Plate Tectonics
The Surface of
the Earth
Plate Tectonics
Theory and Pangaea
Earthquakes
Volcanoes
Mountains
The Surface of the Earth
The Earth has three layers; the crust, the
mantle, and the core. These three layers are
based on chemical composition.
The Surface of the Earth
The Earth has five layers
based on physical
properties. The layers
are the lithosphere, the
asthenosphere, the
mesosphere, the outer
core, and the inter core.
The Crust
• The crust is the top surface of the Earth. The
composition of the crust is mainly silicon,
oxygen, an aluminum.
• The crust is the layer above the mantle.
• The crust can be divided into two different
types; the continental crust and the oceanic
crust.
The Mantle
• The mantle is the middle layer of the Earth. It
is between the crust and the core.
• The mantle is dense and thick.
• The mantle is composed of mostly oxygen,
silicon, magnesium.
• The mantle is the largest portion of Earth. The
mantle is about 67% of the total mass of the
Earth.
The Core
• The core is in the center of the Earth. It is
below the mantle.
• The core is dense and metallic.
• The core is about 33% of the total mass of the
Earth.
The Lithosphere
• The lithosphere is the hard, cold, rigid part of
the crust and the upper portion of the mantle.
• The lithosphere is where the tectonic plates
are located.
The Asthenosphere
• The asthenosphere is below the lithosphere.
• Slow moving rocks are in this layer of the
Earth.
• Plate tectonics move on top of the
asthenosphere.
The Mesosphere
• The mesosphere is between the
asthenosphere and the outer core.
• The mesosphere is located in the lower
portion of the mantle.
• The rocks in the mesosphere flow even slower
here than they do in the asthenosphere.
The Outer Core
• The outer core is one part of the core of the
Earth.
• The outer core is liquid and is made up of iron
and nickel.
• The outer core is below the mesosphere and is
the top layer of the core.
The Inner Core
• The inner core is located in the center of the
Earth.
• The inner core is solid and is estimated to be
between 4,000°C and 5, 000°C.
• The inner core is about half the size of the
outer core.
Comparing the Chemical Composition of the
Earth to the Physical Properties of the Earth
Chemical Composition
Physical Properties
Crust (60 km)
Lithosphere (150 km)
Mantle (2,831 km)
Asthenosphere (260 km)
Mesosphere (2,481 km)
Core (3,480 km)
Outer Core (2,259 km)
Inner Core (1,221 km)
Comparing the Chemical Composition of the
Earth to the Physical Properties of the Earth
The Theory of Plate Tectonics
• Explains how the lithosphere moves on top of
the mesosphere.
• Explains tectonic plates are different sizes and
are not all shaped the same.
• Explains there are tectonic plates on both the
land and the ocean.
• Tectonic plates form along tectonic
boundaries.
Tectonic Boundaries
• Earthquakes, volcanoes, mountains, ocean
trenches, and mid-ocean ridges form along
tectonic boundaries.
• There are three types of tectonic boundaries.
– Convergent Boundaries
– Divergent Boundaries
– Transform Boundaries
Convergent Boundaries
• Occur were two lithosphere tectonic plates
collide.
• Can create mountains and mountain ranges
on land.
• Can cause volcanoes to form when the denser
oceanic crust sinks below the less denser
continental crust. This is called subduction.
Divergent Boundaries
• Divergent boundaries separate or pull apart at
tectonic plates.
• Most divergent boundaries are located on the
ocean floors where mid-ocean ridges occur.
• Fractures are formed on the lithosphere and
magma rises to form new lithosphere on the
ocean floor.
Transform Boundaries
• Transform boundaries occur where two
tectonic plates slip horizontally moving in
opposite directions.
• Occur on both the land and the ocean.
• Transform boundaries cause the lithosphere
to offset which can form shorter segments.
The offsets can appear as a zigzag pattern
when forming mid-ocean ridges.
Tectonic Movement
• The movement of tectonic plates is due to the
flow of heat within the hotter rocks which are in
the mantle.
• The slow moving hotter rocks of the mantle
expand and rise causing the rocks to cool moving
it towards the lithosphere of the Earth.
• The cooler rocks on the lithosphere then sink
below the older lithosphere caused by gravity
then pulls the cooler rocks into the
asthenosphere where the rocks become hotter.
