Download Plate Tectonics 2

Plate Tectonics
A. What are the lines of evidence
Wegener used to support Continental
Drift?
B. What is seafloor spreading? How do
transform faults behave oddly at the
Mid-Ocean Ridge?
C. What was the key development that
led to our current theory of Plate
Tectonics?
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.
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.
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.
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.
In a nutshell...
•“Extraordinary claims require
extraordinary evidence” - Carl
Sagan
Review of Plate Tectonics
• What drives Earth processes?
– gravity and density differences
– external (e.g. hydrologic cycle, erosion)
– internal (e.g. mantle convection)
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)
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)
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)
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)
Plates?
Plate
Questions
Sea floor spreading explains all EXCEPT which of
the following observations:
1. chains of oceanic islands
like Hawaii
2. the young age of oceanic crust
57%
6%
3. increasing age of oceanic crust
away from ridge crests
2%
4. Benioff zone of earthquakes
descending from oceanic trenches
5. Rift valley at mid-ocean ridges
28%
7%
Polarity Question
The portion of the ocean crust nearest the
mid-ocean ridge must have what type
of magnetic polarity?
1. normal
2. reverse
3. none
63%
28%
9%
Estimation Question
•
How many kilometers has India pushed
its way into the soft underbelly of Asia in
the last 55 million years?
1. 2750 cm
6%
2. 2.75 km
18%
3. 275 km
25%
4. 2750 km
37%
5. 2750 m
7%
6. 27500 km
7%
~800 km
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
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?
Continued…
• b) In its travels, Los Angeles won’t
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?