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Today’s Quiz
1) Vocabulary Chapter 1b and 12
2) Review Chapters 11
1
Thursday, August 29, 13
Today’s Quiz
1) Vocabulary Chapters 1b and 12
2) Review of Chapter 11
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Plate Tectonics
Chapters 1b and 12
Presidential Palace, Haiti Earthquake
Mw7.0 (2010)
Thursday, August 29, 13
2
Within Earths deep interior, the
transition from solid mantle to liquid
outer core is due to _______________.
a) an increase in the temperature toward the
center of the planet causes the outer core to be
molten.
b) the greater pressure at depth.
c) the metal core has a lower melting temperature
than the silicate rock of the mantle.
d) a combination of greater pressure and greater
depth.
e) don’t know
3
Thursday, August 29, 13
Within Earths deep interior, the
transition from solid mantle to liquid
outer core is due to _______________.
a) an increase in the temperature toward the
center of the planet causes the outer core to be
molten..
b) the greater pressure at depth.
c) the metal core has a lower melting temperature
than the silicate rock of the mantle.
d) a combination of greater pressure and greater
depth.
e) don’t know
4
Thursday, August 29, 13
Within Earths deep interior, the
transition from liquid outer core to a
solid inner core is due to _______________.
a) an increase in the temperature toward the center
of the planet.
b) a decrease in the temperature toward the center
of the planet.
c) a change in the composition of the core.
d) a combination of greater pressure and greater
depth.
e) don’t know
5
Thursday, August 29, 13
Within Earths deep interior, the
transition from liquid outer core to a
solid inner core is due to _______________.
a) an increase in the temperature toward the center
of the planet.
b) a decrease in the temperature toward the center
of the planet.
c) a change in the composition of the core.
d) a combination of greater pressure and greater
depth.
e) don’t know
6
Thursday, August 29, 13
The asthenosphere is capable of
deforming plastically because______
a) the more mafic rocks of the asthenosphere have a lower
melting temperature than the underlying mesosphere.
b) the greater pressure at depth leads to melting.
c) the asthenosphere is mostly a liquid.
d) the temperature of the rocks at asthenospheric depths are
close to the solidus of ultramafic rocks.
e) don’t know
7
Thursday, August 29, 13
The asthenosphere is capable of
deforming plastically because______
a) the more mafic rocks of the asthenosphere have a lower
melting temperature than the underlying mesosphere.
b) the greater pressure at depth leads to melting.
c) the asthenosphere is mostly a liquid.
d) the temperature of the rocks at asthenospheric depths are
close to the solidus of ultramafic rocks.
e) don’t know
8
Thursday, August 29, 13
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Asthenosphere
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Thursday, August 29, 13
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0
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2500
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3500
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4500
Lithosphere
Asthenosphere
l
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l
l
l
l
250
1500
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1000
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Rheology
500
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Gradient
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Depth (km)
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Plate Tectonics?
Chapters 1b and 12
Presidential Palace,
Haiti Earthquake
Mw7.0 (2010)
Thursday, August 29, 13
10
North
Thursday, August 29, 13
What do you see?
North
Thursday, August 29, 13
Compare?
“Plate Tectonic
Theory”
13
Thursday, August 29, 13
Continental Drift hypothesis
+
Sea Floor Spreading hypothesis
+
Vine-Mathews hypothesis
=
“Plate Tectonic Theory”
14
Thursday, August 29, 13
Continental Drift hypothesis
+
Sea Floor Spreading hypothesis
+
Making of a Theory?
