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Transcript of VL Geodynamik & Tektonik, WS 080921.01.2009 Plattentektonik Institut für Geowissenschaften...
VL Geodynamik & Tektonik, WS 080921.01.2009
PlattentektonikPlattentektonik
Institut für Geowissenschaften Universität Potsdam
VL Geodynamik & Tektonik, WS 0809
Übersicht zur Vorlesung
VL Geodynamik & Tektonik, WS 0809
Plattentektonik
3 Typen von Plattengrenzen
Ozeane Kontinente
VL Geodynamik & Tektonik, WS 0809
VL Geodynamik & Tektonik, WS 0809Earth’s PlatesEarth’s Plates
VL Geodynamik & Tektonik, WS 0809
Divergent boundaries are located Divergent boundaries are located mainly along oceanic ridgesmainly along oceanic ridges
VL Geodynamik & Tektonik, WS 0809
Divergent plate boundariesDivergent plate boundaries
Oceanic ridges and seafloor spreading Seafloor spreading occurs along the oceanic
ridge system
Spreading rates and ridge topography Ridge systems exhibit topographic differences Topographic differences are controlled by
spreading rates
VL Geodynamik & Tektonik, WS 0809
Ridge morphologyRidge morphology
Faster spreading ridges are characterized by more volcanism smoother topography - less faulting fewer moderate earthquakes
Slower spreading ridges are characterized by less volcanism rough topography - more extension by faulting more moderate sized earthquakes
The differences are related to temperature.
VL Geodynamik & Tektonik, WS 0809
Divergent plate boundariesDivergent plate boundaries
Spreading rates and ridge topography Topographic differences are controlled by
spreading rates– At slow spreading rates (1-5 centimeters per year), a
prominent rift valley develops along the ridge crest that is wide (30 to 50 km) and deep (1500-3000 meters)
– At intermediate spreading rates (5-9 cm per year), rift valleys that develop are shallow with subdued topography
VL Geodynamik & Tektonik, WS 0809
Divergent plate boundariesDivergent plate boundaries
Spreading rates and ridge topography Topographic differences are controlled by
spreading rates– At spreading rates greater than 9 centimeters per
year no median rift valley develops and these areas are usually narrow and extensively faulted
Continental rifts Splits landmasses into two or more smaller
segments
VL Geodynamik & Tektonik, WS 0809
Divergent plate boundariesDivergent plate boundaries
Continental rifts Examples include the East African rifts valleys
and the Rhine Valley in northern Europe Produced by extensional forces acting on the
lithospheric plates Not all rift valleys develop into full-fledged
spreading centers
VL Geodynamik & Tektonik, WS 0809
The East African rift – The East African rift – a divergent boundary on landa divergent boundary on land
VL Geodynamik & Tektonik, WS 0809
Convergent plate boundariesConvergent plate boundaries
Older portions of oceanic plates are returned to the mantle in these destructive plate margins
Surface expression of the descending plate is an ocean trench
Called subduction zones Average angle at which oceanic lithosphere
descends into the mantle is about 45
VL Geodynamik & Tektonik, WS 0809
Convergent plate boundariesConvergent plate boundaries
Although all have the same basic charac-teristics, they are highly variable features
Types of convergent boundaries Oceanic-continental convergence
– Denser oceanic slab sinks into the asthenosphere
VL Geodynamik & Tektonik, WS 0809
Convergent plate boundariesConvergent plate boundaries
Types of convergent boundaries Oceanic-continental convergence
– As the plate descends, partial melting of mantle rock generates magmas having a basaltic or, occasionally andesitic composition
– Mountains produced in part by volcanic activity associated with subduction of oceanic lithosphere are called continental volcanic arcs (Andes and Cascades)
VL Geodynamik & Tektonik, WS 0809
An oceanic-continental convergent An oceanic-continental convergent plate boundaryplate boundary
VL Geodynamik & Tektonik, WS 0809
Convergent plate boundariesConvergent plate boundaries
Types of convergent boundaries Oceanic-oceanic convergence
– When two oceanic slabs converge, one descends beneath the other
– Often forms volcanoes on the ocean floor– If the volcanoes emerge as islands, a volcanic island
arc is formed (Japan, Aleutian islands, Tonga islands)
VL Geodynamik & Tektonik, WS 0809
An oceanic-oceanic convergent An oceanic-oceanic convergent plate boundaryplate boundary