Pangaea
• Is the theory all of the continents of the Earth
were one supercontinent.
• Pangaea means “All Earth”.
• The break up of Pangaea is believed to have
happened through a process call continental drift.
• Pangaea later split into two continents; Laurasia
and Gondwana. These two continents later split
into our current continents of North America,
South America, Europe, Asia, Antarctica,
Australia, Africa.
Continental Drift
• Occurs through a process know as Sea-Floor
Spreading.
• Sea-Floor Spreading is evident at mid-ocean
ridges were magma is release through
fractures in the sea floor.
• Magma cools forming newer crust which in
turn pulls the older crust forming mid-ocean
ridges.
• The sea floor separates as the magma rises
causing the continents to move and separate.
Pangaea
• Existed over 245 million years ago.
• Was surrounded by water on all sides called
Panthalassa.
• Panthalassa means “All Sea”.
• Tectonic plates moved at a rate between 2.5
cm per year and 15 cm per year which
separated Pangaea in order to form Laurasia
and Gondwana.
Laurasia and Gondwana
• Existed about 135 million years ago.
• Separated towards the magnetic pulls of the
North and South poles at first then separated
and expanded East and West to form the
current continents.
• Caused mountains ranges, volcanoes, midocean ridges, and ocean trenches to form.
Current Continents
• Formed about 65 million years ago.
• Collided and separated causing different
species of plants and animals to become
separated, change over time, or to become
extinct.
• Divided the water into five different oceans;
the Pacific Ocean, the Atlantic Ocean, the
Indian Ocean, the Arctic Ocean and the
Southern Ocean.
Earthquakes
• Is the motion of the ground as energy is release
in the mantle or the lithosphere.
• Most earthquakes occur along tectonic plates,
but can occur anywhere on the crust.
• When tectonic plates move they can push or pull
away from each other causing the crust of the
Earth to break and form faults.
• The focus is where the actual earthquake begins.
The epicenter is the location above the focus on
the Earth’s surface.
Faults
• A series of interconnecting faults are called fault zones.
• Fault zones can be different sizes, lengths, and depths
as the cut through the lithosphere.
• When the break in the Earth’s crust is vertical it forms a
fault blocks on either side of the break. The two types
of fault blocks are hanging wall and footwall.
• The are three different types of faults:
– Normal Faults
– Reverse Faults
– Strike-Slip Faults
Normal Faults
• The hanging wall on a fault block will move down
below the footwall of the fault plane.
• The tension of the movement of the tectonic
plates will pull rocks apart.
• Normal faults are generally found at mid-ocean
ridges.
• Normal faults are commonly
associated with divergent
boundaries.
Reverse Faults
• The hanging wall on a fault block will move up
above the footwall of the fault plane.
• The movement of the tectonic plates will push
the rocks together causing compression.
• The compression can cause subduction were the
lithosphere will sink below the asthenosphere.
• Reverse faults are commonly
associated with convergent
boundaries.
Strike-Slip Faults
• The fault blocks move horizontally past each
other.
• The tectonic plates move parallel to the surface
of the Earth.
• The movement will cause shear stress moving
rocks in different directions.
• Strike-Slip faults are commonly
associated with transform
boundaries.
The Focus and The Epicenter
• The focus is located below the Earth’s surface in the
lithosphere.
• The focus is where the
motion of the earthquake
begins.
• The epicenter is the located on
the Earth’s crust above the focus.
• The epicenter is where the largest amount of damage
to the Earth can be seen.
• Scientist can measure the seismic waves of an
earthquake by finding the epicenter.
Seismic Waves
• Seismic waves are measured by the Richter
Scale.
• The strength of the earthquake is measure by
the magnitude.
• The damage causes by the earthquake is by
the intensity.
• There are two types of seismic waves; body
waves and surface waves.
Body Waves
• Body waves occur in the lithosphere.
• Body waves are classified as P Waves and S
Waves.
• P Waves are the primary waves which move
fastest and are detected first because the can
move easily through solids, liquids, and gases.
• S Waves are secondary waves which move
slowly and cannot move through liquids.
Surface Waves
• Surface waves move along the surface of the
Earth and is focused energy where the most
damage will occur.
