Download Plate Tectonics Intro

Chapter 9

Earth’s interior consists of three major zones
defined by its chemical composition:
 Crust
 Mantle
 Core

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
Solid, rocky shell that extends to a depth
of about 1,800 miles
 Upper Mantle:

 Lithosphere
○ Rigid
 Asthenosphere
○ Soft, flexible

Lower Mantle
Sphere composed of iron-nickel alloy
 Outer 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

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

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

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

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 256-257, Figure 8)
 The grinding movements of the plates
generate earthquakes, create volcanoes and
deform masses of rock into mountains
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

Convergent
 Two plates move together

Divergent
 Two plates move apart

Transform (fault)
 Two plates slide past each other