1. PSC 1515 Chapter 8
Plate Tectonics

2. Earth’s Layers Part 1
Crust
Mantle
Core

3. Earth’s Layers – part 2 Lithosphere Asthenosphere Lower Mantle
Outer Core
Inner Core

4. Continental Drift – a Theory
Once upon a time when the Earth was formed and had developed water and an oxygen atmosphere, the galaxy was enjoying the site of this water covered planet. Then all of the land formed one large continent. This continent was called Pangea.
Slowly, very slowly, Pangea started to break apart. The pieces of the crust drifted across the top of the mantle forming multiple continents

6. Plates The Earth’s crust broke into several sections we call plates
These plates float on the semi liquid mantle
They move in three different ways.
Convergent – move together to make mountains
Divergent – move apart to make trenches
Transform – slide past each other

9. Divergent Boundries Plates pulled apart
Volcanoes create new crust material
Magma fills in the empty space between
Magma comes from athenosphere
Seafloor spreading
Mid Atlantic Ridge
East African Rift Valley

12. Convergent Boundries Two plates move toward each other,
one may move under the other (subducts)
Decrease Earth’s crust
Increase at Divergent = decrease at Convergent
Produces volcanoes and mountains

13. Three kinds of Convergent
Oceanic-oceanic – older plate subducts
Forms ocean trenches – eg. Mariana Trench – 7 miles deep
Inhabited by extremophiles- animals that can live at high temp and pressure. Often use H2S instead of O2
Form volcanic islands like Hawaii
Oceanic-continental – oceanic crust subducts
Forms some mountain ranges
Cascade Range in NW
Continental-continental – same kind of rock
No subduction
Forms mountains like Himalayas

16. Subduction zone

17. Transform Boundries Slide past each other
Lithosphere (crust) neither created nor destroyed
Most found in oceans
Famous – San Andreas Fault

18. Ring of Fire
The Ring of Fire is a string of volcanoes and sites of seismic activity, or earthquakes, around the edges of the Pacific Ocean. Roughly 90% of all earthquakes occur along the Ring of Fire, and the ring is dotted with 75% of all active volcanoes on Earth. 
The Ring of Fire isn’t quite a circular ring. It is shaped more like a 40,000-kilometer (25,000-mile) horseshoe. A string of 452 volcanoes stretches from the southern tip of South America, up along the coast of North America, across the Bering Strait, down through Japan, and into New Zealand. Several active and dormant volcanoes in Antarctica, however, “close” the ring.

19. Volcanoes - Ring of fire

20. Earthquakes – Ring of Fire