45
02- Die Plattentektonik
02- Die Plattentektonik
02-
Modu
le B
P 1
1R
. Bou
squ
et 2
00
9-2
01
0Geological evidences for continental drift
Baltic shield
Russianplatform
African Foreland
Ger
dnal ne
The fit of the continents around the North Atlantic, after Bullard et al. (1965), and the trends of the Appalachian-Caledonian and Variscan (early and late Paleozoic) fold belts (orange and green respectively).
Correlation of cratons and younger mobile belts across the closed southern Atlantic Ocean
02-
Modu
le B
P 1
1R
. Bou
squ
et 2
00
9-2
01
0Geological evidences for continental drift
Correlation of Permo-Carboniferous glacial deposits, Mesozoic dolerites, and Precambrian anorthosites between the reconstructed continents of Gondwana (after Smith & Hallam, 1970)
02-
Modu
le B
P 1
1R
. Bou
squ
et 2
00
9-2
01
0Geological evidences for continental drift
Correlation of stratigraphy between Gondwana continents (from Hurley, 1968)
02-
Modu
le B
P 1
1R
. Bou
squ
et 2
00
9-2
01
0Paleoclimatological evidences for continental drift
Present distributions of Pangean flora and fauna (from Tarling & Tarling,1971)
02-
Modu
le B
P 1
1R
. Bou
squ
et 2
00
9-2
01
0Paleoclimatological evidences for continental drift
Use of paleoclimatic data to control and confirm continental reconstructions(from Tarling & Tarling, 1971)
02-
Modu
le B
P 1
1R
. Bou
squ
et 2
00
9-2
01
0Continental drift reconstruction
The first mathematical reassembly of continents based solely on geometric criteria was performed by Bullard et al. (1965), who fitted together the continents on eitherside of the Atlantic. This was accomplished by sequentially fitting pairs of continents after determining their best fitting poles of rotation. The only rotation involving parts of the same landmass is that of the Iberian penin- sular with respect to the rest of Europe. This is justified because of the known presence of oceanic lithosphere in the Bay of Biscay which is closed by this rotation. Geologic evidence and information provided by magnetic lineations in the Atlantic indicate that the reconstruction represents the continental configuration during late T r i ass i c/ea r ly Ju rass i c t imes approximately 200 Ma ago.
02-
Modu
le B
P 1
1R
. Bou
squ
et 2
00
9-2
01
0Hot-spots
Wilson, 1963Sketch of the Pacific ocean. Heavy arrow show nine linear chains of islands and seamounts which increase in age in direction of arrow. Single-headed arrows show direction of motion, where known, along large transcurrents faults. Small arrows show postulated direction of flow away from median ridges.
Some possible patterns of convection, showing that, if active volcanos form overrrising vertical currents, chains of extinct volcanoes might be formed by the horizontal flow or the currents. The shaded areas represent stable cores of cells
02-
Modu
le B
P 1
1R
. Bou
squ
et 2
00
9-2
01
0Hot-spots
World map of the main traps (or !ood basalts).Some have been linked to the currently active hot spot volcanoes, whose birth may be the cause of the traps.Active hot spot volcanoes not related to traps
02-
Modu
le B
P 1
1R
. Bou
squ
et 2
00
9-2
01
0Hot-spots
Lithosphere
Plume
Hot spot
Moving of the plateB
Iles AléoutiennesMonts sous-marins de l'Empereur
Chaîne de Hawaii
Midway
Hawaii
< 2 Ma
10 Ma
20 Ma
30 Ma
56 Ma
63 Ma
Océan Pacifique
Moving of the Pacific plate
Monts sous marinsMeiji
140°W160°W180°W20°
30°
40°
50°
20°
30°
40°43 Ma
54 Ma
12 Ma
02-
Modu
le B
P 1
1R
. Bou
squ
et 2
00
9-2
01
0
EPR
S
N
D
D
Mid-Atlantic Ridge
African
superplume
Lower mantle
Melt
(ULVZ)
Outer core
+
+
+
+
+
+ +
+
+
+
+
+
+
+
Inner core
Melt
(ULVZ)
Upper mantle
Cold basin
Tibet
Pacific
superplume
Cold
downwelling
S. America
Hawaii
02-
Modu
le B
P 1
1R
. Bou
squ
et 2
00
9-2
01
0Sea-floor spreading
© Nature Publishing Group1965
26 THE HISTORICAL BACKGROUND