• Surface waves can be rolling or have up and
down motion. Surface waves can also have a
back and forth motion.
Volcanoes
• Volcanoes can be created at divergent boundaries
or convergent boundaries.
• Volcanoes underground form mid-ocean ridges
also call volcanic mountain chains.
• Volcanic activity which is far away from the
tectonic plate is called a hot spot.
• There are three different types of volcanoes
– Shield Volcanoes
– Cinder Cone Volcanoes
– Composite Volcanoes
Shield Volcanoes
• Shield volcanoes are nonexplosive volcanoes
forming gently sloping sides and cover a large
area.
• The base of a shield volcanoes can measure
more than 100 km in diameter.
• The tallest mountain on Earth is Mauna Kea,
the base of the mountain is on the ocean
floor.
Cinder Cone Volcanoes
• Cinder cone volcanoes are the smallest and
most common of all volcanoes.
• Cinder cone volcanoes have steep sides and a
wide summit crater.
• Most cinder cone volcanoes will only erupt
once in the entire lifetime of the volcano.
• The eruption from a cinder cone volcano is
considered moderate.
Composite Volcanoes
• Eruptions from a composite volcano are highly
explosive.
• Composite volcanoes have a broad base,
slopes which get steeper at the summit, and
smaller summit.
• Composite volcanoes can be active for
hundreds of years with hundreds or
thousands of eruptions.
Volcanoes At Divergent Boundaries
• The tectonic plates move or pull away from
each other.
• The lithosphere is thinner allowing hot molten
rocks, Magma, to reach the Earth’s surface
were it is called Lava.
• Lava from a volcano at a divergent boundary is
usually dark in color and composed of iron
and magnesium.
Volcanoes At Convergent Boundaries
• One tectonic plate will sink below another
tectonic plate causing sea water to be released
into the mantle and crust where the sea water
cools the rocks and the magma rises.
• The eruptions from a convergent boundaries
volcanoes are made up of mantle rocks and
melted crystal rocks and are usually highly
explosive.
• The lava from a convergent boundary tends to be
lighter in cooler and are high in silica and feldspar.
Mountains
• Mountains are formed where plate tectonics
collide or push together usually along a
convergent boundary these mountains are called
folded mountains.
• Mountains can form along fault blocks where the
Earth’s crust drops below other blocks these
mountains are called Fault-Block Mountains.
• Volcanic Mountains are form along convergent
boundaries and can be both on land or in the
ocean.
Folded Mountains
• Folded mountains form were the convergent
boundaries collide.
• The rock layers of the crust push upwards and are
squeezed together where the rocks are uplifted.
• Folded mountains are the most common
mountain forming smooth summits and gentle
slopes.
• The Appalachian Mountains in the Eastern
portion of the United States are an example of
folded mountains.
Fault-Block Mountains
• Fault-Block mountains form were the tension
has been release through the Earth’s crust at a
divergent boundary.
• Fault-Block mountains are formed where large
number of normal faults occur.
• Fault-Block mountains tend to have jagged
summits and steep sides.
• The Tetons in Idaho are an example of faultblock mountains.
Volcanic Mountains
• Volcanic Mountains can be formed on both
the land or the ocean floor.
• On the ocean floor volcanic mountains form
mid-ocean ridges.
• On the land the volcanic mountains are
formed at a subduction zone.
• Mount Shasta in California is a volcanic
mountain.
References
1http://earthguide.ucsd.edu/mystery_detectives/teach/triangulation/images/epicenter_focus.gif (slide 30)
2http://earthsci.org/education/teacher/basicgeol/intro/physproplayers.gif (slide 3)
4http://library.thinkquest.org/17457/platetectonics/apple.jpg (slide 2)
http://office.microsoft.com/en-us/images
5http://www.nature.nps.gov/geology/usgsnps/deform/normfaultLABEL.gif (slide 27)
6http://www.nature.nps.gov/geology/usgsnps/deform/reversefaultLABEL.gif (slide 28)
7http://www.nature.nps.gov/geology/usgsnps/deform/strikeslip.gif (slide 29)
8http://www.oso.tamucc.edu/labs/lab4/Lab4_files/image004.jpg (slide 13)
3www.external.oneonta.edu (slide 40)