Vine-Mathews hypothesis
=
“Plate Tectonic Theory”
14
Thursday, August 29, 13
Alfred Wegener (1880-1930)
“Continental Drift hypothesis” (1915)
15
Thursday, August 29, 13
Alfred Wegener (1880-1930)
“Continental Drift hypothesis” (1915)
16
Thursday, August 29, 13
Alfred Wegener (1880-1930)
“Continental Drift hypothesis” (1915)
Laurasia
PANGEA
Entire
supercontient
Gondwanaland
Super Continent Formation (250 Million Years ago)
17
Thursday, August 29, 13
Alfred Wegener (1880-1930)
“Continental Drift hypothesis” (1915)
Laurasia
What was Wegener’s
PANGEA
Evidence? Entire
supercontient
Gondwanaland
Super Continent Formation (250 Million Years ago)
18
Thursday, August 29, 13
Fit of the Continents
19
Thursday, August 29, 13
Fit of the Continents
20
Thursday, August 29, 13
Fit of the Continents
20
Thursday, August 29, 13
Mountain belts of the World
21
Thursday, August 29, 13
Mountain Belt Continuity
Laurasia
Gondwana
Super Continent Formation (250 Million Years ago)
22
Thursday, August 29, 13
Glacial/Ice Sheet Evidence
23
Thursday, August 29, 13
Glacial/Ice Sheet Evidence
24
Thursday, August 29, 13
Glacial/Ice Sheet Evidence
25
Thursday, August 29, 13
Glacial/Ice Sheet Evidence
26
Thursday, August 29, 13
Wegener’s
Solution
27
Thursday, August 29, 13
Fossil Evidence
Modern Animal Distribution
28
Thursday, August 29, 13
Fossil Evidence
Modern and Ancient Animal Distribution
29
Thursday, August 29, 13
Fossil Evidence
Ancient Distribution
30
Thursday, August 29, 13
Fossil Evidence
Ancient Distribution
Glossopteris
30
Thursday, August 29, 13
Fossil Evidence
Ancient Distribution
Glossopteris
Mesosaurus
30
Thursday, August 29, 13
Fossil Evidence
Ancient Distribution
Glossopteris
Land Bridge
30
Thursday, August 29, 13
Mesosaurus
Fossil Evidence
Ancient Distribution
31
Thursday, August 29, 13
Fossil Evidence
Ancient Distribution
Glossopteris
31
Thursday, August 29, 13
Fossil Evidence
Ancient Distribution
Glossopteris
Mesosaurus
31
Thursday, August 29, 13
Fossil Evidence
Ancient Distribution
Glossopteris
Land Bridge
31
Thursday, August 29, 13
Mesosaurus
Fossil Evidence
Ancient Distribution
32
Thursday, August 29, 13
Fossil Evidence
Ancient Distribution
Glossopteris
32
Thursday, August 29, 13
Fossil Evidence
Ancient Distribution
Glossopteris
Mesosaurus
32
Thursday, August 29, 13
Fossil Evidence
Ancient Distribution
Glossopteris
Land Bridge
32
Thursday, August 29, 13
Mesosaurus
Land Bridge Problem
33
Thursday, August 29, 13
Density and Thickness
34
Thursday, August 29, 13
Density and Thickness
Continental crust
Oceanic crust
34
Thursday, August 29, 13
Density and Thickness
Take Home Message
1) The less dense the crust, the more buoyant it is with
respect to the mantle and the greater elevation it will
“float”. Conversely, the more dense the curst, the
lower it “floats” and thus will have lower elevation.
2) The thicker the crust, the greater its “floating”
elevation and vise versa.
35
Thursday, August 29, 13
Isostacy Revisited
36
Thursday, August 29, 13
Land Bridge Problem
37
Thursday, August 29, 13
If the entire surface of Earth was made of the same stuff such that
the oceans basins are just submerged continental crust elevation
should be normally distributed as shown below?
38
Thursday, August 29, 13
Wegener’s Solution
However, the elevation of Earths
surface is Bimodal (solid line)
indicating that the Earth is
composed of two distinct types
of crust (oceanic and
continental), thereby arguing
against submerged continents
and the existence of land
bridges.
39
Thursday, August 29, 13
Wegener’s Solution
40
Thursday, August 29, 13
Alfred Wegener (1880-1930)
“Continental Drift hypothesis”
41
Thursday, August 29, 13
Last photograph of Wegener
(left). Dies in Greenland
pursuing is hypothesis
Alfred Wegener (1880-1930)
“Continental Drift hypothesis”
By what Process?
41
Thursday, August 29, 13
Last photograph of Wegener
(left). Dies in Greenland
pursuing is hypothesis
Wegener’s missing link
In addition to indicating the
continents and ocean floor are
fundamentally different, the
bimodal distribution indicates
they form by a very different
process.
42
Thursday, August 29, 13
Harry Hess (1906-1969)
“Sea Floor Spreading hypothesis” (1962)
43
Thursday, August 29, 13
Harry Hess (1906-1969)
“Sea Floor Spreading hypothesis” (1962)
What was his Evidence?