VL Geodynamik & Tektonik, WS 0809
Convergent plate boundariesConvergent plate boundaries
Types of convergent boundaries Continental-continental convergence
– Continued subduction can bring two continents together
– Less dense, buoyant continental lithosphere does not subduct
– Result is a collision between two continental blocks – Process produces mountains (Himalayas, Alps,
Appalachians)
VL Geodynamik & Tektonik, WS 0809
A continental-continental convergent A continental-continental convergent plate boundaryplate boundary
VL Geodynamik & Tektonik, WS 0809
The collision of India and Asia The collision of India and Asia produced the Himalayasproduced the Himalayas
VL Geodynamik & Tektonik, WS 0809
Transform fault boundariesTransform fault boundaries
The third type of plate boundary Plates slide past one another and no new
lithosphere is created or destroyed Transform faults
Most join two segments of a mid-ocean ridge as parts of prominent linear breaks in the oceanic crust known as fracture zones
VL Geodynamik & Tektonik, WS 0809
Transform fault boundariesTransform fault boundaries
VL Geodynamik & Tektonik, WS 0809East Pacific Rise west of Costa Rica
VL Geodynamik & Tektonik, WS 0809
Transform fault boundariesTransform fault boundaries
Transform faultsA few (the San Andreas fault and the
Alpine fault of New Zealand) cut through continental crust
VL Geodynamik & Tektonik, WS 0809
Transform Margin
VL Geodynamik & Tektonik, WS 0809
Testing the plate tectonics modelTesting the plate tectonics model
Paleomagnetism Ancient magnetism preserved in rocks at the
time of their formation Magnetized minerals in rocks
– Show the direction to Earth’s magnetic poles – Provide a means of determining their latitude of
origin
VL Geodynamik & Tektonik, WS 0809
•Dip of needle = inclination
•When a rock cools below the Curie point, the magnetization direction is locked in
•We can determine the “paleolatitude”
•Also used in archeology
VL Geodynamik & Tektonik, WS 0809
VL Geodynamik & Tektonik, WS 0809
PaleomagnetismPaleomagnetismThe measurement of remnant magnetism can provide information important information about where a rock may have come from.
Measuring a paleomagnetic direction:
•An individual lava flow may not record an “average” pole (secular variation), so samples from a series of flows may be taken
•Oriented (azimuth and dip) rock cores separated by up to a few meters are drilled (using non-magnetic equipment).
•If the rock has been tilted since its formation, this has to be measured.
•The magnetization direction is measured (by measuring all three axis of the core) using a very sensitive magnetometer.
•The direction, which is relative to the cylinder is calculated with respect to north and the vertical.
•The magnetization direction is plotted on a stereonet.
VL Geodynamik & Tektonik, WS 0809
PaleomagnetismPaleomagnetism• Magnetic inclination varies from
vertical in the center to horizontal at the circumference.
• Declination is the angle around the circle clockwise from north.
• Downward magnetizations (positive inclination) are plotted as open circle. Negative magnetizations are plotted as solid circles.
• Plot mean direction and 95% confidence interval (95% probability of containing the true direction).
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VL Geodynamik & Tektonik, WS 0809
MagnetostratigraphyMagnetostratigraphy•By measuring the polarity of magnetization of a rock of know age (radiometric data, sediment on ocean floor above basement) we can build up a magnetic polarity timescale.
•At even smaller scales we can examine secular variation within a series of lava flow (assuming a high resolution series of flows).
•If these flows are historic, we could probably date them.
•If they are very old, we could use the pattern of secular variation to correlate between outcrops.
•Archeological applications – dating ancient fireplaces.
•The resultant magnetic timescale can be used to date sediments and the seafloor by the recognition of distinctive reversal patterns.
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VL Geodynamik & Tektonik, WS 0809
Geomagnetic ReversalsGeomagnetic Reversals
The first comprehensive magnetic study was carried out off the Pacific coast of North America.
Researchers discovered alternating strips of high- and low- intensity magnetism.
