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Earth

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Table of Contents Earth s Interior Convection and the Mantle Drifting Continents Sea-Floor Spreading The Theory of Plate Tectonics – PowerPoint PPT presentation

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Title: 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
Lithosphere and Asthenosphere
  • The Lithosphere and Asthenosphere are two layers
    of the Mantle.
  • Lithosphere (Litho means Stone in Greek) is the
    solid rocky upper layer of the mantle. Its about
    100 km (60 miles) thick on average.
  • Asthenosphere (Asthenes means Weak in Greek)
    below the lithosphere this layer is softer and
    flows very slowly.

6
The Earths Magnetosphere
7
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.

8
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.

9
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.

10
Temperature Inside the Earth
- Earths Interior
  • Estimating
  • What is the temperature at the boundary between
    the lithosphere and the asthenosphere?
  • About 1,600oC

11
Temperature Inside the Earth
- Earths Interior
  • Estimating
  • What is the temperature at the boundary between
    the lower mantle and the core?
  • About 3,200oC

12
Temperature Inside the Earth
- Earths Interior
  • Interpreting Data
  • How does temperature change with depth in Earths
    interior?
  • It generally increases with depth.

13
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.

14
Links on the Structure of Earth
- Earths Interior
  • Click the SciLinks button for links on the
    structure of Earth.

15
End of Section Earths Interior
16
Types of Heat Transfer
- Convection and the Mantle
  • There are three types of heat transfer
    radiation, conduction, and convection.

17
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.

18
Convection Currents in Earth
- Convection and the Mantle
  • Heat from the core and the mantle itself causes
    convection currents in the mantle. This is
    believed to power Plate Tectonics -

Video clip
19
Outlining
- Convection and the Mantle
Convection and the Mantle
  • An outline shows the relationship between major
    ideas and supporting ideas. As you read, make an
    outline about heat transfer. Use the red headings
    for the main topics and the blue headings for the
    subtopics.
  • Types of Heat Transfer
  • Radiation
  • Conduction
  • Convection
  • Convection Currents
  • Convection in Earths Mantle

20
More on Convection Currents in the Mantle
- Convection and the Mantle
  • Click the PHSchool.com button for an activity
    about convection currents in the mantle.

21
Mantle Convection
- Convection and the Mantle
  • Click the Video button to watch a movie about
    mantle convections.

22
End of Section Convection and the Mantle
23
Continental Drift
- Drifting Continents
  • Wegeners hypothesis was that all the continents
    were once joined together in a single landmass.

24
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.

25
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.

26
Identifying Supporting Evidence
- Drifting Continents
  • As you read, identify the evidence that supports
    the hypothesis of continental drift. Write the
    evidence in a graphic organizer like the one
    below.

Evidence
Shape of continents
Hypothesis
Earths continents have moved.
Fossils
Climate change
27
Links on Continental Drift
- Drifting Continents
  • Click the SciLinks button for links on
    continental drift.

28
End of Section Drifting Continents
29
Mid-Ocean Ridges
- Sea-Floor Spreading
  • The East Pacific Rise is just one of the many
    mid-ocean ridges that wind beneath Earths oceans.

30
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.

31
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.

32
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. (where is the
    oldest rock found?)

33
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.

34
Sequencing
- Sea-Floor Spreading
  • Make a flowchart to show the process of sea-floor
    spreading.

Magma erupts along mid-ocean ridge.
Magma cools to form new sea floor.
Sea floor spreads away from ridge.
35
More on Sea-Floor Spreading
- Sea-Floor Spreading
  • Click the PHSchool.com button for an activity
    about sea-floor spreading.

36
Sea-Floor Spreading
- Sea-Floor Spreading
  • Click the Video button to watch a movie about
    sea-floor spreading.

37
End of Section Sea-Floor Spreading
38
How Plates Move
- The Theory of Plate Tectonics
  • The theory of plate tectonics explains the
    formation, movement, and subduction of Earths
    plates.

39
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.
    Pages 34 and 35 in text.

40
Calculating a Rate
- The Theory of Plate Tectonics
  • To calculate the rate of plate motion, divide the
    distance the plate moves by the time it takes to
    move that distance.
  • Rate distance/time
  • For example, a plate takes two million years to
    move 156 km. Calculate its rate of motion.
  • 156 km/2,000,000 years 7.8 cm per year
  • Practice Problem
  • The Pacific plate is sliding past the North
    American plate. It has take ten million years for
    the plate to move 600 km. What is the Pacific
    plates rate of motion?
  • 60,000,000 cm 10,000,000 years 6 cm/yr

41
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.

42
Continental Drift Activity
- The Theory of Plate Tectonics
  • Click the Active Art button to open a browser
    window and access Active Art about continental
    drift.

43
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.
44
End of Section The Theory of Plate Tectonics
45
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.
46
End of Section Graphic Organizer
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