Download Volcano Earthquake Notes

Plate Tectonics
Evolution of the Earth
Free powerpoints at http://www.worldofteaching.com
Interior
Inner Core
Outer Core
Lower Mantle
Upper Mantle
Crust
Interior
1220 km
2259 km
2851 km
What’s in the Earth’s Layers:
Crust: is made up of Silicates which are coolerrigid rock
Mantle:
-made up softer weaker rock that can flow slowly.
Core:
-Outer core: liquid metal and very hot!
-Inner core: solid metal and very high pressure!
Volcanoes
• Volcanoes are the result of hot spots within the
crust or mantle of the earth.
• The hot, liquid rock will break through weak spots
in the surface and form volcanoes or flood
basalts. These are called Effusive/Quiet Volcanoes
• Many volcanoes do not release lava, instead they
spit ash. These are called Explosive Volcanoes
• The type of volcano is determined by the
materials in it. Go to:
http://www.nationalgeographic.com/forcesofnature/interactive/index.html
Volcanoes
Fill in the following table to determine how quiet and
explosive volcanoes differ:
Dissolved
Gases
Silica
Content
High
High
High
Low
Low
High
Low
Low
Type of Volcano
Looks like….
Effusive or
Explosive
Volcanoes
Quiet
lava
flows
Volcanoes
Mt. St. Helen before the explosive eruption
Volcanoes
Volcanoes
Time lapse of the eruption
Volcanoes
Mt. St. Helen after the eruption
Volcanoes
Mt. St. Helens begins the rebuilding process
Flood basalts: When volcanic
eruptions coats a thick layer of cooled
magma over the surface of the earth.
This is
IGNEOUS
ROCK.
Igneous
Rock is a
type of
rock that is
made in the
mantle
Volcanoes
Where does the energy to make a Volcano
come from?
The earth’s core is extremely
HOT!
Magma in the mantle is
always moving in the
earth because of the
Earth’s Core, which
causes Convection:
Hot materials rise and
cool materials sink.
• This causes the plates to move with the magma of the mantle
to:
1) move apart
(Divergent
Boundaries) or
• 2) move together
(Convergent
Boundaries)
and even
• 3) past one another (Transform Boundaries.)
Because Plates move they cause the
magma to be released through cracks in
the earth’s crust creating volcanoes.
Volcano locations:
Why at these locations?
The answer is
Tectonic Plates
The reason volcanoes occur at specific
locations:
1. Plate Tectonics Move at a Convergent Zone:
(together)
• Convergent Zones: Volcanoes
The reason volcanoes occur at specific
locations:
2. At Divergent Zones:
(a part)
Tectonic Plates
Tectonic Plates
Another source of
evidence is based
on seafloor ages
which get younger
as we approach
sea floor ridges
Pangea
• What is Pangaea?
• Pangaea was a super continent at one time.
• Scientists use the similarity of rock types and fossil types that date to the
same age to support their theory that the continents were connected to
form a super continent.
• The map below give just one example of areas on different continents that
show the same fossils and rock types.
Pangea
Pangea
Pangea
The break up
of Pangea
The reason volcanoes occur at specific
locations:
3. Magma moves to the surface of the earth near a
weak spot and can activate a magma chamber
• http://sio.ucsd.edu/volcano/about/magma.html
4. This can
happen over
a HOTSPOT. The
Hawaiian Islands
have formed
because a plate
moved over a
hotspot.
Mid-Plate Hotspots
What types of energy are taking place to
have a volcano?
• Mechanical Energy:
– Magma moves from the interior earth up to a weak
portion in the earth’s crust.
– Magma also moves out from the volcano.
– Ash and rock can also move out from a volcano like in a
pyroclastic flow.
• Heat Energy
– The earth’s core has large amounts of heat that escape at
the earth’s surface through a volcano
Draw how a volcano works by using words to describe
the process such as: magma, crust, mantle,
mechanical energy, heat energy
Earthquakes
• Earthquakes are a result of motion within the
earth.
• This only occurs where the earth is solid and
therefore can only occur within about 100
miles of the surface
• Earthquakes provide the best evidence
regarding the interior structure of the Earth.
Earthquakes
Earthquakes
Earthquakes
Earthquakes
A. Where the earthquake
occurs
B. Directly above the
earthquake
C. Where the land masses
move past one another
D. Where the land will either
drop down, jet up or change
along the fault.
E. Waves that move outward
causing the shaking
movement of the earth.
Waves fall under two
categories:
1) P-Waves: occurs when
fault moves past each
other horizontally, cause
a compressed wave.