The difference between transcurrent and transform faults, (a) In atranscurrent (or strike-slip) fault, the direction of movement can bedetermined from the offset of a feature intersecting the fault. If thefeature is moved to the left, it is a left-lateral fault, as shown here. Thenorth side of the fault has moved to the left (west), the south side ofthe fault has moved to the right (east), and the fault may continueindefinitely, (b) In a ridge-to-ridge transform fault, a section of themid-ocean ridge is fractured perpendicular to its length. In this case,the right side of the ridge is moving to the right (east), the left side ismoving to the left (west), and the sense of motion is opposite of thatillustrated in (a). Note also that the fault does not extend indefinitely,but terminates against the north-south running ridge segments.
rifting ridge segment. There was no longer any doubt that the oceanswere splitting apart.
Sykes and co-workers Jack Oliver and Bryan Isacks also examined theslip directions on earthquakes associated with the edges of ocean basins.These edges are characterized by zones of deep-focus earthquakes, eitherbeneath volcanic island chains like the Aleutians on the northern edgeof the Pacific, or beneath continental margin mountain belts such as theAndes on the eastern edge of the Pacific. Sykes, Oliver, and Isacks foundthat the slip directions were consistent with the overlap of one crustalplate onto another, with the lower one slipping downward; the zones ofdeep-focus earthquakes marked the position of the down-going slab.44
A global picture now emerged. Oceans split apart at their centers,where new ocean floor is created by submarine volcanic eruptions. The
Wilson, 1965
02-
Modu
le B
P 1
1R
. Bou
squ
et 2
00
9-2
01
0Geometry on a sphere
1962 W. JASON MORGAN
•J
Time I Time 2 Time
Fig. 3. Three crustal blocks bounded by a rise, trench, and faults are shown at three successive time intervals. Note the motion of the four circular markers placed on the ridge cres• at time 1: the solid segments show the motion o,f these circles; the dotted segments show the original coordinates of these markers. The strike of a transform fault is parallel to the difference of the velocities of the two sides; the crest of the ridge drifts with a velocity that is the average of the velocities of the two sides.
vector average of the velocities of the two sides. Note that the two transform faults extending into block 2 on the left are not parallel. All faults north of the trench (between blocks 1 and 2) would run east to, west as the one shown, and all faults south of the trench (between blocks 2 and 3) would have a 45 ø strike as shown. An example of where the strike of transform faults changes in this manner occurs off the coast of Mexico at, the intersection of the Middle Amer- ica trench, the East Pacific rise, and the Gulf of California.
We now go to a sphere. A theorem of geom- etry states that, a block on a sphere can be moved to any other conceivable orientation by a single rotation about a properly chosen axis. We use this theorem to prove that the relative motion of two rigid blocks on a sphere may be described by an angular velocity vector by using three parameters, two to specify the loca- tion of the pole and one for the magnitude of the angular velocity. Consider the left block in Figure 4 to be stationary and the right block to be moving as shown. Fault lines of great dis- placement occur where there is no component of velocity perpendicular to their strike; the strike
of the fault must be parallel to the difference in velocity of the two sides. Thus, all the faults common to these two blocks must lie on small circles concentric about the pole of relative mo- ron.
The velocity of one block relative to another will vary along their common boundary; this
Fig. 4. On a sphere, the motion of block 2 relative to block I must be a rotation about some pole. All faults on the boundary between I and 2 must be small circles concentric about the pole A.
