Plate Tectonics The Surface of the Earth

Earthquakes

Volcanoes

Plate Tectonics Theory and Pangaea

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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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)

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Comparing the Chemical Composition of the Earth to the Physical Properties of the Earth

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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.

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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

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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.

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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.

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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.

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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. BACK NEXT

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.

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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.

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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.

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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, mid-ocean ridges, and ocean trenches to form.

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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. BACK NEXT

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. NEXTBACK

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 NEXTBACK

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. NEXTBACK

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.

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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.

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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. NEXTBACK

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.

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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.

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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.

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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 NEXTBACK

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.

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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.

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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.

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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.

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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.

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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. NEXTBACK

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.

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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 fault-block mountains. NEXTBACK

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.

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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)

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