44
Thursday, August 29, 13
Harry Hess (1906-1969)
“Sea Floor Spreading hypothesis” (1962)
Observations
1) Topography of the Sea floor suggested the the ocean basins
got older farther from the ridge (Mid Atlantic Ridge, Guyots)
2) If the Ocean floors are 4.5 Billion years old why is there so
little sediment.
3) Why are the oldest fossils found in ocean sediments only
180 Million years old?
45
Thursday, August 29, 13
Harry Hess (1906-1969)
“Sea Floor Spreading hypothesis” (1962)
Observations
1) Topography of the Sea floor
Mid-atlantic ridge
Santa Ynez Mts. Santa Barbara ~1500m (5000’) tall
46
Thursday, August 29, 13
Guyot
Harry Hess (1906-1969)
“Sea Floor Spreading hypothesis” (1962)
Observations
1) Topography of the Sea floor suggested the the ocean basins
got older farther from the ridge (Mid Atlantic Ridge, Guyots)
2) If the Ocean floors are 4.5 Billion years old why is there so
little sediment.
3) Why are the oldest fossils found in ocean sediments only
180 Million years old?
47
Thursday, August 29, 13
Age of the Sea Floor
Youngest
Oldest
48
Thursday, August 29, 13
Harry Hess’ Solution
“Sea Floor Spreading hypothesis” (1962)
49
Thursday, August 29, 13
Harry Hess’ Solution
“Sea Floor Spreading hypothesis” (1962)
50
Thursday, August 29, 13
Depressing Geothermal Gradient with Time
3
51
Thursday, August 29, 13
2
1
Observations
Testing the Hypotheses?
1) Topography of the Sea floor (Mid Atlantic Ridge, Guyots)
2) If the Ocean Floors are 4.5 Billion years old why is there so little
sediment.
3) Why are the oldest fossils found in ocean sediments only 180
Million years old?
52
Thursday, August 29, 13
Fred Vine and Drummond Matthews
“Vine-Matthews hypothesis”(1963)
Assuming that the oceanic crust is indeed made of basalt
intruded in an episodically reversing geomagnetic field,
Drummond H. Matthews of the University of Cambridge and a
research student, Frederick J. Vine, postulated in 1963 that the
new crust would have a magnetization aligned with the field at
the time of its formation. If the magnetic field was normal, as it is
today, the magnetization of the crust would be added to that of
Earth and produce a positive anomaly. If intrusion had taken
place during a period of reverse magnetic polarity, it would
subtract from the present field and appear as a negative
anomaly. Subsequent to intrusion, each new block created at
spreading centre would split and the halves, in moving aside,
would generate the observed bilateral magnetic symmetry.
53
Thursday, August 29, 13
Paleomagnetism?
Thursday, August 29, 13
Methods
Mapping magnetic reversals
55
Thursday, August 29, 13
Methods
Mapping magnetic reversals
55
Thursday, August 29, 13
Sea Floor Spreading video
Thursday, August 29, 13
Magnetic
Anomaly Map
of the Mid
Atlantic Ridge
Symmetrical pattern centered on the ridge
Thursday, August 29, 13
Vine-Matthews hypothesis
confirmed(1963)
58
Thursday, August 29, 13
Vine-Matthews hypothesis
confirmed(1963)
Sea Floor spreading hypotheses
appear to be validated!
58
Thursday, August 29, 13
Vine-Matthews hypothesis
confirmed(1963)
Sea Floor spreading hypotheses
appear to be validated!
What are the Implications?
58
Thursday, August 29, 13
Vine-Matthews hypothesis
confirmed(1963)
Sea Floor spreading hypotheses
appear to be validated!
What are the Implications?
1) Mechanism for Continental Drift!
58
Thursday, August 29, 13
Vine-Matthews hypothesis
confirmed(1963)
Sea Floor spreading hypotheses
appear to be validated!
What are the Implications?
1) Mechanism for Continental Drift!
2) The Earth is broken into tectonic
Plates that are changing relative
positions with time!
58
Thursday, August 29, 13
“Plate Tectonic
Theory
is born”
59
Thursday, August 29, 13
Today’s Quiz
1) Vocabulary Chapters 13
2) Review of Chapter 1b and 12
60
Thursday, August 29, 13