Download What are the causes of plate motion and what

WHAT ARE THE CAUSES OF PLATE
MOTION AND WHAT FEATURES DO
THEY FORM?
Plate tectonics is a scientific theory that describes the
large-scale motions of Earth's lithosphere. The model
builds on the concepts of continental drift, developed
during the first few decades of the 20th century. The
geoscientific community accepted the theory after the
concepts of seafloor spreading were developed in the
late 1950s and early 1960s.
WHAT ARE THE CAUSES OF PLATE
MOTION AND WHAT FEATURES DO
THEY FORM?
On Earth, there are seven or eight major plates (depending on how they
are defined) and many minor plates.
WHAT ARE THE CAUSES OF PLATE
MOTION AND WHAT FEATURES DO
THEY FORM?
• Different types of crusts
(plates):
• Oceanic crust: the part of
Earth's lithosphere that surfaces
in the ocean basins. Oceanic
crust is primarily composed
of mafic rocks, which is rich in
iron and magnesium. It is
thinner than continental crust
but more dense at
2.9 grams/cm3.
WHAT ARE THE CAUSES OF PLATE
MOTION AND WHAT FEATURES DO
THEY FORM?
• Different types of crusts (plates):
• Continental crust is the layer of
igneous, sedimentary, and
metamorphic rocks which forms
the continents and the areas of
shallow seabed close to their
shores, known as continental
shelves. Consisting mostly of
granitic rock, continental crust has
a density of about 2.7 g/cm3 and
is less dense than the material of
the Earth's mantle (density of
about 3.3 g/cm3) and less dense
than oceanic crust.
GREAT, SO HOW DO THEY
MOVE?
WHAT ARE THE CAUSES OF PLATE
MOTION AND WHAT FEATURES DO
THEY FORM?
• Currently, the most accepted explanation for
plate movement is the convection currents that
are going on in the Earth’s mantle.
WHAT ARE THE CAUSES OF PLATE
MOTION AND WHAT FEATURES DO
THEY FORM?
Ridge push or sliding
plate force is a proposed
mechanism for plate
motion in plate tectonics.
Because mid-ocean
ridges lie at a higher
elevation than the rest of
the ocean floor, gravity
causes the ridge to push
on the lithosphere that
lies farther from the ridge.
WHAT ARE THE CAUSES OF PLATE
MOTION AND WHAT FEATURES DO
THEY FORM?
• Example: Mid Ocean Ridge
WHAT ARE THE CAUSES OF PLATE
MOTION AND WHAT FEATURES DO
THEY FORM?
Slab pull is the movement
of tectonic plate
lithosphere due to
convection currents in
the asthenosphere (midmantle). When the
currents circulate they
pull the tectonic plates
down causing
subduction. The slab pull
force is a tectonic plate
force due to subduction.
WHAT ARE THE CAUSES OF PLATE
MOTION AND WHAT FEATURES DO
THEY FORM?
• Convection:
The transfer of
heat by the
actual
movement of
the warmed
matter.
Convection is
the transfer of
heat energy in
a gas or liquid
by movement
of currents.
Conduction: The transfer of energy through
matter from particle to particle.
Radiation: Electromagnetic waves that directly
transport ENERGY through space
WHAT ARE THE CAUSES OF PLATE
MOTION AND WHAT FEATURES DO
THEY FORM?
How do plates interact with each other and what do
the interactions cause?
• Boundaries
• Divergent
• Convergent
• Transform
• Faults
• Normal
• Reverse/Thrust
• Strike-slip
WHAT ARE THE CAUSES OF PLATE
MOTION AND WHAT FEATURES DO
THEY FORM?
• Divergent plate boundaries are a linear feature that
exists between two tectonic plates that are moving
away from each other
WHAT ARE THE CAUSES OF PLATE
MOTION AND WHAT FEATURES DO
THEY FORM?
Examples: mid-ocean ridges and rift valleys
WHAT ARE THE CAUSES OF PLATE
MOTION AND WHAT FEATURES DO
THEY FORM?
• A convergent plate
boundary is an actively
deforming region where
two (or more) tectonic
plates or fragments of
lithosphere move toward
one another and collide.
As a result of pressure,
friction, and plate
material melting in the
mantle, earthquakes and
volcanoes are common
near convergent
boundaries.
WHAT ARE THE CAUSES OF PLATE
MOTION AND WHAT FEATURES DO
THEY FORM?
Examples:
• Trenches
• Mountain ranges
• Volcanoes
WHAT ARE THE CAUSES OF PLATE
MOTION AND WHAT FEATURES DO
THEY FORM?
Faults are a planar fracture
or discontinuity in a volume
of rock, across which there
has been significant
displacement along the
fractures as a result of earth
movement. They result from
types of stress which in turn
cause strain that could then
produce an earthquake.
WHAT ARE THE CAUSES OF PLATE
MOTION AND WHAT FEATURES DO
THEY FORM?
In a normal fault, the block above the fault moves
down relative to the block below the fault. This fault
motion is caused by tensional forces and results in
extension.
Examples: Sierra Nevada/Owens Valley; Basin &
Range faults
WHAT ARE THE CAUSES OF PLATE
MOTION AND WHAT FEATURES DO
THEY FORM?
WHAT ARE THE CAUSES OF PLATE
MOTION AND WHAT FEATURES DO
THEY FORM?
In a reverse fault, the block above the fault moves up
relative to the block below the fault. This fault motion
is caused by compressional forces and results in
shortening. A reverse fault is called a thrust fault if the
dip of the fault plane is small.
Examples: Rocky Mountains, Himalayas
WHAT ARE THE CAUSES OF PLATE
MOTION AND WHAT FEATURES DO
THEY FORM?
WHAT ARE THE CAUSES OF PLATE
MOTION AND WHAT FEATURES DO
THEY FORM?
In a strike-slip fault, the movement of blocks along a
fault is horizontal. The fault motion of a strike-slip fault
is caused by shearing forces.
Examples: San Andreas Fault, California; Anatolian
Fault, Turkey
WHAT ARE THE CAUSES OF PLATE
MOTION AND WHAT FEATURES DO
THEY FORM?