The Theory of Plate
Tectonics
And Continental Drift
Essential Questions
► What
is the Theory of Continental Drift?
► What is the Theory of Plate Tectonics?
► What are the names of the plates?
Practical Exercise 1
Supercontinents!
►
If you look at a map of the world, you may notice that some of the
continents could fit together like pieces of a puzzle.
The Birth of a Theory
Earth Revealed Series
► While
watching the video, complete the
worksheet provided. This is to be put into
your portfolio.
► http://www.learner.org/vod/vod_window.ht
ml?pid=316
► 19
mins
Global Tectonics:
Competing Theories
► While
watching the video, complete the
worksheet provided. This is to be placed
into your portfolio.
► http://learning.aliant.net/Player/ALC_Player.
asp?ProgID=VEA_TECTONICS
► 22 mins
Global Tectonics:
Competing Theories
► After
the video, answer the “after the
program” questions. These are due in 1
week.
The Development of the Theory
Wegener’s continental drift hypothesis
stated that the continents had once been
joined to form a single supercontinent.
Wegener proposed that the supercontinent,
Pangaea, began to break apart 200 million
years ago and form the present landmasses.
Wegner proposed this theory in 1912
Breakup of Pangaea
Continental Drift
Evidence
The Continental Puzzle
Matching Fossils
Fossil evidence for continental drift includes
several fossil organisms found on different
•
landmasses.
Rock Types and Structures
Rock evidence for continental exists in the
form of several mountain belts that end at one
coastline, only to reappear on a landmass
across the ocean.
Ancient Climates
Problems With Wegener’s Theory
► No
mechanism for movement of continents
► Wind and currents could possibly move
fossils
► Theory was not accepted by scientists
Continental Drift continued
 A New Theory Emerges
Wegener could not provide an explanation of
exactly what made the continents move.
New technology lead to findings which then
lead to a new theory called plate tectonics.
Testing Plate Tectonics
Evidence for Plate Tectonics
Paleomagnetism is the natural remnant
magnetism in rock bodies; this permanent
magnetization acquired by rock can be used to
determine the location of the magnetic poles at
the time the rock became magnetized.
Normal polarity—when rocks show the same
magnetism as the present magnetism field
Reverse polarity—when rocks show the opposite
magnetism as the present magnetism field
The discovery of strips of alternating polarity, which lie
as mirror images across the ocean ridges, is among the
strongest evidence of seafloor spreading.
Testing Plate Tectonics
continued
Earthquake Patterns
Scientists found a close link between deep-focus earthquakes
and ocean trenches.
The absence of deep-focus earthquakes along the oceanic
ridge system was shown to be consistent with the new theory.
Ocean Drilling
The data on the ages of seafloor sediment confirmed what
the seafloor spreading hypothesis predicted.
The youngest oceanic crust is at the ridge crest, and the
oldest oceanic crust is at the continental margins.
Hot Spots
A hot spot is a concentration of heat in the mantle capable
of producing magma, which rises to Earth’s surface; The Pacific
plate moves over a hot spot, producing the Hawaiian Islands.
Hot spot evidence supports that the plates move over the
Earth’s surface.
Time to Pause…
► Plate
Tectonics Theory assignment.
► Tectonics
 From the Greek tekton, meaning “builder”
 The general term used to describe mountain
building, volcanism, and other processes that
construct geologic features
Ben Franklin, 1782
► Such
changes in the superficial parts of the globe
seemed to me unlikely to happen if the Earth were
solid to the center. I therefore imagined that the
internal parts might be a fluid more dense, and of
greater specific gravity than any of the solids we
are acquainted with, which therefore might swim
in or upon the fluid. Thus the surface of the Earth
would be a shell, capable of being broken and
disordered by the violent movements of the fluid
on which it rested.
Plate Tectonics
► The
Earth’s crust is divided into plates which
move in various directions.
► This plate motion causes them to collide, pull
apart, or scrape against each other.
► Each type of interaction causes a characteristic
set of Earth structures or “tectonic” features.
► The word, tectonic, refers to the deformation
of the crust as a consequence of plate
interaction.
World Plates
Major Plates
► North
American Plate
 covering most of North America, Greenland, Cuba,
Bahamas, and parts of Siberia and Iceland.
 It extends eastward to the Mid-Atlantic Ridge and
westward to the Chersky Range in eastern Siberia.
► Eurasian
Plate
 covering most of North America, Greenland, Cuba,
Bahamas, and parts of Siberia and Iceland.
 It extends eastward to the Mid-Atlantic Ridge and
westward to the Chersky Range in eastern Siberia.
► Pacific
Plate
 is an oceanic tectonic plate beneath the Pacific Ocean
 at 103 million square kilometres it is the largest of all
tectonic plates
Major Plates continued…
► South
American Plate
 includes the continent of South America and also a
sizeable region of the Atlantic Ocean seabed extending
eastward to the Mid-Atlantic Ridge.
► Antarctic
Plate
 includes the continent of Antarctica and extending
outward under the surrounding oceans.
► Australian
Plate
 includes the continent of Australia and surrounding
ocean, and extends northwest to include the Indian
subcontinent and adjacent waters.
► African
Plate
 includes the continent of Africa, as well as oceanic crust
which lies between the continent and various
surrounding ocean ridges.
Minor Plates
► Nazca
Plate
 an oceanic tectonic plate in the eastern Pacific Ocean
basin off the west coast of South America.
► Carribean
Plate
 mostly oceanic tectonic plate underlying Central America
and the Caribbean Sea off the north coast of South
America.
► Cocos
Plate
 is an oceanic tectonic plate beneath the Pacific Ocean
off the west coast of Central America
► Juan
de Fuca Plate
 generated from the Juan de Fuca Ridge
Minor Plates continued…
► Arabian
Plate
 consists mostly of the Arabian peninsula; it extends
northward to Turkey.
► Indian
Plate
 includes the subcontinent of India and a portion of the
basin under the Indian Ocean
► Philippine
Plate
 comprising most of the country of the Philippines.
► Scotia
Plate
 an oceanic tectonic plate
Time to Pause…
► Complete
Names
the worksheet – Tectonic Plate
What are tectonic plates made of?
► Plates
are
made of rigid
lithosphere.
The lithosphere is
made up of the
crust and the upper
part of the mantle.
Plate Movement
► “Plates”
of lithosphere are moved around by
the underlying hot mantle convection cells
How can Earth’s plates move?
► The
plates of the lithosphere float on
the top of the asthenosphere
► Convection currents rise in the
asthenosphere and spread out beneath
the lithosphere
►Geologists
believe this causes plate movement
Practical Exercise 2
Where will “x” be in:
1,000 years?
1,000,000 years?
1,000,000,000 years?