magnetized objects, such as compass needles, will orient themselves to point north
Normal Polarity

19. Magnetic Reversals A state in which magnetized objects would
What is reversed polarity?
A state in which magnetized objects would
reverse direction and orient themselves
To point south

20. Hundred thousand, million
Magnetic Reversals
Magnetic reversals occur every few _____________ to every _________ years
Hundred thousand, million

21. Rocks Reveal Magnetic Signature
________ on the seafloor contains iron-rich minerals that are magnetic. Each mineral acts like a small magnet!
Basalt

22. Rocks Reveal Magnetic Signature
Magnetic minerals align themselves with Earth’s magnetic field. When lava erupts from a vent along a mid-ocean ridge, it cools and ___________
Crystallizes

23. Evidence to Support the Theory
How did scientists prove the theory of seafloor spreading?