2) S-Waves: occurs when
faults move vertically,
causes a wavy wave.
* Both display Mechanical
Energy!
Both Body
Waves and
Surface Waves
will differ in
both S & P
Waves:
Seismograph: Measures movement in the
earth.
Finding an Earthquake’s Epicenter
Earthquakes occur often!
Earthquakes occur at plate boundaries more frequently
Location of worldwide earthquakes
Earthquakes
Earthquakes by depth.
Notice that the deep earthquakes occur only at subduction zones.
• The bigger the magnitude of the
earthquake, the more mechanical
energy there is.
•
Go to: http://www.nationalgeographic.com/forcesofnature/interactive/index.html
• Fill out the following table:
Bed rock
Low
High
Fault
Low
High
Land fill
Low
High
Description of Damage
Different Forms of Energy In the Earth
• Mechanical Energy: Energy due to motion
• Heat energy: energy due to heat
• Potential energy: energy that is built up but
not yet released
• Kinetic Energy: energy that is occurring (in
motion)
Tectonic Plates
Tectonic Plates
Today plate boundaries are determined by examining
the location of volcanoes and earthquakes.
Volcanoes result from the friction (heat) of the plates
motion.
Earthquakes occur where plate rub against one another
Plate Boundaries
• Convergent – plates move toward one
another
• Divergent – plates move away from each
other
• Transform – plate moves sideways from
each other
Faults occur at these Plate boundaries, where
land masses move. These faults when moved
release energy in the form of an earthquake.
There are 3 different faults:
1. Normal Fault: as stress
is pulled away on the
plates, one land mass
slips down. (Divergent
Plate boundary)
2. Reverse Fault: as two
plates come together
one land mass jets up
above the other making
a hanging wall.
(Convergent Plate
Boundary)
3. Transverse Fault:
occurs as two plates
slide past one
another. (Transform
plate boundary)
Tectonic Plates
Volcanoes
Tectonic Plates
Tectonic Plates
Tectonic Plates
Tectonic Plates
Another source of
evidence is based
on seafloor ages
which get younger
as we approach
sea floor ridges
Tectonic Plates
Our final piece of
evidence is the
magnetic record
of the ocean floor.
This shows the
pattern of reversal
and we find a near
perfect mirror image
on opposing sides
of the ridge
Tectonic Plates
Tectonic Plates
Tectonic Plates
Composition vs. Motion
We can look at the interior of the Earth based
on the composition of the rocks or based on the movement
Based on Composition
• Crust – solid, relatively low density silicate rock
• Mantle – Semi fluid, denser, mafic (iron and magnesium
bearing) rocks
• Core – Liquid then solid iron and nickel with traces of
heavier elements
Plate Types
• Oceanic plates: basalt
– Dark (black) and dense rock
type composed of silicates,
iron and magnesium
• Continental plates – granite
and andesite
– Light colored (pink, white and
gray) and low density rock
type composed almost
entirely of silicates.
Plate Boundaries
Plate Boundaries
Convergent Plates
Convergent Plates
Convergent Plates
Convergent Plates
The only subduction zone
in the Atlantic
Convergent Plates
Black arrows show subduction zones and
the direction of plate movement
Convergent Plates
Looking at the depth
of earthquakes shows
that angle that the
plate is being subducted
Divergent Plates
Divergent Plates
Divergent Plates
Divergent Plates
Transform Plates
Mid-Plate Hotspots
Mid-Plate Hotspots
Transform Plates
San Andreas
Fault
Mid-Plate Hotspots
Mid-Plate Hotspots
Why do the Plates Move?
Why do the Plates Move?
• No single idea explains everything but we can
identify several forces that contribute to the
movement of the plates.
– Slab pull
• The sinking of the cooled dense oceanic plates pulls on the rest of
the plate
– Ridge rises
• The material deposited on the top of the ridge slides downs from
the rise pushing on the plate
– Convection
• Movement within the mantle could be part of the driving force
behind the motion of the plates.
The Big Picture
Pangea
• What is Pangaea?
• Pangaea was a super continent at one time.
• Scientists use the similarity of rock types and fossil types that date to the
same age to support their theory that the continents were connected to
form a super continent.
• The map below give just one example of areas on different continents that
show the same fossils and rock types.
Pangea
Pangea
Pangea
The break up
of Pangea
Where are we going?
We appear to be headed for another
super continent as North America,
South America, Asia and Australia converge in the
ever shrinking Pacific Ocean