In 1963 Vine and Matthews demonstrated that stripes of high intensity magnetism formed when the Earth’s magnetic field was in the present direction, and stripes of low intensity magnetism formed when the Earth’s magnetic field was in the reversed direction.
VL Geodynamik & Tektonik, WS 0809
A scientific revolution beginsA scientific revolution begins
During the 1950s and 1960s technological strides permitted extensive mapping of the ocean floor
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VL Geodynamik & Tektonik, WS 0809
A scientific revolution beginsA scientific revolution begins
An Extensive oceanic ridge system was discovered.
Part of this system is the Mid-Atlantic Ridge.
A central valley shows us that tensional forces are pulling the ocean crust apart at the ridge crest.
High heat flow. Volcanism.
VL Geodynamik & Tektonik, WS 0809
A scientific revolution beginsA scientific revolution begins
Deep earthquakes showed that tectonic activity was taking place beneath the deep trenches.
Flat topped seamounts were discovered hundreds of meters below sea level.
Dredges of rocks from the seafloor did not recover any rocks older than 180 million years old.
Sediment thickness on the seafloor was much less than expected (the seafloor being younger than expected).
VL Geodynamik & Tektonik, WS 0809
Testing the plate tectonics modelTesting the plate tectonics model
Paleomagnetism Polar wandering
– The apparent movement of the magnetic poles illustrated in magnetized rocks indicates that the continents have moved
– Polar wandering curves for North America and Europe have similar paths but are separated by about 24 of longitude
– Different paths can be reconciled if the continents are place next to one another
VL Geodynamik & Tektonik, WS 0809
Apparent polar-wandering paths for Apparent polar-wandering paths for Eurasia and North AmericaEurasia and North America
VL Geodynamik & Tektonik, WS 0809
Testing the plate tectonics modelTesting the plate tectonics model
Magnetic reversals and seafloor spreading Earth's magnetic field periodically reverses
polarity – the north magnetic pole becomes the south magnetic pole, and vice versa
Dates when the polarity of Earth’s magnetism changed were determined from lava flows
VL Geodynamik & Tektonik, WS 0809
Testing the plate tectonics modelTesting the plate tectonics model
Magnetic reversals and seafloor spreading Geomagnetic reversals are recorded in the
ocean crust In 1963 the discovery of magnetic stripes in the
ocean crust near ridge crests was tied to the concept of seafloor spreading
VL Geodynamik & Tektonik, WS 0809
Paleomagnetic reversals recorded by Paleomagnetic reversals recorded by basalt at mid-ocean ridgesbasalt at mid-ocean ridges
VL Geodynamik & Tektonik, WS 0809
Inpretation of magnetic anomalies from ship-track wiggles, (Barckhausen et al. 2001).
VL Geodynamik & Tektonik, WS 0809
Testing the plate tectonics modelTesting the plate tectonics model
Magnetic reversals and seafloor spreading Paleomagnetism (evidence of past magnetism
recorded in the rocks) was the most convincing evidence set forth to support the concept of seafloor spreading
The Pacific has a faster spreading rate than the Atlantic
VL Geodynamik & Tektonik, WS 0809
Testing the plate tectonics modelTesting the plate tectonics model
Plate tectonics and earthquakes Plate tectonics model accounts for the global
distribution of earthquakes – Absence of deep-focus earthquakes along the
oceanic ridge is consistent with plate tectonics theory – Deep-focus earthquakes are closely associated with
subduction zones – The pattern of earthquakes along a trench provides a
method for tracking the plate's descent
VL Geodynamik & Tektonik, WS 0809
Deep-focus earthquakes occur along Deep-focus earthquakes occur along convergent boundariesconvergent boundaries
VL Geodynamik & Tektonik, WS 0809
Earthquake foci in the vicinity Earthquake foci in the vicinity of the Japan trenchof the Japan trench
