Earth

1
Table of Contents

• Earths Interior
• Convection and the Mantle
• Drifting Continents
• Sea-Floor Spreading
• The Theory of Plate Tectonics

2
Exploring Inside the Earth
- Earths Interior

• Geologists have used two main types of evidence
  to learn about Earths interior direct evidence
  from rock samples and indirect evidence from
  seismic waves.

3
The Crust
- Earths Interior

• The crust is a layer of solid rock that includes
  both dry land and the ocean floor.

4
The Mantle
- Earths Interior

• Earths mantle is made up of rock that is very
  hot, but solid. Scientists divide the mantle into
  layers based on the physical characteristics of
  those layers.

5
Temperature Inside the Earth
- Earths Interior

• The graph shows how temperatures change between
  Earths surface and the bottom of the mantle. On
  this graph the temperature at the Earths surface
  is 0oC. Study the graph carefully and then answer
  the questions.

6
Temperature Inside the Earth
- Earths Interior

• Reading Graphs
• As you move from left to right on the x-axis, how
  does depth inside the Earth change?

• The depth increases.

7
Temperature Inside the Earth
- Earths Interior

• Estimating
• What is the temperature at the boundary between
  the lithosphere and the asthenosphere?

• About 1,600oC

8
Temperature Inside the Earth
- Earths Interior

• Estimating
• What is the temperature at the boundary between
  the lower mantle and the core?

• About 3,200oC

9
Temperature Inside the Earth
- Earths Interior

• Interpreting Data
• How does temperature change with depth in Earths
  interior?

• It generally increases with depth.

10
The Core
- Earths Interior

• The core is made mostly of the metals iron and
  nickel. It consists of two partsa liquid outer
  core and a solid inner core.

11
Using Prior Knowledge
- Earths Interior

• Before you read, look at the section headings and
  visuals to see what this section is about. Then
  write what you know about Earths interior in a
  graphic organizer like the one below. As you
  read, write what you learn.

What You Know

1. Earths crust is made of rock.
2. Earth is very hot near the center.
3. Dry land is part of the crust.
4. The mantle is very hot.
5. The core contains iron.

What You Learned

1. Geologists use seismic waves to study Earths
   interior.
2. Radioactive substances heat the interior of
   Earth.
3. The crust is thickest under high mountains.
4. The mantle is solid.
5. Movements in the outer core create Earths
   magnetic field.

12
Links on the Structure of Earth
- Earths Interior

• Click the SciLinks button for links on the
  structure of Earth.

13
Types of Heat Transfer
- Convection and the Mantle

• There are three types of heat transfer
  radiation, conduction, and convection.

14
Convection Currents
- Convection and the Mantle

• Heating and cooling of the fluid, changes in the
  fluids density, and the force of gravity combine
  to set convection currents in motion.

15
Convection Currents in Earth
- Convection and the Mantle

• Heat from the core and the mantle itself causes
  convection currents in the mantle.

16
Mantle Convection
- Convection and the Mantle

• Click the Video button to watch a movieabout
  mantle convections.

17
Continental Drift
- Drifting Continents

• Wegeners hypothesis was that all the continents
  were once joined together in a single landmass.

18
Evidence for Continental Drift
- Drifting Continents

• Fossils and rocks found on different continents
  provide evidence that Earths landmasses once
  were joined together in the supercontinent
  Pangaea.

19
Evidence for Continental Drift
- Drifting Continents

• Fossils and rocks found on different continents
  provide evidence that Earths landmasses once
  were joined together in the supercontinent
  Pangaea.

20
Mid-Ocean Ridges
- Sea-Floor Spreading

• The East Pacific Rise is just one of the many
  mid-ocean ridges that wind beneath Earths oceans.

21
What Is Sea-Floor Spreading?
- Sea-Floor Spreading

• In sea-floor spreading, the sea floor spreads
  apart along both sides of a mid-ocean ridge as
  new crust is added. As a result, the ocean floors
  move like conveyor belts, carrying the continents
  along with them.

22
Evidence for Sea-Floor Spreading
- Sea-Floor Spreading

• Several types of evidence supported Hesss theory
  of sea-floor spreading eruptions of molten
  material, magnetic stripes in the rock of the
  ocean floor, and the ages of the rocks themselves.

23
Subduction at Trenches
- Sea-Floor Spreading

• In a process taking tens of millions of years,
  part of the ocean floor sinks back into the
  mantle through deep-ocean trenches.

24
Growing an Ocean
- Sea-Floor Spreading

• Because of sea-floor spreading, the distance
  between Europe and North America is increasing by
  a few centimeters per year.

25
Sea-Floor Spreading
- Sea-Floor Spreading

• Click the Video button to watch a movieabout
  sea-floor spreading.

26
How Plates Move
- The Theory of Plate Tectonics

• The theory of plate tectonics explains the
  formation, movement, and subduction of Earths
  plates.

27
Plate Boundaries
- The Theory of Plate Tectonics

• There are three kinds of plate boundaries
  divergent boundaries, convergent boundaries, and
  transform boundaries. A different type of plate
  movement occurs along each type of boundary.

28
Continental Drift
- The Theory of Plate Tectonics

• It has taken the continents about 225 million
  years since the breakup of Pangaea to move to
  their present locations.

29
Building Vocabulary
- The Theory of Plate Tectonics

• A definition states the meaning of a word or
  phrase by telling about its most important
  feature or function. After you read the section,
  reread the paragraphs that contain definitions of
  Key Terms. Use all the information you have
  learned to write a definition of each Key Term in
  your own words.

Key Terms
Examples
plate
The lithosphere is broken into separate sections
called plates.
The place where two plates move apart, or
diverge, is called a divergent boundary.
scientific theory
A scientific theory is a well-tested concept that
explains a wide range of observations.
A deep valley called a rift valley forms along
the divergent boundary.
plate tectonics
The theory of plate tectonics states that pieces
of Earths lithosphere are in slow, constant
motion, driven by convection currents in the
mantle.
The place where two plates come together, or
converge, is called a convergent boundary.
A transform boundary is a place where two plates
slip past each other, moving in opposite
directions.
fault
Faults are breaks in Earths crust where rocks
have slipped past each other.
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Graphic Organizer

Type of Plate Boundary
Type of Motion
Effect on Crust
Feature(s) Formed
Transform boundary
Plates slide past each other.
Crust is sheared.
Strike-slip fault
Subduction or mountain building
Convergent boundary
Plates move together.
Mountains, volcanoes
Divergent boundary
Mid-ocean ridge, ocean floor
Plates move apart.
Crust pulled apart by tension forces.