Morgan, 1967
02-
Modu
le B
P 1
1R
. Bou
squ
et 2
00
9-2
01
0
The Euler’s theorem states that the movement of a portion of a sphere across its surface is uniquely defined by a single angular rotation about a pole of rotation.
The pole of rotation, and its antipodal point on the opposite diameter of the sphere, are the only two points which remain in a fixed position relative to the moving portion. Consequently, the movement of a continent across the surface of the Earth to its pre-drift position can be described by its pole and angle of rotation
02-
Modu
le B
P 1
1R
. Bou
squ
et 2
00
9-2
01
0
P
Q
RS
T
Axe de rotation de la Terre
Axe de rotationde la plaque
Plan équatorial dela plaque en rotation
Plaque 1
Plaque 2
Axe de rotation de la Terre
02-
Modu
le B
P 1
1R
. Bou
squ
et 2
00
9-2
01
0
P
A
B
Plate B is moving counter-clockwise relative to plate A.
The motion is defined by the angular velocity ω about the pole of rotation P.
Double lines are ridge segments, and arrows denote direction of motion on transform fault
02-
Modu
le B
P 1
1R
. Bou
squ
et 2
00
9-2
01
0Bücher
A
BCa
bc
(a)A
B
C
a
bc
(b)
sinAa
sinBb
sinCc
a 2 b2 c 2 2bc cos A sinAcos a
sinBcos b
sinCcos c
cos a cos b cos c sin b sin c cos A
02-
Modu
le B
P 1
1R
. Bou
squ
et 2
00
9-2
01
0
urel = ωa sin
where a is the radius of the Earth and ∆ is the angle subtended at the center of the Earth by the pole of rotation P and the point A on the plate boundary
a)
A P
O
a
a
a
a sin
02-
Modu
le B
P 1
1R
. Bou
squ
et 2
00
9-2
01
0
Geographic North
A
s P
b)
O
Equator
Pole of Rotation
cos = cos cos + sin sin cos −
The angle ∆ is related to the colatitude Θ and east longitude Ψ of the rotation pole and the colatitude Ψ’ and east longitude Θ’ of the point on the plate boundary A
02-
Modu
le B
P 1
1R
. Bou
squ
et 2
00
9-2
01
0
Paci!c
Cocos
Caribbea
Juan deFuca
Philippines
Nazca
Scotia
Indian
Arabian
AustralianSouth
America
NorthAmerica
EurasiaEurasia
Africa
Rate in cm/a
Plattenränder
4,1 OzeanKonvergentDivergent
Die Plattentektonik, heutige Model
02-
Modu
le B
P 1
1R
. Bou
squ
et 2
00
9-2
01
0Earth’s magnetism
02-
Modu
le B
P 1
1R
. Bou
squ
et 2
00
9-2
01
0Earth’s magnetism
Declination (magnetic): The angle between magnetic north (as given by the compass needle)and geographic north (in the horizontal plane, counted positive eastward)
Inclination (magnetic): The angle between the magnetic field direction (or the direction of magnetization in a rock) and the local hor izon ta l p lane ( coun ted pos i t i v e downwards, negative upwards). Inclination is zero at the magnetic equator and ±90° (vertical) at the magnetic poles. A simple formula helps to derive magnetic latitudes from magnetic inclination in the case where the field is that of a dipole (which is roughly the case for the Earth)
Magnetic!eld
(vector)
EAST(geographic)
NORTH(magnetic)
NORTH(geographic)
declination
Vertical(downward)
inclination
02-
Modu
le B
P 1
1R
. Bou
squ
et 2
00
9-2
01
0Earth’s magnetism
SN i
S
N
i=0
D
S
N
i
Magneticequator
i: inclinationD: declination
Magneticnorth
Geographicnorth
02-
Modu
le B
P 1
1R
. Bou
squ
et 2
00
9-2
01
0Earth’s magnetism
0
30 N
60 N
30 S
60 S
1800 90 E180 90 W
8580
7570
85
S
0
30 N
60 N
30 S
60 S
(a) InclinationN
0
85
8075
70
50
20
80
70
60
4020
60
40
50
02-
Modu
le B
P 1
1R
. Bou
squ
et 2
00
9-2
01
0Earth’s magnetism
