Topic: our dynamic earth
Class: 9
Teacher:
Students name:
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We will learn about:
Plate Tectonics
Plate tectonics is the theory that Earth's outer layer is made up ofChoose an item., which have moved throughout
Earth's history. In the past 25 years, scientists have developed a Choose an item. -- called plate tectonics -- that
explains the locations of volcanoes and their relationship to other large-scale geologic features. The theory explains
the how and why behind mountains, volcanoes, and Choose an item., as well as how, long ago, similar animals could
have lived at the same time on what are now widely separated continents. Exactly what drives plate tectonics is not
known. One theory is that convection within the Earth's mantle Choose an item. the plates, in much the same way
that air heated by your body rises upward and is deflected sideways
when it reaches the ceiling.
The story of plate tectonics really starts deep within the Earth, so lets
take a look inside first. Although the Earth appears to be made up of
solid rock it’s actually made up of three distinct layers: the crust, mantle,
and core. Each layer has its own unique properties and chemical
composition.
LAYERS OF THE EARTH:
Crust
Crust - The Earth's outermost surface is called the crust. The crust is typically about 25 miles thick beneath
continents, and about 6.5 miles thick beneath oceans. The crust is relatively light and brittle. Most earthquakes
occur within the crust. The crust in this image is much smaller in the real earth!
Mantle
Mantle - The region just below the crust and extending all the way down to the Earth's core is called the mantle. The
mantle is relatively flexible so it flows instead of fracturing.
Core
Core - Beneath the mantle is the Earth's core. The Earth's core consists of a fluid outer core and a solid inner core.
Because the outer core contains iron, when it flows it generates a magnetic field. This is the source of the Earth's
magnetic field.
Read the definitions, then label the diagram below.
Definitions
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Crust - the rigid, rocky outer surface of the Earth, composed mostly of basalt and granite. The
crust is thinner under the oceans.
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Inner core - the solid iron-nickel center of the Earth that is very hot and under great pressure.
 Mantle - a rocky layer located under the crust - it is composed of silicon, oxygen, magnesium,
iron, aluminum, and calcium. Convection (heat) currents carry heat from the hot inner mantle to
the cooler outer mantle.
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Outer core - the molten iron-nickel layer that surrounds the inner core.
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TECTONIC PLATES
The outer surface of the earth is made of 12 major plates and several smaller plates. The plates are all
moving in different directions and at different speeds (from 2 cm to 10 cm per year--about the speed at
which your fingernails grow) in relationship to each other. The plates are moving around like cars in a
demolition derby, which means they sometimes crash together, pull apart, or sideswipe each other.
The place where the two plates meet is called a plate boundary. Boundaries have different names
depending on how the two plates are moving in relationship to each other. These plates move towards
each other (convergent boundaries), away from each other (spreading or divergent boundaries), or slide
past each other (transform boundaries).
Questions
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5.
6.
Plates can crash together, pull apart or Click here to enter text.?
At what speeds to the plates move each year? Click here to enter text.
What is the name of the place where two plates meet? Click here to enter text.
When plates move toward each other we call this a Choose an item.
When plates move away from each other we call this a spreading or Choose an item.
When plates slide past each other we call this a Choose an item.
The tectonic plates are made up of Earth’s crust and the upper part of the mantle layer
underneath.
Together the crust and upper mantle are called the
80 km deep.
lithosphere and they extend about
The lithosphere is broken into giant plates that fit around the globe like puzzle pieces.
These puzzle pieces move a little bit each year as they slide on top of a somewhat fluid part
of the mantle called the asthenosphere. All this moving rock can cause
earthquakes.
The asthenosphere is ductile and can be pushed and deformed like silly putty in response
to the warmth of the Earth. These rocks actually flow, moving in response to the stresses
placed upon them by the churning motions of the deep interior of the Earth. The flowing
asthenosphere moves the lithosphere of the Earth (tectonic plates), including the
continents.
1. What parts of the Earth is Lithosphere made up of?
2. What part of the Earth do the Tectonic plates sit on?
Label the Volcano Diagram
Use the definitions to label the diagram below.
Definitions
ash cloud - an ash cloud is the cloud of ash that
forms in the air after some volcanic eruptions.
magma chamber - a magma chamber contains
magma (molten rock) deep within the Earth's crust.
conduit - a conduit is a passage through which
magma (molten rock) flows in a volcano.
side vent - a side vent is a vent in the side of a
volcano.
crust - the crust is Earth's outermost, rocky layer.
vent - a vent is an opening in the Earth's surface
through which volcanic materials erupt.
lava - lava is molten rock; it usually comes out of
erupting volcanoes.
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Research
Research, using the internet how volcanoes form.
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VOLCANOES
Volcanoes are not randomly distributed over the Earth's surface. Most are concentrated on the edges of continents,
along island chains, or beneath the sea forming long mountain ranges. More than half of the world's active
volcanoes above sea level encircle the Pacific Ocean to form the circum-Pacific "Ring of Fire."
‘Ring of fire’
Read the following article (from http://www.crystalinks.com/rof.html):
The Ring of Fire is a zone of frequent earthquakes and volcanic eruptions that encircles the basin of the Pacific
Ocean. It is shaped like a horseshoe and it is 40,000 km long. It is associated with a nearly continuous series of
oceanic trenches, island arcs, and volcanic mountain ranges and/or plate movements. It is sometimes called the
circum-Pacific belt or the circum-Pacific seismic belt.