VL Geodynamik & Tektonik, WS 0809
Testing the plate tectonics modelTesting the plate tectonics model
Evidence from ocean drillingSome of the most convincing evidence
confirming seafloor spreading has come from drilling directly into ocean-floor sediment
– Age of deepest sediments – Thickness of ocean-floor sediments verifies
seafloor spreading
VL Geodynamik & Tektonik, WS 0809
Testing the plate tectonics modelTesting the plate tectonics model
Hot spots Caused by rising plumes of mantle
material Volcanoes can form over them
(Hawaiian Island chain)Most mantle plumes are long-lived
structures and at least some originate at great depth, perhaps at the mantle-core boundary
VL Geodynamik & Tektonik, WS 0809
The Hawaiian Islands have formed The Hawaiian Islands have formed over a stationary hot spotover a stationary hot spot
VL Geodynamik & Tektonik, WS 0809
Measuring plate motionsMeasuring plate motions
A number of methods have been em-ployed to establish the direction and rate of plate motion
Volcanic chains Paleomagnetism Very Long Baseline Interferometry (VLBI) Global Positioning System (GPS)
VL Geodynamik & Tektonik, WS 0809
Measuring plate motionsMeasuring plate motions
Calculations show that Hawaii is moving in a northwesterly
direction and approaching Japan at 8.3 centimeters per year
A site located in Maryland is retreating from one in England at a rate of about 1.7 centimeters per year
VL Geodynamik & Tektonik, WS 0809
The driving mechanismThe driving mechanism
No one driving mechanism accounts for all major facets of plate tectonics
Several mechanisms generate forces that contribute to plate motion
Ridge push Slab pull
Models– Layering at 660 kilometers – Whole-mantle convection – Deep-layer model
VL Geodynamik & Tektonik, WS 0809
DeformationDeformation
Deformation is a general term that refers to all changes in the original form and/or size of a rock body
Most crustal deformation occurs along plate margins
How rocks deformRocks subjected to stresses greater
than their own strength begin to deform usually by folding, flowing, or fracturing
VL Geodynamik & Tektonik, WS 0809
FaultsFaults
Faults are fractures in rocks along which appreciable displacement has taken place
Sudden movements along faults are the cause of most earthquakes
Classified by their relative movement which can be
Horizontal, vertical, or oblique
VL Geodynamik & Tektonik, WS 0809
FaultsFaults
Types of faultsDip-slip faults
– Movement is mainly parallel to the dip of the fault surface
– May produce long, low cliffs called fault scarps
– Parts of a dip-slip fault include the hanging wall (rock surface above the fault) and the footwall (rock surface below the fault)
VL Geodynamik & Tektonik, WS 0809
Concept of hanging wall and footwall Concept of hanging wall and footwall along a faultalong a fault
VL Geodynamik & Tektonik, WS 0809
FaultsFaults
Types of dip-slip faults– Normal fault
• Hanging wall block moves down relative to the footwall block
• Accommodate lengthening or extension of the crust
• Most are small with displacements of a meter or so
• Larger scale normal faults are associated with structures called fault-block mountains
VL Geodynamik & Tektonik, WS 0809
A normal fault A normal fault
VL Geodynamik & Tektonik, WS 0809
FaultsFaults
Types of dip-slip faults– Reverse and thrust faults
• Hanging wall block moves up relative to the footwall block
• Reverse faults have dips greater than 45o and thrust faults have dips less then 45o
• Accommodate shortening of the crust• Strong compressional forces
VL Geodynamik & Tektonik, WS 0809
A reverse faultA reverse fault
VL Geodynamik & Tektonik, WS 0809
A thrust fault A thrust fault
VL Geodynamik & Tektonik, WS 0809
FaultsFaults
Strike-slip fault Dominant displacement is horizontal and
parallel to the strike of the fault Types of strike-slip faults
– Right-lateral – as you face the fault, the block on the opposite side of the fault moves to the right
