Introduction to Earth System

Introduction to Earth System
Solid Earth part
Rocco Malservisi
[email protected]
Phone: 2180 4201
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.
Example of
oceanic only
plate:
Pacific
Example of
Continental and
Oceanic Plate:
Africa
Plate Margins on a flat planet
Transform LL
Constructive
Convergent
Transform RL
http://www.gasd.k12.pa.us/~dpompa/Mini%20Lecture.html
How many plates???
How many plates???
Where do Eqs occur?
Earthquake are release of elastic
strain accumulated due to
deformation.
If plate are rigid must be at plate
boundaries!
In subduction zone the thermal
advection play a big role on
location of earthquakes.
Marshak, 2005
How many plates???
Seismicity from USGS Volcanoes from Smithsonian institute
How many plates???
How fast plates move ???
How fast plates move ???
How fast plates move ???
This is a picture of Shridhar Chillal from
India, who had grown his fingernails for
48 years. He wanted to be in the
Guinness Book of World Records, and
felt that this was his best chance. When
measured in 1998, they measured 20'2".
He now struggles with a permanently
disfigured hand, and nerve damage
resulting in deafness in his left ear.
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/
Plate Margins on a flat planet
Transform LL
Constructive
Convergent
Transform RL
Focal mechanisms
Focal mechanisms