Exploring Plate Tectonics: Earth's Crust in Motion

1. Chapter C1: The Changing Earth

2. Lesson 1: What are the Earth’s layers? Lesson 2: How does the Earth’s crust move? Lesson 3: What changes the Earth’s surface? Lesson 4: How do rocks reveal changes on the Earth?

3. Lesson 2: How does the Earth’s crust move? A Discovery. . . • Geographers and cartographers in the 1500s noticed the continents’ edges seemed to fit together like puzzle pieces. • Scientists in the 1900s mapped the edges of the continents (under the oceans) and found that the continents fit together even better.

4. Lesson 2: How does the Earth’s crust move? What do you think?

5. Lesson 2: How does the Earth’s crust move? A hypothesis is formed. . . • Scientists thought maybe the continents were once connected to each other, and have moved apart.

6. Lesson 2: How does the Earth’s crust move? Evidence supports the hypothesis. . . • Fossil deposits • Ancient mountain ranges • Coal deposits • Deposits from glaciers • And more. . .

7. Lesson 2: How does the Earth’s crust move? A theory is born. . . Plate Tectonics • Explains how the continents move • Earth’s crust is divided into 20 sections called plates. • Plates include the crust and the top part of the mantle. • Plates float slowly on the “soupy” middle part of the mantle.

8. Lesson 2: How does the Earth’s crust move? Moving plates. . . 1. Heated mantle rises toward the crust. 2. As it nears the crust, the mantle cools. • Cooling chunks of mantle are pushed aside by heated mantle rising from below. • As the cooled mantle is pushed aside, it drags along the plate floating on top of it. • The cooled chunk of mantle sinks back down, and may be reheated and rise again.

9. Lesson 2: How does the Earth’s crust move? The plates move at about the same speed your fingernails grow!

10. Lesson 2: How does the Earth’s crust move? Volcanoes, earthquakes, and mountains, oh my. . . • The locations of volcanoes, earthquakes, and mountains were identified on maps. • Scientists noticed a pattern. • These locations show us where the edges of the plates can be found. • These edges are called Plate Boundaries.

11. Volcanoes Earthquakes Plate Boundaries Lesson 2: How does the Earth’s crust move? See for yourself. . .

12. Lesson 2: How does the Earth’s crust move? The “Ring of Fire”. . . • Named because of the incredibly large amounts of active volcanoes. • Most of the active volcanoes on Earth are located here!

13. Lesson 2: How does the Earth’s crust move? Plate movement. . . • The plates move in many different directions. • Plate movement causes. . . • New crust formation • Mountains • Volcanoes • Earthquakes

14. Lesson 2: How does the Earth’s crust move? New crust formation. . . • Occurs when plates move away from each other • Crust is formed by hot mantle rising up and then cooling when it reaches the surface.

15. Lesson 2: How does the Earth’s crust move? Mountains. . . • Occur when two plates carrying continental crust collide • Whole mountain ranges form this way. • These mountains continue to grow (by centimeters).

16. Lesson 2: How does the Earth’s crust move? Volcanoes. . . • Occur when a plate carrying heavy ocean crust collides with a plate carrying lighter continental crust • The heavier plate moves below the lighter plate. • The heavy plate begins to melt as temperatures increase. • The melted rock moved to the surface as volcanic eruptions.

17. Lesson 2: How does the Earth’s crust move? Earthquakes. . . • Occur when two plates straining against each other move suddenly • Plates are connected at faults. • Earthquakes range from small and hardly felt to very large and quite damaging.

18. Any Questions?