Transcript PLATE TECTONICS - uni

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
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;
Earth’s 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.
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.
Evidences for Continental Drift
• The shape of the continent seems to
fit together.
Evidences for Continental Drift
• The shape of the continent seems to
fit together.
• Matching Geological Units
Evidences for Continental Drift
• The shape of the continent seems to
fit together.
• Matching Geological Units
• Distribution of Fossils
Evidences for Continental Drift
• The shape of the continent seems to
fit together.
• Matching Geological Units
• Distribution of Fossils
• Distribution of Climatic Belts
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.
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???
APW
Apparent Polar Wander
A tape recorder
“An essay of GeoPoetry”
Magnetic Reversal on Sea Floor
Plate Margins on a flat planet
Transform LL
Constructive
Convergent
Transform RL
Plate Margins on a flat planet
Transform LL
Constructive
Convergent
Transform RL
http://www.gasd.k12.pa.us/~dpompa/Mini%20Lecture.html
From Lowrie, 2007
From Lowrie, 2007
How fast plates move ???
Hot spot
www.tulane.edu/.../geol204/volclandforms.htm
www.gasd.k12.pa.us/~dpompa/Mini%20Lecture.html
www.geophysik.uni-frankfurt.de/~schmelin/
Hot spot
www.tulane.edu/.../geol204/volclandforms.htm
www.gasd.k12.pa.us/~dpompa/Mini%20Lecture.html
www.geophysik.uni-frankfurt.de/~schmelin/