1. Topic 4.1: What ideas, observations, and evidence led to the theory of plate tectonics?

2. Watch the following very informative, very accurate video

3. Draw how you think the continents used to fit together

4. How did you arrive at your answer?

5. Did your drawing look something like this?

6. The Continental Drift Hypothesis
The world used to fit together like a jigsaw puzzle
It was called Pangaea
Pan means “all”
Gaea means “world”

7. What evidence supported this hypothesis?
The outline of the continents looked like they could fit together
Geological information
Ex. similar rocks/mountains found on different continents
Fossil information
Ex. Same species of fossil found on South America and Africa
Climate information
Coal found in Antarctica (made from decomposing living things)

8. So how do scientists know what’s under the surface?
No tools can reach the inner layers of the earth
Scientists use indirect evidence
Measure energy waves during earthquakes
Waves behave differently when they travel through different materials

9. What are the layers of the Earth made of?
Layer of the Earth
Properties
Crust
Thin layer of solid rock
Mantle
Solid layer and soft, plastic like layer
Outer Core
Liquid
Inner Core
Solid

10. In what way does the structure of Earth support the idea that continents can move?

11. Studies of the ocean floor revealed where new rock was made.
By using weighted ropes and later sonar, scientists learned that the ocean floor contained:
Ocean ridges
Underwater mountain ranges
Trenches
Deep, narrow areas in the sea floor

12. Ocean Crust
Ocean rocks are much younger than land rocks because of seafloor spreading. Draw the diagram below in your notes.

13. Describe how the formation of new oceanic crust supports the idea that continents can move.

14. Theory of Plate Tectonics
Earth’s surface is made up of huge slabs of rock called tectonic plates
They float on a layer of fluid-like rock in the mantle
12 major plates and many smaller ones

15. Plate Tectonics Unifying theory that explains:
Events that take place at/or below Earth’s surface
How and why continents move
How and why seafloor spreading occurs
How, why and where earthquakes, volcanoes and formation of mountains occur
Pangea pop-up -