1. Our Amazing Planet

2. Planet Earth Earth’s Layers

3. Crust Earth’s thin outermost layer. – Continental Crust (land) - thick low density rock (granite). – Oceanic Crust (sea floor)- thin dense rock (basalt) ‏

4. Lithosphere Earth’s outermost layer Includes the crust and solid upper part of the mantle. Divided into huge pieces called “Tectonic Plates”. “Floats” on top of the asthenosphere - very hot, soft layer of the mantle.

5. Asthenosphere- Upper Mantle Earth’s thickest layer made of dense iron-rich super heated soft rock. -semisolid layer *Layer where convection currents occur.

6. Convection Currents in the Asthenospere Causes Sea Floor Spreading – The main cause of plate tectonics Convection Currents – Hot magma rises and cooler magma sinks in the Earth’s upper Mantle

8. Core Earth’s innermost layer made of hot, dense iron and nickel. – Outer core - Liquid – Inner core - Solid

9. Earth’s Tectonic Plates

10. Continental Drift – Theory that the Earth’s continents move over time – Proposed by Alfred Wegener in the early 1900’s – Evidence of Continental Drift: Continents fit together (South America and Africa) Similar fossils found on different continents Similar rocks and minerals Similar climatic conditions

11. Continents Fit Together

12. Eastern coast of South America and western coast of Africa

13. Found Fossils!

14. Sea Floor Spreading (divergent boundary) Occurs where tectonic plates spread apart at Mid Ocean Ridges Magma rises from upper mantle creating new crust (sea floor). New “younger” sea floor pushes the existing “older” sea floor out (laterally) explaining why continents move. – Evidence that supports the theory of Continental Drift.

15. Sea Floor Spreading New crust is formed at mid-ocean ridges spreading the sea floor

16. Mid-Atlantic Ridge

18. Rift Valley (divergent boundary) There are only two rift valleys on Earth within continental crust. -the Baikal Rift Valley and the East African Rift. - Tectonic activity splits continental crust much in the same way it does along mid-ocean ridges. As the sides of a rift valley move farther apart, the floor sinks lower.

20. Tectonic Plate Boundaries

21. Convergent Boundaries Tectonic plates that collide or come together A) When two plates of equal density collide they squish together to form folded non volcanic mountains.

22. Convergent Boundaries Subduction Zones (a process) B) Difference in density between oceanic and continental crust creates trenches in the ocean and volcanoes on land

23. Divergent Boundaries Tectonic plates move apart or separate Forms Mid Ocean Ridges in oceans and Rift Valleys on land East African Rift Mid-Atlantic Ridge

24. Mid-Ocean Ridges Chain of volcanoes at the middle of the ocean floor. Causes Sea Floor Spreading Magma comes up from inside the Earth, cools and hardens and creates new sea floor. The rock at the mid-ocean ridge is the youngest and gets older as it moves farther away from the ridges.

25. Mid-Atlantic Ridge

26. Evidence of Pangaea

27. Transform Boundaries Tectonic plates slide past each Forms Fault lines San Andreas Fault in California Why not in Texas?

29. Volcanoes and Earthquakes Most Occur at Tectonic Plate Boundaries

30. Ring Of Fire

31. Ring of Fire Volcanoes around the Pacific Ocean caused by tectonic plates colliding into each other creating subduction zones at CONVERGENT boundaries.