50
30
60
50
50
60
40
25
40
60
0
30 N
60 N
30 S
60 S
1800 90 E180 90 W
0
30 N
60 N
30 S
60 S
(b) Total intensity
02-
Modu
le B
P 1
1R
. Bou
squ
et 2
00
9-2
01
0Earth’s magnetism
The internal structure of the Earth (left side) and the vertical component of the geomagnetic field represented at the surface (top right side) and at the core-mantle boundary (bottom right side), for the epoch 2005.0 (based on the Olsen et al. (2006) model). The core magnetic field is mainly dipolar but the field is modulated by smaller scales. The structure of the vertical component depends on the depth at which the magnetic field is represented, the smaller scales being more apparent at the core-mantle boundary than at the Earth’s surface. For dynamo modelling, the magnetic field is represented at the core-mantle boundary
02-
Modu
le B
P 1
1R
. Bou
squ
et 2
00
9-2
01
0Magnetism on the Earth
Magnetism recorded on land or on sea is showing different patterns:- fine and regular in the oceans- irregular and coarse on the continent
02-
Modu
le B
P 1
1R
. Bou
squ
et 2
00
9-2
01
0Paleomagnetism
geomagneticfield direction
magnetitegra ins
wa ter
sediment
water
magnetitegrains
Curiepoint
ferromagnetism paramagnetism
Magnetization
Temperature
magnetitegrain
magnetizationdirection
matrixmineral
fielddirection
Igneous rocks Sedimentary rocks
Recording of the Earth’s magnetism within rocks
02-
Modu
le B
P 1
1R
. Bou
squ
et 2
00
9-2
01
0Paleomagnetism
dipole field line
Dipole axis
horizontal
rEquator
tan I = 2 tan
I
(a)
(b) The inclinations measured in modern deep- sea sediment cores agree well with the theoretical curve (based on data from Schneider and Kent, 1990).
(a) The geocentric axial dipole hypothesis predicts the relationship tan I =2tan λ between the inclination I of a dipole field and the magnetic latitude λ.
(b)
Latitude,
Site
mea
nin
clin
atio
n, I
60
60
30
30
90
6003°06- 09°03--90°
tan I = 2 tan
90
02-
Modu
le B
P 1
1R
. Bou
squ
et 2
00
9-2
01
0Paleomagnetism
Plio-Pleistocene to Recent paleomagnetic poles (younger than 5 Ma)
Present-day geomagnetic pole
180
90 09W E
0
50 N
The direction of the Earth’s magnetic field for two declination series, Paris and London.
Paleomagnetic pole positions for rocks of Plio-Pleistocene to Recent age (after McElhinny, 1973)
02-
Modu
le B
P 1
1R
. Bou
squ
et 2
00
9-2
01
0Paleomagnetism
1 1
22
3
3
4
4
5
5
6
6
7
7
8
8
9
9
10
10
11
11
12
13
14
Single continentSutured continent
Rifting
A
A
A + B
B
B
Divergence
Con
verg
ence
70
0180
90 W
90 E
EuropeanAPW
50
30
350300 250
200
100
350
300 250
200
150100
50
50
150
NorthAmericanAPW
02-
Modu
le B
P 1
1R
. Bou
squ
et 2
00
9-2
01
0Paleomagnetism
E quator
30S
60S
545
417
443
495
352
290
24814220665
060 E
550
Ordovician
Cambrian
Silurian
Devonian
Carboniferous
Permian
Triass ic
C retac
eous
Jura s
000 E
02-
Modu
le B
P 1
1R
. Bou
squ
et 2
00
9-2
01
0Paleomagnetism
_European paleomagnetic poles:Pliocene and PleistocenePermian
90 E90 W
0
180
75 N
60 N
45 N
02-
Modu
le B
P 1
1R
. Bou
squ
et 2
00
9-2
01
0Paleomagnetic scale
VGPlatitude
90 N90 S 0
polaritytransitions
excursion
polaritysubchron
norm
alpo
larit
y chr
onre
vers
epo
larit
y chr
on
normal Polarity: reverse transitional
Polarityinterpretation
02-
Modu
le B
P 1
1R
. Bou
squ
et 2
00
9-2
01
0Paleomagnetic scale
normal polarity
reverse polarity
Co
x e
t al.