– Left-lateral – as you face the fault, the block on the opposite side of the fault moves to the left
VL Geodynamik & Tektonik, WS 0809
A strike-slip faultA strike-slip fault
VL Geodynamik & Tektonik, WS 0809
FaultFault
Strike-slip faultTransform fault
– Large strike-slip fault that cuts through the lithosphere
– Accommodates motion between two large crustal plates
VL Geodynamik & Tektonik, WS 0809
The San Andreas fault system The San Andreas fault system is a major transform faultis a major transform fault
VL Geodynamik & Tektonik, WS 0809
Mountain beltsMountain belts
Orogenesis – the processes that col-lectively produce a mountain belt
Includes folding, thrust faulting, meta-morphism, and igneous activity
Mountain building has occurred during the recent geologic past
Alpine-Himalayan chain American Cordillera Mountainous terrains of the western
Pacific
VL Geodynamik & Tektonik, WS 0809
Earth’s major mountain beltsEarth’s major mountain belts
VL Geodynamik & Tektonik, WS 0809
Mountain beltsMountain belts
Older Paleozoic- and Precambrian-age mountains
Appalachians Urals in Russia
Several hypotheses have been proposed for the formations of Earth’s mountain belts
VL Geodynamik & Tektonik, WS 0809
Mountain building at Mountain building at convergent boundariesconvergent boundaries
Plate tectonics provides a model for orogenesis Mountain building occurs at convergent plate boundaries Of particular interest are active subduction zones
– Volcanic arcs are typified by the Aleutian Islands and the Andean arc of western South America
VL Geodynamik & Tektonik, WS 0809
Mountain building at Mountain building at convergent boundariesconvergent boundaries
Aleutian-type mountain building Where two ocean plates converge and one is subducted
beneath the other Volcanic island arcs result from the steady subduction of
oceanic lithosphere – Most are found in the Pacific – Active island arcs include the Mariana, New Hebrides,
Tonga, and Aleutian arcs
VL Geodynamik & Tektonik, WS 0809
Mountain building at Mountain building at convergent boundariesconvergent boundaries
Aleutian-type mountain building Volcanic island arcs
– Continued development can result in the formation of mountainous topography consisting of igneous and metamorphic rocks
VL Geodynamik & Tektonik, WS 0809
Formation of a volcanic island arcFormation of a volcanic island arc
VL Geodynamik & Tektonik, WS 0809
Mountain building at Mountain building at convergent boundariesconvergent boundaries
Andean-type mountain building Mountain building along continental margins
– Involves the convergence of an oceanic plate and a plate whose leading edge contains continental crust
– Exemplified by the Andes Mountains
VL Geodynamik & Tektonik, WS 0809
Mountain building at Mountain building at convergent boundariesconvergent boundaries
Andean-type mountain building Stages of development - passive margin
– First stage– Continental margin is part of the same plate as the
adjoining oceanic crust – Deposition of sediment on the continental shelf is
producing a thick wedge of shallow-water sediments– Turbidity currents are depositing sediment on the
continental rise and slope
VL Geodynamik & Tektonik, WS 0809
Mountain building at Mountain building at convergent boundariesconvergent boundaries
Andean-type mountain building Stages of development – active continental margins
– Subduction zone forms – Deformation process begins – Convergence of the continental block and the subducting
oceanic plate leads to deformation and metamorphism of the continental margin
– Continental volcanic arc develops
VL Geodynamik & Tektonik, WS 0809
Mountain building at Mountain building at convergent boundariesconvergent boundaries
Andean-type mountain building Composed of roughly two parallel zones
– Accretionary wedge
• Seaward segment
• Consists of folded, faulted, and meta-morphosed sediments and volcanic debris
VL Geodynamik & Tektonik, WS 0809
Orogenesis along an Andean-type Orogenesis along an Andean-type subduction zonesubduction zone
