Theory of Plate Tectonics - PowerPoint PPT Presentation

Loading...

PPT – Theory of Plate Tectonics PowerPoint presentation | free to download - id: 6f07a9-YmU0O



Loading


The Adobe Flash plugin is needed to view this content

Get the plugin now

View by Category
About This Presentation
Title:

Theory of Plate Tectonics

Description:

The younger ones were in the center of the ridge. Continental Drift Theory Continental Drift Theory Proposed by Alfred Wegener in 1912 250 million years ago, ... – PowerPoint PPT presentation

Number of Views:66
Avg rating:3.0/5.0
Slides: 49
Provided by: Nicol223
Learn more at: http://classroom.kleinisd.net
Category:

less

Write a Comment
User Comments (0)
Transcript and Presenter's Notes

Title: Theory of Plate Tectonics


1
(No Transcript)
2
Continental Drift Theory
3
(No Transcript)
4
Continental Drift Theory
  • Proposed by Alfred Wegener in 1912
  • 250 million years ago, all of the continents were
    combined into one super-continent called
    Pangaea
  • The continents gradually drifted apart to where
    they are today

5
Puzzle Pieces
  • Continents look like they could be part of a
    giant jigsaw puzzle

6
Distribution of Fossils
  • Plant and animal fossils found on the coastlines
    of different continents

7
Ancient Climates
  • Tropical plant remains (coal deposits) found in
    Antarctica
  • Glaciation in Africa, South America, India, and
    Australia during the same time

8
Sequence of Rocks
  • Same rock patterns found in South America, India,
    Africa, Antarctica and Australia

9
Problems With The Theory
  • Theory was not accepted by scientistswhy?
  • Because Wegner could not identify the cause of
    continental drift

10
Causes of Plate Tectonics/Drifting
11
Convection Currents
  • Hot magma in the Earth moves toward the surface,
    cools, then sinks again.
  • Creates convection currents beneath the plates
    that cause the plates to move.

12
(No Transcript)
13
Heat Transfer The Driving Force of Plate Tectonics
14
Theory of Plate Tectonics
  • Plate Tectonics
  • Plate Boundaries
  • Causes of Plate Tectonics

15
Plate Tectonics
16
What is Plate Tectonics
  • The Earths crust and upper mantle are broken
    into sections called plates
  • Plates move around on top of the mantle like rafts

17
(No Transcript)
18
What is the Lithosphere?
  • The crust and part of the upper mantle
    lithosphere
  • 100 km thick
  • Less dense than the material below it so it
    floats

19
What is the Asthenoshere?
  • The plastisity layer below the lithosphere
    asthenosphere
  • The plates of the lithosphere float on the
    asthenosphere

20
(No Transcript)
21
2 Types of Plates
  • Ocean plates - plates below the oceans
  • Continental plates - plates below the continents

22
Plate Boundaries
23
Divergent Boundaries
  • Boundary between two plates that are moving apart
    or rifting
  • ? ?
  • RIFTING causes SEAFLOOR SPREADING

24
Divergent Boundaries create
  • Mid-ocean ridges
  • rift valleys
  • fissure volcanoes

25
(No Transcript)
26
(No Transcript)
27
Convergent Boundaries
  • Boundaries between two plates that are colliding
  • ? ?
  • There are 3 types

28
Type 1
  • Ocean plate colliding with a less dense
    continental plate
  • Subduction Zone where the more dense plate
    slides under the less dense plate
  • VOLCANOES occur at subduction zones

29
(No Transcript)
30
Andes Mountains, South America
31
Type 2
  • Ocean plate colliding with another ocean plate
  • The more dense plate slides under the less dense
    plate creating a subduction zone called a TRENCH

32
(No Transcript)
33
Aleutian Islands, Alaska
34
Type 3
  • A continental plate colliding with another
    continental plate
  • Have Collision Zones
  • a place where folded and thrust faulted mountains
    form.

35
(No Transcript)
36
(No Transcript)
37
Transform Fault Boundaries
  • Boundary between two plates that are sliding past
    each other
  • EARTHQUAKES along faults
  • Another example of a transform boundary is the
    San Andres Fault

38
(No Transcript)
39
San Andreas Fault, CA
40
Sea-Floor Spreading
41
Introduction
  • Tube Worms - live in the Pacific Ocean about one
    mile deep near the hydrothermal vents.

42
Mapping the mid-ocean ridge
  • The East Pacific Rise has a mid-ocean ridge.
  • Curves around like a baseball.
  • Lies hidden under hundreds of meters of water.

43
Sonar
  • A device that bounces sound waves off underwater
    objects and then records the echoes of these
    sound waves.
  • Sonar mapped mid-ocean ridges.

44
Harry Hess
  • An American geologist who studied mid-ocean
    ridges.
  • He suggested that the ocean floors move like
    conveyor belts, carrying the continents along
    with them.

45
  • At the mid-ocean ridge, molten material rises
    from the mantle and erupts. The molten material
    then spreads out, pushing older rock to both
    sides of the ridge. As the molten material cools,
    it forms a strip of solid rock in the center of
    the ridge. Then more molten material flows into
    the crack.

46
Sea-floor spreading
  • The process that continually adds new material to
    the ocean floor.
  • Evidence molten material, magnetic stripes, and
    drilling samples.

47
Evidence
  • Magnetic Stripes. How does the pattern of
    matching stripes show evidence of sea-floor
    spreading?

48
Evidence 3 - Drilling Samples
  • The Glomar Challenger did a drilling sample and
    found rocks that the farther away from the ridge
    the older the rocks were. The younger ones were
    in the center of the ridge.
About PowerShow.com