, 1
96
3
Co
x e
t al.
, 1
96
4
Do
ell
&
Da
lry
mp
le,
19
66
Ch
am
ala
un
, 1
96
6
Op
dy
ke,
19
72
Events Epochs
Jaramillo
Olduvail
Kaena
Mammoth
Cochiti
Thvera
Sidufjall
Nunivak
Brunhes
normal
Matuyama
reversed
Gauss
normal
Gilbert
reversed
Epoch 5
normal
1
2
3
4
5
6
0
1
2
3
4
5
6
0
Ag
e (
Ma
)
Ag
e (
Ma
)
& lla
gu
oD
cM C
ox
et
al.
, 1
96
8
02-
Modu
le B
P 1
1R
. Bou
squ
et 2
00
9-2
01
0Paleomagnetism
0
0100200300 100 200 300
246 2 4 6
+500
-500
Gilbertinverse Ga
uss n
orm
al
Gaus
s nor
mal
Mat
uyam
a inv
erse
Mat
uyam
a inv
erse
Brunhesnormal
Gilbertnormal
Age (Ma)
Eau de mer
SédimentsBasaltes et gabbros
océaniques
Lithosphère
Asthénosphère
nT
Distance (km)
02-
Modu
le B
P 1
1R
. Bou
squ
et 2
00
9-2
01
0Paleomagnetism vs. age in oceans
02-
Modu
le B
P 1
1R
. Bou
squ
et 2
00
9-2
01
0Paleomagnetism & plate movement
02-
Modu
le B
P 1
1R
. Bou
squ
et 2
00
9-2
01
0Paleomagnetism
110–150
40
80
200
80
40
120
160
80 40
120 160–200
True
Polar
Wander
Hotspot
Apparent
Polar Wander
Paleomagnetic
Apparent
Polar Wander
60
30
60
30
60
30
(a)
(b)
(c)
01
-Geo
dyn
am
ik u
nd T
ekto
nik
R.
Bou
squ
et 2
00
9-2
01
0
Superkontinent Pangea
Vor 200 Millionen Jahren
01
-Geo
dyn
am
ik u
nd T
ekto
nik
R.
Bou
squ
et 2
00
9-2
01
0Vor 70 Millionen Jahren
01
-Geo
dyn
am
ik u
nd T
ekto
nik
R.
Bou
squ
et 2
00
9-2
01
0Vor 50 Millionen Jahren
01
-Geo
dyn
am
ik u
nd T
ekto
nik
R.
Bou
squ
et 2
00
9-2
01
0Vor 20 Millionen Jahren
01
-Geo
dyn
am
ik u
nd T
ekto
nik
R.
Bou
squ
et 2
00
9-2
01
0Heute
02-
Modu
le B
P 1
1R
. Bou
squ
et 2
00
9-2
01
0
Paci!c
Cocos
Caribbea
Juan deFuca
Philippines
Nazca
Scotia
Indian
Arabian
AustralianSouth
America
NorthAmerica
EurasiaEurasia
Africa
Rate in cm/a
Plattenränder
4,1 OzeanKonvergentDivergent
Die Plattentektonik, heutige Model