VL Geodynamik & Tektonik, WS 0809
Orogenesis along an Andean-type Orogenesis along an Andean-type subduction zonesubduction zone
VL Geodynamik & Tektonik, WS 0809
Orogenesis along an Andean-type Orogenesis along an Andean-type subduction zonesubduction zone
VL Geodynamik & Tektonik, WS 0809
Mountain building at Mountain building at convergent boundariesconvergent boundaries
Continental collisions Two lithospheric plates, both carrying continental crust The Himalayan Mountains are a youthful mountain range
formed from the collision of India with the Eurasian plate about 45 million years ago
VL Geodynamik & Tektonik, WS 0809
Mountain building at Mountain building at convergent boundariesconvergent boundaries
Continental collisions The Himalayan Mountains
– Spreading center that propelled India northward is still active
– Similar but older collision occurred when the European continent collided with the Asian continent to produce the Ural mountains
VL Geodynamik & Tektonik, WS 0809
Plate relationships prior to the Plate relationships prior to the collision of India with Eurasiacollision of India with Eurasia
VL Geodynamik & Tektonik, WS 0809
Position of India in relation to Eurasia Position of India in relation to Eurasia at various timesat various times
VL Geodynamik & Tektonik, WS 0809
Formation of the HimalayasFormation of the Himalayas
VL Geodynamik & Tektonik, WS 0809
Mountain building at Mountain building at convergent boundariesconvergent boundaries
Continental accretion and mountain building A third mechanism of orogenesis Small crustal fragments collide and merge with
continental margins Responsible for many of the mountainous regions
rimming the Pacific Accreted crustal blocks are called terranes
VL Geodynamik & Tektonik, WS 0809
Mountain building at Mountain building at convergent boundariesconvergent boundaries
Continental accretion and mountain building Terranes consist of any crustal fragments whose
geologic history is distinct from that of the adjoining terranes
As oceanic plates move, they carry embedded oceanic plateaus, volcanic island arcs and microcontinents to an Andean-type subduction zone
VL Geodynamik & Tektonik, WS 0809
Vertical movements of the crustVertical movements of the crust
In addition to the horizontal movements of lithospheric plates, vertical movement also occurs along plate margins as well as the interiors of continents far from plate boundaries
VL Geodynamik & Tektonik, WS 0809
Vertical movements of the crustVertical movements of the crust
Isostatic adjustment Less dense crust floats on top of the denser
and deformable rocks of the mantle Concept of floating crust in gravitational
balance is called isostasy If weight is added or removed from the crust,
isostatic adjustment will take place as the crust subsides or rebounds
VL Geodynamik & Tektonik, WS 0809
Der Wilson-ZyklusDer Wilson-Zyklus
Ein Wilson-Zyklus beschreibt die Entstehung, die Entwicklung und das Verschwinden eines Ozeans.
Ein Wilson-Zyklus beschreibt die Entstehung, die Entwicklung und das Verschwinden eines Ozeans.
Die einzelnen Stadien sind: Zerbrechen kontinentaler Kruste, Entstehung einer ozeanischen Spreizungszone, maximale Ausdehnung der Ozeanischen Kruste, Subduktion, Verschwinden der ozeanischenKruste, Kontinent – Kontinent - Kollision
Die einzelnen Stadien sind: Zerbrechen kontinentaler Kruste, Entstehung einer ozeanischen Spreizungszone, maximale Ausdehnung der Ozeanischen Kruste, Subduktion, Verschwinden der ozeanischenKruste, Kontinent – Kontinent - Kollision
VL Geodynamik & Tektonik, WS 0809
Die Stadien eines Wilson-ZyklusDie Stadien eines Wilson-ZyklusAn verschieden weit entwickelter ozeanischer Kruste kann man
einzelne Stadien eines Wilson-Zyklus beobachten:
Bildung eines kontinentalen Grabens (Ostafrikanischer Graben)Bildung eines kontinentalen Grabens (Ostafrikanischer Graben)
Beginnende Ozeanisierung (Rotes Meer) Beginnende Ozeanisierung (Rotes Meer)
