Transcript The Earth`s Interior & Plate Tectonics

The Earth’s Interior
& Plate Tectonics
Physical Science Chapter 17 Section 1
The Earth’s Interior
The Earth’s Interior can be broken up into 4
major zones
Crust
Mantle
Outer core
Inner core
Surrounding
the interior
is the
Atmosphere
The Crust
The crust is very thin (average 20 km) & Brokenup into plates.
This does not sound very thin but if you were to
imagine the Earth as a football, the crust would
be about ½millimeter thick.
The thinnest parts are under the oceans (Oceanic
Crust) and go to a depth of roughly 10
kilometers. It is more dense than under
continents.
The thickest parts are the continents (Continental
Crust) which extend down to 35 kilometers on
average. The continental crust in the Himalayas is
some 75 kilometres deep.
The Mantle
A rocky layer
located below the
crust with a
thickness of 2885
kilometers
The upper part of
the mantle together
with the crust is
called the
Lithosphere.
The Mantle (cont…)
The mantle extends about half way to the
centre. It's made of solid rock and
behaves like an extremely viscous liquid (This is the tricky bit... the mantle is a
solid which flows) The convection of heat
from the centre of the Earth is what
ultimately drives the movement of the
tectonic plates and cause mountains to
rise.
The Outer Core
A layer about
2270 kilometers
thick, which is
made of molten
(liquid) iron &
nickel.
The movement
of this liquid
core is
responsible for
the Earth's
magnetic field
The Inner Core
The bit in the middle!
It is made of solid
iron and nickel with a
radius of about 1216
km.
Temperatures in the
core are thought to
be in the region of
5000-6000°c and it's
solid due to the
massive pressure.
The Theory of Plate Tectonics
States that Earth's rigid outer shell, called
the lithosphere, consists of seven large and
numerous smaller segments called plates
that are in motion relative to each other.
Origins
Alfred Wegner
proposed
Continental Drift
when he noticed
that the continents
fit together like
jigsaw pieces.
Later, with more
evidence, this
became the theory
of Plate Tectonics
Evidence for Plate Tectonics
The evidence Wegner
used for his original
theory
Continents fit
together
Matching Rocks &
Fossils
Paleomagnetism: Study
of the changes in
Earth’s Magnetic Field
Evidence for the theory (cont…)
The edges of these
plates (called Plate
Boundaries), where
they move against
each other, are sites
of intense geologic
activity, such as
earthquakes,
volcanoes, and
mountain building.
Types of Plate Boundaries
A. Divergent plate
boundaries
B. Convergent
plate boundaries
C. Transform fault
boundaries
Divergent Plate Boundaries
(constructive margins)
Two plates move
apart
Mantle material
upwells to create
new seafloor
Continental rifts
form at spreading
centers within a
continent
Divergent Plate Boundaries (cont…)
Convergent plate boundaries
(destructive margins)
Plates collide, an
ocean trench forms
and lithosphere is
subducted into the
mantle
There are three
types of Convergent
Plate Boundary
Oceanic-continental convergence
Denser oceanic slab
sinks into the
asthenosphere
Pockets of magma
develop and rise
Continental volcanic
arcs form
e.g., Andes Mountain
Range
e.g., Cascades Mountain
Range
Oceanic-oceanic convergence
Two oceanic slabs
converge and one
descends beneath the
other
Often forms volcanoes
on the ocean floor
Volcanic island arcs
forms as volcanoes
emerge from the sea
e.g., Aleutian islands
e.g., Mariana islands
Continental-continental convergence
When subducting plates contain continental
material, two continents collide
Can produce new mountain ranges such as
the Himalayas
Example of a continental-continental
Subduction
Transform Fault boundaries
Plates slide past one
another
No new crust is
created
No crust is
destroyed