Plate Tectonics

1
Plate Tectonics

• What are the lines of evidence Wegener used to
  support Continental Drift?
• What is seafloor spreading? How do transform
  faults behave oddly at the Mid-Ocean Ridge?
• What was the key development that led to our
  current theory of Plate Tectonics?

2
(No Transcript)
3
(No Transcript)
4
(No Transcript)
5
(No Transcript)
6
(No Transcript)
7
(No Transcript)
8
Drift Rejection Question

• It shows that science is based much off logic and
  reason, and if a "proof" can not be logically
  proved, then it can be rejected regardless if it
  is true or false.

9
Drift Rejection Question

• It shows that without enough evidence, only
  guesses can be made about why things occur. The
  scientists just didn't have enough evidence that
  could explain why things were the way they were.
  Now days we have satellites, and submersibles and
  other types of data collecting devices which
  helps us see the bigger picture.

10
Drift Rejection Question

• It shows that through proving things wrong,
  scientists are getting closer to the truth.
  Wegener had hypotheses that were eventually
  proved wrong, but knowing that those hypotheses
  are wrong narrows down the answers to the correct
  answer.

11
Drift Rejection Question

• The story indicates that science is a complex
  subject in itself and when one hypothesizes about
  something they must have evidence to support what
  their findings and results show. There has to be
  plausible explanation as to why the hypothesis
  makes sense ... however, that's only a start and
  a lot more has to be proven before the hypothesis
  is accepted as a theory.

12
In a nutshell...

• Extraordinary claims require extraordinary
  evidence - Carl Sagan

13
Review of Plate Tectonics

• What drives Earth processes?
• gravity and density differences
• external (e.g. hydrologic cycle, erosion)
• internal (e.g. mantle convection)

14
Plate Boundaries

• divergent (AKA constructive)
• transform
• convergent (AKA destructive)
• ocean-ocean (e.g. Mariana Islands)
• ocean-continent (e.g. Pacific-North America)
• continent-continent (e.g. India-Asia)

15
Examples

• divergent (e.g. mid-Atlantic ridge)
• transform (e.g. San Andreas fault zone)
• convergent
• ocean-ocean (e.g. Pacific-Pacific near Marianas
  Islands)
• ocean-continent (e.g. Pacific-North America)
• continent-continent (e.g. India-Asia)

16
(No Transcript)
17
Examples

• divergent (e.g. mid-Atlantic ridge)
• transform (e.g. San Andreas fault zone)
• convergent
• ocean-ocean (e.g. Pacific-Pacific near Marianas
  Islands)
• ocean-continent (e.g. Pacific-North America)
• continent-continent (e.g. India-Asia)

18
(No Transcript)
19
Examples

• divergent (e.g. mid-Atlantic ridge)
• transform (e.g. San Andreas fault zone)
• convergent
• ocean-ocean (e.g. Pacific-Pacific near Marianas
  Islands)
• ocean-continent (e.g. Pacific-North America)
• continent-continent (e.g. India-Asia)

20
(No Transcript)
21
(No Transcript)
22
Plates?
23
(No Transcript)
24
Questions

• Sea floor spreading explains all EXCEPT which of
  the following observations
• chains of oceanic islands
• like Hawaii 57
• the young age of oceanic crust 6
• increasing age of oceanic crust
• away from ridge crests 2
• Benioff zone of earthquakes
• descending from oceanic trenches 28
• Rift valley at mid-ocean ridges 7

25
(No Transcript)
26
Polarity Question

• The portion of the ocean crust nearest the
  mid-ocean ridge must have what type of magnetic
  polarity?
• normal 63
• reverse 28
• none 9

27
(No Transcript)
28
Estimation Question

• How many kilometers has India pushed its way into
  the soft underbelly of Asia in the last 55
  million years?
• 2750 cm 6
• 2.75 km 18
• 275 km 25
• 2750 km 37
• 2750 m 7
• 27500 km 7

29
(No Transcript)
30
Estimation Question

• How many kilometers has India pushed its way into
  the soft underbelly of Asia in the last 40
  million years?
• 55,000,000 yr x 5cm/yr x 1m/100cm x 1km/1000m
  2750 km

31
(No Transcript)
32
Another one

• Los Angeles is on the west side of the main San
  Andreas fault system. Movement along the fault is
  carrying LA northwest (with respect to North
  America) at a rate of approximately 3 cm/year.
• a) Assuming that the motion will continue in the
  same direction and at the same rate for the next
  300 million years or so, how many kilometers will
  Los Angeles have traveled in 27 million years?

33
Continued

• b) In its travels, Los Angeles wont collide with
  anything for about 4000 km. How far in the future
  will this be?
• c) When it does collide, who will be the lucky
  owners of a new accreted terrane?

34
(No Transcript)
35
(No Transcript)