Maximale Ausdehnung der ozeanischen Kruste mit passiven Kontinentalrändern (Atlantik)
Maximale Ausdehnung der ozeanischen Kruste mit passiven Kontinentalrändern (Atlantik)
Subduktion der ozeanischen Kruste mit aktiven Kontinental- rändern (Pazifik)
Subduktion der ozeanischen Kruste mit aktiven Kontinental- rändern (Pazifik)
Restozean (Mittelmeer)Restozean (Mittelmeer)
Kontinent – Kontinent – Kollision (Himalaya)Kontinent – Kontinent – Kollision (Himalaya)
VL Geodynamik & Tektonik, WS 0809
1.) Grabenbildung (Rifting)1.) Grabenbildung (Rifting) Beginnt mit einem Tripelpunkt auf kontinentaler Kruste
Süd-Amerika Afrika
Äquator
Kreide
Äquator
Rezent
Tripelpunkt
Benue-Trog(Aulakogen)
Rotes Meer
Afar-Senke
Golf von Aden
VL Geodynamik & Tektonik, WS 0809
Entwicklung eines kontinentalen Entwicklung eines kontinentalen GrabensGrabens
aufdringendes basaltisches Magma
LavadeckenTuffe, vulkanischer Schutt
terrestrische Sedimente
Evaporite (Salze)
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Der Rhein Rhône-GrabenDer Rhein Rhône-Graben
Tiefe der Kruste-Mantel-Grenze
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Profil durch den RheingrabenProfil durch den Rheingraben
Asthenolith(Mantelkissen,Manteldiapir)
Oberer MantelKontinentaleKruste
VL Geodynamik & Tektonik, WS 0809
Der Ostafrikanische GrabenDer Ostafrikanische Graben
Nairobi
WesternRift
GregoryRift
W E
Länge 4 000 kmBreite 30 – 70 kmVersatz > 6 000 m
Länge 4 000 kmBreite 30 – 70 kmVersatz > 6 000 m
VL Geodynamik & Tektonik, WS 0809
Merkmale von kontinentalen GräbenMerkmale von kontinentalen Gräben
Hohe SeismizitätHohe Seismizität
Hoher Wärmefluß (> 2.0 HFU)Hoher Wärmefluß (> 2.0 HFU)
Alkaliner Magmatismus undVulkanismusAlkaliner Magmatismus undVulkanismus
Negative Schwere-Anomalie(Bouguer-Schwere)Negative Schwere-Anomalie(Bouguer-Schwere)
VL Geodynamik & Tektonik, WS 0809
Schwere-AnomalieSchwere-Anomalie
Gemessen wird die Erdbeschleunigung in gal1 gal = 1 cm/sec2 = 1000 mgal.
normal: 980 gal
Gemessen wird die Erdbeschleunigung in gal1 gal = 1 cm/sec2 = 1000 mgal.
normal: 980 gal
~7.0>8.0 >8.0
+ +-Bouguer- Schwere
hochliegendeMoho
leichteSedimente
VL Geodynamik & Tektonik, WS 0809
Bildung eines Bildung eines mittelozeanischenmittelozeanischen
RückensRückens
Bildung eines Bildung eines mittelozeanischenmittelozeanischen
RückensRückens
2.) Stadium2.) Stadium
VL Geodynamik & Tektonik, WS 0809
Entstehung neuer ozeanischer KrusteEntstehung neuer ozeanischer Kruste
Beispiel: Rotes Meer, Golf von Aden,Afar- (Danakil-) Senke
Beispiel: Rotes Meer, Golf von Aden,Afar- (Danakil-) Senke
Rotes MeerRotes Meer
Golf von AdenGolf von Aden
Afar - DreieckAfar - Dreieck
VL Geodynamik & Tektonik, WS 0809
Unterschiede zu GräbenUnterschiede zu Gräben
Entstehung ozeanischer KrusteEntstehung ozeanischer Kruste
Positive Bouguer-AnomaliePositive Bouguer-Anomalie
VL Geodynamik & Tektonik, WS 0809
Ausbreitung ozeanischer Ausbreitung ozeanischer LithosphäreLithosphäre
Ausbreitung ozeanischer Ausbreitung ozeanischer LithosphäreLithosphäre
3. Stadium3. Stadium
VL Geodynamik & Tektonik, WS 0809
Maximale Öffnung eines OzeansMaximale Öffnung eines Ozeans
nach Press & Siever (Spektrum Lehrbuch), 1995
Beispiel Atlantik
passiveKontinentalränder
Tiefseebecken
VL Geodynamik & Tektonik, WS 0809
Profil durch den AtlantikProfil durch den Atlantik
Kontinental-rand
Kontinental-randTiefsee-
BeckenTiefsee-Becken
MittelozeanischerRücken
2000m4000m
Kontinental-rand
Kontinental-randTiefsee-
BeckenTiefsee-Becken
MittelozeanischerRücken
2000m4000m
Schematisches Profil durch den Nordatlantik
VL Geodynamik & Tektonik, WS 0809
Stadium 4Stadium 4Subduktion ozeanischer Subduktion ozeanischer
KrusteKruste(rezentes Beispiel: Pazifik)(rezentes Beispiel: Pazifik)
VL Geodynamik & Tektonik, WS 0809
SubduktionSubduktion3. Magmatischer Bogen
3. Magmatischer Bogen
4. Seismizität an der Wadati- Benioff-Zone
4. Seismizität an der Wadati- Benioff-Zone
Hochdruck-Niedrig-temperatur-Metam.