90% of the world's earthquakes and 81% of the world's largest earthquakes occur along the Ring of Fire. The next
most seismic region (5-6% of earthquakes and 17% of the world's largest earthquakes) is the Alpide belt which
extends from Java to Sumatra through the Himalayas, the Mediterranean, and out into the Atlantic. The Mid-Atlantic
Ridge is the third most prominent earthquake belt.
The Ring of Fire is a direct consequence of plate tectonics and the movement and
collisions of crustal plates.
Major volcanic areas in the Ring of Fire
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In South America the Nazca plate is colliding with the South American plate. This has created the Andes and
volcanoes such as Cotopaxi and Azul.
In Central America, the tiny Cocos plate is crashing into the North American plate and is therefore
responsible for the Mexican volcanoes of Popocatepetl and Paricutun (which rose up from a cornfield in
1943 and became a instant mountains).
Between Northern California and British Columbia, the Pacific, Juan de Fuca, and Gorda plates have built the
Cascades and the infamous Mount Saint Helens, which erupted in 1980.
Alaska's Aleutian Islands are growing as the Pacific plate hits the North American plate. The deep Aleutian
Trench has been created at the subduction zone with a maximum depth of 25,194 feet (7679 meters).
From Russia's Kamchatka Peninsula to Japan, the subduction of the Pacific plate under the Eurasian plate is
responsible for Japanese islands and volcanoes (such as Mt. Fuji).
The final section of the Ring of Fire exists where the Indo-Australian plate subducts under the Pacific plate
and has created volcanoes in the New Guinea and Micronesian areas. Near New Zealand, the Pacific Plate
slides under the Indo-Australian plate.
Watch the DVD ‘Ring of Fire’
In your own words outline the Ring of Fire
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HOT SPOTS
Watch the animation below:
http://www.wwnorton.com/college/geo/egeo2/content/animations/2_6.htm
1. Explain why a hot spot causes volcanoes to form in a line.
2. Why do volcanoes formed from a hot spot eventually become extinct?
3. The Hawaiian Islands are a chain of islands formed from a hot spot. Find a picture of the Hawaiian Islands
and insert it below.
Plate tectonics learning objects.
A. Tectonic Investigator.
go to http://www.scootle.edu.au/ec/pin and type in the pin RDDHUJ to open the learning object titled “Tectonic
investigator”
As you work through the learning object do the following:
1. Next to each of the pictures below describe how the slinky moves for each type of wave.
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2. Complete the following statements:
a. P waves travel through both Click here to enter text. and liquids.
b. S waves only travel through Click here to enter text.
c. When a big earthquake occurs Click here to enter text. waves can eventually be detected on
the opposite side of the Earth but Click here to enter text. do not reach the opposite side of
the Earth. This suggests that the Earth contains some Click here to enter text. .
3. When you have fitted all the tectonic plates together take a screen shot and paste it into your notes.
Write a caption for the screen shot.
4. Take a screen shot showing convection currents in the mantle and write a caption for the image.
B. Tectonic boundaries.
Go back to http://www.scootle.edu.au/ec/pin and this time type in the pin KNJEXA to open the learning object
tiled “Tectonic boundaries”
Complete the following summary as you work
through the learning object:
1. The type of plate boundary shown in
the picture on the left is a Click here to enter
text. plate boundary. The plates are moving
2.
3.
4.
5.
Click here to enter text. and new ocean is being formed as melted rock from Click here to enter text.
the rises up to fill the gap between the two plates.
The plates shown in the animation are moving at a rate of about Click here to enter text. a year.
At this type of plate boundary the rocks closer to the boundary are Click here to enter text. than the
rocks further away.
Over time an under water Click here to enter text. forms at this type of plate boundary.
There is a divergent plate boundary running through the island called Click here to enter text.. This
island is gradually Click here to enter text. as new rock forms at the boundary. On this island there
are Click here to enter text. and Click here to enter text. in the ground.
Now select Convergent at the top of the screen.
1. At this type of plate boundary the
plates are moving Click here to enter text.each
other. The plates shown are moving at a rate
of about Click here to enter text. cm a year. One
plate is forced down into the hot Click here to
enter text. and starts toClick here to enter text.
. Some of the molten rock rises up through the
continental crust under pressure and form a
Click here to enter text. . Click here to enter text.
and Click here to enter text. can also result from
subduction (subduction = one plate sinking under another).
2. Along the coast of South America the Click here to enter text. plate is sinking under the Click here to
enter text. plate. This has resulted in the formation of a Click here to enter text. along the coast and
the Click here to enter text. mountain range on land.
3. Where the Indian and Eurasian plates meet there is also a Click here to enter text. plate boundary.
The plates are being pushed Click here to enter text.. Because the two plates are of similar Click here
to enter text. neither plate sinks under the other. Instead they Click here to enter text. into each other
and Click here to enter text. . A Click here to enter text. range forms.
4. To the South East of Australia the Pacific plate is Click here to enter text. under the Australian plate.
This has resulted in the formation of a chain of Click here to enter text. islands. Tsunamis and Click
here to enter text. are also likely in this region.
Now select transform plate boundary.
1. At a transform plate boundary two plates are moving Click here to enter text.each other. At the
boundary between the North American and Pacific plate the plates are moving at a rate of about
Click here to enter text. a year. As the two plates slide past each other they get Click here to enter
text.. When they suddenly become unstuck an Click here to enter text. results.
2. When there is transform boundary under the ocean Click here to enter text. may result but Click here
to enter text. are unlikely to result because these are the result of the ocean floor moving up and
down rather than sideways.