Prentice Hall EARTH SCIENCE

1
Prentice Hall EARTH SCIENCE

• Tarbuck Lutgens

?
2
Chapter 9
Plate Tectonics
3
Alfred LothAr Wagner

• German climatologist and geophysicist.
• Born in 1880 Died in 1930
• Created the Continental Drift Hypothesis
• Published his idea in his book entitled
  The Origin of
  Continents and Oceans in 1912
• His idea was well supported into the 1960s
  and his book was used as a
  standard school
  textbook in Germany.
• Interesting Facts! He received a Ph.D. in
  Astronomy from the University of Berlin. He was
  drafted into the army after earning his degree,
  but was injured and therefore served out his time
  forecasting the weather which lead him studying
  meteorology to geology, through paleoclimatology
  the study of ancient weather.

4
9.1 Continental Drift
? Wegeners continental drift hypothesis
continents had once been joined forming a
supercontinent.
Wegener proposed that the supercontinent,
Pangaea, began to break apart 200 million years
ago and form the present landmasses. The body of
water (or superocean) Panthalassa covered the
rest of the earth.
5
Breakup of Pangaea
2nd part of his hypothesis About 200 million
years ago Pangaea began breaking into two
(Laurasia and Gondwanaland) and formed the Tethys
Sea.
Use your book page 250 to label the diagrams.
6

• USE PAGE 250 IN YOUR TEXTBOOK TO LABEL THE
  PICTURES ON YOUR HANDOUT.

7
9.1 Continental Drift
? Evidence
1. Matching Coastlines coastlines match Biggest
argument to this evidence coastlines fit
together like puzzle pieces
8
9.1 Continental Drift
? Evidence

• Matching Fossils
• Example Mesosaurus an aquatic reptile
• Previously used Explanation for this? He swam
  there?

• Fossil evidence for continental drift includes
• several fossil organisms found on different
• landmasses.

9
9.1 Continental Drift
? Evidence
3. Rock Types and Structures
- mountain belts that end at one coastline, only
to reappear on a landmass across the ocean.
10
Matching Mountain Ranges
Examples? The Appalachian Mountain Belt When
Eastern US, Newfoundland, and the British Isles
are lined up the mountains form a continuous
belt. Hum?
11
9.1 Continental Drift
? Evidence
4. Ancient Climates

• Wegner found glacial deposits showing between 220
  million and 300 million years ago, ice sheets
  covered large areas of the Southern Hemisphere.
• Glacial till (piles of rocks left by glaciers)
  were found in southern Africa and South America,
  as well as India and Australia.

• Glacial striations (scratches and grooves left
  behind from glaciers) This doesnt make sense
  these existed in equatorial areas where the
  climate is too warm for glaciers!

12
Glacier Evidence
13
9.1 Continental Drift
? A New Theory Emerges

• Wegener could not provide an explanation of
  exactly what made the continents move, so despite
  his evidence to support the continental drift
  theory, many geologists rejected it. ?

• Wegeners idea about what made the continents
  move land masses ripped through the ocean crust
  in order to move.

• New technology allowed scientists to map the
  ocean floor and discover the Mid Atlantic Ridge.

• By 1968 these findings led to a new theory called
  Plate Tectonics which explained why the
  continents moved.

14
9.2 Plate Tectonics
? According to the plate tectonics theory, the
uppermost mantle, along with the overlying crust,
behaves as a strong, rigid layer. This layer is
known as the lithosphere.
A plate is one of numerous rigid sections of
the lithosphere that move as a unit over the
material of the asthenosphere.
15
9.2 Plate Tectonics
? Divergent boundaries (also called spreading
centers) are the place where two plates move
apart.
? Convergent boundaries form where two plates
move together.
? Transform fault boundaries are margins where
two plates grind past each other without the
production or destruction of the lithosphere.
16
Three Types of Plate Boundaries