1. Plate Tectonics Introduction
Chapter 9
Plate Tectonics Introduction

2. Earth’s Structure
Earth’s interior consists of three major zones defined by its chemical composition:
Crust
Mantle
Core

3. Crust Thin, rocky outer layer of Earth
The crust is mainly composed of igneous rock
Divided into continental and oceanic
Continental crust is about 5-47 miles thick
Oceanic crust is about 4 miles thick
Crust and upper most part
of the mantle make up the
lithosphere

4. Mantle Solid, rocky shell that extends to a depth of about 1,800 miles
Upper Mantle:
Lithosphere
Rigid
Asthenosphere
Soft, flexible
Lower Mantle

5. Core Sphere composed of iron-nickel alloy Outer core Inner core
Liquid layer is about 1,400 miles thick
Earth’s magnetic field is generated from the flow of metallic iron
Inner core
Radius of about 760 miles
Due to the extreme pressure, the material is solid

6. Continental Drift Hypothesis
A German scientist and meteorologist, Alfred Wegener, proposed a hypotheses:
The continents had once been joined to form a single supercontinent, Pangaea
Pangaea meaning all land

8. Continental Drift Evidence
The Continental Puzzle
Similar coastlines on opposite sides of the ocean
Continents fit together, like a puzzle
Matching Fossils
Fossil organisms found on different landmasses
Rock Types and Structures
Several mountain belts end at one coastline and reappear on a landmass across the ocean
Appalachian Mountains in US, ending off the coast of Newfoundland (Figure 4 on page 251)
Ancient Climates
Glacier evidence, Figure 5 on page 252

9. Matching Mountain Ranges

10. Glacier Evidence

11. A New Theory Emerges…
Wegener could not provide an explanation of exactly what made the continents move
Data on earthquake activity and Earth’s magnetic field became available
By 1968, these findings
led to a new theory,
plate tectonics

12. Plate Tectonics Theory
The upper most mantle and crust, behave as a strong, rigid layer known as the lithosphere
Lithosphere is divided into plates, which move and continually change shape and size
Under the lithosphere, there is a layer of mantle that is super soft (like melted plastic) that the plates float on top of
This layer is called the asthenosphere
7 major plates (pages , Figure 8)
The grinding movements of the plates generate earthquakes, create volcanoes and deform masses of rock into mountains

14. Plate Movements The plates do not just move in one direction
3 Types of Movements
1.Convergent: Coming together
2. Divergent: Moving apart
3. Transform (fault):Sliding past each other
All plates are moving at all times
There are two types of plates:
Continental Plates and Oceanic plates
Each plate could be doing all three motions, just on different sides of the plate
These movements will create the landscapes and mountain ranges that cover the lands and ocean floors, and other hazards that we come in contact with

15. Plate Boundaries Convergent Divergent Transform (fault)
Two plates move together
Divergent
Two plates move apart
Transform (fault)
Two plates slide past each other