Hochdruck-Niedrig-temperatur-Metam.
Hochtemperatur-Niedrigdruck-Metam.
Hochtemperatur-Niedrigdruck-Metam.
5. paarige meta- morphe Gürtel
5. paarige meta- morphe Gürtel
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paarige metamorphe Gürtel in Japanpaarige metamorphe Gürtel in Japan
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Fossile Subduktionszonen:Fossile Subduktionszonen:
Eine ehemalige Subduktionszone erkennt man am Vorhandensein von:
Ophiolithen(Ophiolithische Sutur)
Ophiolithen(Ophiolithische Sutur)
magmatischen Gesteinenmagmatischen Gesteinen
Hochdruck-Gesteinen (Blauschiefer)Hochdruck-Gesteinen (Blauschiefer)
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steilerEintauch-winkel
Bildung von RandbeckenBildung von Randbecken
Flacher EintauchwinkelHigh StressSubduktionHigh StressSubduktion
Low StressSubduktionLow StressSubduktion
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Stadium 5Stadium 5RestmeerRestmeer
(Beispiel: Mittelmeer) (Beispiel: Mittelmeer)
Stadium 5Stadium 5RestmeerRestmeer
(Beispiel: Mittelmeer) (Beispiel: Mittelmeer)
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Das Mittelmeer und Schwarze Meer Das Mittelmeer und Schwarze Meer als Restmeereals Restmeere
Aus Press & Siever, 1995 (Spektrum Lehrbücher)
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Terrankarte des MittelmeersTerrankarte des Mittelmeers
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Stadium 6Stadium 6Kontinent-Kontinent-KollisionKontinent-Kontinent-Kollision
Stadium 6Stadium 6Kontinent-Kontinent-KollisionKontinent-Kontinent-Kollision
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Kontinent-Kontinent-KollisionKontinent-Kontinent-Kollision
Asthenosphäre
Litho-sphäre
Vorland-becken
Zentral-gürtel
Akkretions-keil
Geo
sutu
r
Hinterland
Regionale Metamorphoseund Anatexis Mantel-
delamination
Umgezeichnet nach Eisbacher, 1991
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Kontinent-Kontinent-KollisionKontinent-Kontinent-Kollision
kontinentaleKruste
kontinentaleKruste
kontinentaleKruste
kontinentaleKruste
Slab-breakoff
Slab-breakoff
Über-schiebungen
Über-schiebungen
Sutur-zone
Sutur-zone
OphiolitheOphiolithe
MélangeMélange
Umgezeichnet nach Press & Siever, 1995 (Spektrum)
UnderplatingUnderplating
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Kollision Indiens mit EurasienKollision Indiens mit Eurasien
Krustenver-kürzunginsgesamt2000 kmin 40 Ma
Krustenver-kürzunginsgesamt2000 kmin 40 Ma
Aus Press & Siever, 1995 (Spektrum Lehrbücher)
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Entstehung des HimalayaEntstehung des Himalaya
University of Western Australia
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Tektonik im Himalaya-HinterlandTektonik im Himalaya-Hinterland
Konvergenz
Dehnung
Escape-Tektonik
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ZusammenfassungZusammenfassung
Die Plattentektonik ist der an der Erdoberfläche auftretende Ausdruck der Mantelkonvektion im Erdinneren. Sie
beschreibt die Bewegungen der Lithosphärenplatten und die daraus resultierenden geologischen Prozesse.
Zu diesen zählen u.a. die Entstehung von Faltengebirgen („Orogenese“), von mittelozeansichen Rücken und von
Transformstörungen.
Die großräumigen Deformationen der Lithosphäre sind wiederum die Ursache von zahlreichen geophysikalischen
Phänomenen, wie z.B. Vulkanismus oder Seismizität.