Introduction to Earth System

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Introduction to Earth System

• Solid Earth part
• Rocco Malservisi
• roccom_at_lmu.de
• Phone [phone]

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Magnetic Field is a vector
It has an intensity (can be measured looking At
the oscillation of a compass) And a direction The
direction change with the position
Magnetic Pole The place where the compass is
pointing Down Magnetic Equator The place where
the compass is horizontal
The Magnetic Poles are close to the
geographical Poles but do not coincide (11 off)
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The Earths Magnetic Field
B (X, Y, Z) Or B (F, I, D ) OrB
(D, H, Z)
F intensity I inclination D declination H
Horizontal component
The seven elements of the (local) magnetic
fieldin the geographic coordinate system
I. Geomagnetic field Local Geomagnetic
Field Vector
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The place where the axis of the dipole intersect
the surface Of the earth are called geomagnetic
poles
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other secular variation reversal
From Butler, Palaeomagnetism, 1992.
Slide I. Geomagnetic field Temporal
Variations
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PaleoMagnetic FieldMagnetization of Rocks
DRM Detrital Remanent Magnetization
TRM Thermal Remanent Magnetization
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Gesteinsmagnetisierung Curie Temperatur etwa
580 Grad C für Magnetit
680 Grad C für Hämatit Blocking
Temperatur Typische Schmelztemperaturen liegen
allerdings bei 1100 800 Grad C, also
wesentlich höher. Das heißt, Gesteine können
eine Magnetisierung im Umfeld annehmen, und
diese bei Abkühlung unter die Blocking-Temperatur
auf geologische Zeiträume hinweg behalten.
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Wir unterscheiden Thermoremanente
Magnetisierung TRM Depositionale Magnetisierung
(in Sedimenten) DRM Chemoremanente
Magnetisierung CRM DRM entsteht durch die
geordnete Ablagerung magnetischer Minerale in
Sedimentgesteinen zur Zeit der Deposition. CRM
entsteht durch das langsame Mineralwachstum nach
der Ablagerung oder Erstarrung.
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A tape recorder An essay of GeoPoetry
Submarine Lava flow at ridge From
www.ridge2000.org/science/tcs/epr06activity.php
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Dating the Magnetic Reversal
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PaleoPole position
If we measure I we can compute The original
Latitude, from this If we know the position of
the Sample we compute the Position of the
paleopole. Note if the plate move we have an
Apparent Polar Wander
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Geomagnetic inclination (IGRF)
I. Geomagnetic field Worldwide Variation of
I
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Hierbei ist ? die sogenannte magnetische
Co-Latitude.
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Beispiel-Rechnung Basalt-Probe aus einem
gegenwärtigen Ort an 47 S, 20 E. Die remanente
Magnetisierung ergibt eine Paleo-Inklination von
30 Grad. Paleo-Deklination N30E. Bestimmen wir
die Paläolatitude
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Position 47S 20E
StereoNet
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Position 47S 20E Declination N30E
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Position 47S 20E Declination N30E Inclination
30 grad Paleolat16 grad Distance Pole74 grad
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Position 47S 20E Declination N30E Inclination
30 grad Paleolat16 grad Distance Pole74 grad
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APW Apparent Polar Wander
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Since the mechanism of generation of the magnetic
field is influenced by the rotation the dipole is
mainly oriented along the rotation axis and
people use the magnetic pole as past proxy for
the rotation axis
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APW Apparent Polar Wander
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Ocean Spreading
Looking for subs the British and Americans
developed a map of Magnetic anomalies of the sea
floor, in 1961 Harry Hess explained It using
seafloor spreading theory.
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A tape recorder An essay of GeoPoetry
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A tape recorder An essay of GeoPoetry
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Dating the Magnetic Reversal
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Chron
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A tape recorder An essay of GeoPoetry
Isochron (or chron)
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Continental Drift
In 1912 Wegener suggested that the current
position of the continents has evolved and that
the continents were once fit together in a
supercontinent called PANGAEA.
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Evidences for Continental Drift

• The shape of the continent seems to fit
  together.

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Evidences for Continental Drift

• The shape of the continent seems to fit
  together.
• Matching Geological Units

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Evidences for Continental Drift

• The shape of the continent seems to fit
  together.
• Matching Geological Units
• Distribution of Fossils

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Evidences for Continental Drift

• The shape of the continent seems to fit
  together.
• Matching Geological Units
• Distribution of Fossils
• Distribution of Climatic Belts

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Evidences for Continental Drift

• The shape of the continent seems to fit
  together.
• Matching Geological Units
• Distribution of Fossils
• Distribution of Climatic Belts
• Location of past glacial regions.

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Evidences for Continental Drift

• The shape of the continent seems to fit
  together.
• Matching Geological Units
• Distribution of Fossils
• Distribution of Climatic Belts
• Location of past glacial regions.

BIG PROBLEM!!!! HOW CAN THE WEAK CONTINENTS MOVE
TROUGH THE STRONG OCEANS?? WHERE THE FORCES TO
MOVE THE CONTINENTS COME FROM???
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APW Apparent Polar Wander
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Since the mechanism of generation of the magnetic
field is influenced by the rotation the dipole is
mainly oriented along the rotation axis and
people use the magnetic pole as past proxy for
the rotation axis
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A tape recorder An essay of GeoPoetry
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Magnetic Reversal on Sea Floor
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PLATE TECTONICS
Plate Tectonic is a theory that unify different
previous geological theories (CONTINENTAL DRIFT
and OCEAN SPREADING) and that can explain the
majority of the solid earth system
observations. Basic concept The outermost
layer (LITHOSPHERE) is divided in a small number
of rigid plates in relative motion one respect
to the other and that are moving on a weak
ASTHENOSPHERE
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PLATE TECTONICS

• Basic concept
• The outermost layer (LITHOSPHERE) is divided in a
  small number of rigid plates in relative motion
  one respect to the other and that are moving on a
  weak ASTHENOSPHERE
• Basic Assumptions
• The astenosphere viscosity is low enough to allow
  on long time scale for viscous flow
• The generation of new plate material occurs by
  sea floor spreading
• The new oceanic lithosphere form part of a rigid
  plate that may or may not include continental
  material
• Earths surface area remains constant this means
  that seafloor spreading must be balanced by
  consumption of plate elsewhere
• Lithospheric plate are capable of transmitting
  stress over great horizontal scale. In other
  words plates are rigid and the deformation is
  concentrated along the boundaries.

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Brittle Ductile behavior
brittle ductile
The behavior is dependent on the temperature, the
material But also by the RATE!!!!