Download PLATE TECTONICS

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/