ECVHS Modeling Plate Tectonics Questions

1General Science I A
Credit 2
Rev. 5/5/21
NAME:_________________________
CREDIT 2A: MODELING PLATE TECTONICS
Learning Goal for this Credit
Design an investigation or model using appropriate scientific tools, resources and methods.
Lesson
Title
INTRODUCTION
2.1
Earth’s Structure
2.2
Continental Drift and Plate Tectonics
2.3
Reshaping Earth’s Crust
PERFORMANCE TASK
QUIZ
Assignments
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 Connect to Essential Question
 Exploration Activity
 Reading and Questions
 Videos (optional)
 Earth’s Layers Concept Map
 Review Questions
 Connect to Prior Knowledge
 Exploration Activity
 Reading and Questions
 Videos (optional)
 Plate Boundaries
 Review Questions
 Connect to Prior Knowledge
 Exploration Activity
 Reading and Questions
 Videos (optional)
 Mapping Plate Boundaries
 Analysis Questions
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Student Support Icons
Title
Icon
Description
Review
Activity
This provides the students with a reminder that they need to answer questions.
Technology
Guides students through the tasks and assignments that require the use of
technology and manipulatives.
Reading
This icon lets the students know they will be completing a reading activity.
Credit Materials
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Materials
Pen/Pencil
HMH Earth Science
Textbook (optional)
Packet
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Technology Needs
Internet
Computer
HMH Online Resources
(optional)
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NAME:_________________________
CREDIT 2A: INTRODUCTION
Read “What’s in the Center of the Earth?” and watch the video “The Mystery of Earth’s Core Explained”
below. Then answer the essential question.
What’s in the Center of the
Earth?
One of the most distinctive features of the
Earth’s interior is how it appears layered by
density, with the heaviest material in the
center and the lightest material at the
surface. In fact, the Earth probably looks
similar to a hardboiled egg if you could cut
it open. The yellow material in the center
(the yolk) of the egg represents Earth’s
core. Most scientists believe that the Earth’s
core is composed of dense materials like
iron and nickel. Next, the egg’s shell is like
the earth’s crust – a thin but rigid, low
density material at the surface. Earth’s crust is made up of pieces called tectonic plates. These plates are in
constant motion, causing Earth’s continents to move. Finally, the white material of the egg represents the
Earth’s mantle – the largest layer in the Earth.
An essential question is something that allows you to explore the content of the credit. Before you answer the
essential question, watch the video. Then, answer the essential question to the best of your ability. You will
revisit the essential question at the end of the credit to see if your answer has evolved.
Video: The Mystery of the Earth’s Core Explained (3:28)

“The Mystery of the Earth’s Core Explained.” YouTube. DNews, 21 Sept. 2013. Web. 26 Jan. 2015.
Essential Question
Do you think mankind will ever reach the center of the Earth? Why or why not?
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General Science I A
Credit 2
LESSON 2.1: EARTH’S STRUCTURE
Learning Goal for this Credit
Design an investigation or model using appropriate scientific tools, resources and methods.
Learning Goals for this Lesson
 Describe the size and shape of Earth.
 Describe the compositional and structural layers of Earth’s interior.
 Identify the possible source of Earth’s magnetic field.
 Summarize Newton’s law of gravitation.
Lesson Assignments
 Connect to Essential Question
 Exploration Activity
 Reading and Questions
 Videos (optional)
 Earth’s Layers Concept Map
 Review Questions
Engage
Connect to Essential Question
If mankind were to drill to the center of the Earth, what do you think they would find?
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Explore
Exploration Activity
The compositional zones of Earth’s interior are
the crust, mantle, outer core, and inner core.
Each zone has unique physical and structural
properties. The crust is the thin, solid, outermost
zone of the Earth. It is approximately 35
kilometers thick. Below the crust is the mantle.
Earth’s mantle is more dense and thicker than the
crust. It is approximately 2,900 kilometers thick.
The outer core lies beneath the mantle and is
hypothesized to be liquid in composition. It is
2,250 kilometers thick. Finally, the inner core is
believed to be solid and is 1,250 kilometers thick.
Crust
Using the diagram to the right, fill in the
temperature values for the depth distances given in
the table below. The first row is completed for you
as an example.
Zone
Depth (Kilometers)
Temperature (oC)
Crust
1 km
25oC
Mantle
1,000 km
Outer Core
4,000 km
Inner Core
6,000 km
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Explain
As you complete the reading, answer the questions in the space provided.
Reading
What Shape is Earth?
Earth formed about 4.6 billion years ago. It is the only planet in our solar system that scientists think has liquid
water on its surface. Earth is the only planet we know of that supports life. If you looked at Earth from space, it
would look like a perfect sphere, or ball. However, Earth is not perfectly round. It is an oblate spheroid, or
flattened sphere similar to the shape of an inflated balloon turned on its side.
What is Inside Earth?
Scientists can study Earth’s interior
directly by drilling. However, scientists
can drill only a few kilometers into
Earth’s surface. To learn about the rest
of Earth’s interior, scientists must use
indirect methods. One way scientists
learn about Earth’s interior is by
studying seismic waves. Seismic
waves are vibrations that travel
through Earth. Earthquakes cause most
seismic waves. Seismic waves move
differently in different substances.
Therefore, by studying these waves,
scientists can learn what Earth’s
interior is made of. Scientists divide Earth’s interior into three compositional zones and five structural zones.
Compositional zones are made up of different materials. The thin, solid, outermost compositional zone is the
crust. Crust beneath oceans is called oceanic crust. Crust that makes up continents is called continental crust.
In general, continental crust is much thicker than oceanic crust. The crust is between 5 km and 35 km thick.
The mantle is the compositional zone that lies beneath the crust. The mantle is made of denser rock than the
crust and is almost 2,900 km thick. The inner- most compositional zone is the core. The core is a sphere with a
radius of about 3,500 km. Scientists think the core is made up mainly of iron and nickel.
Structural zones have different properties. The lithosphere is made up of the crust and the top part of the
mantle. The lithosphere is relatively cool and brittle. The asthenosphere is made of hot, solid mantle rock. The
rock of the asthenosphere is also under a great deal of pressure. The heat and pressure allow the solid rock to
flow. The mesosphere is a layer of solid mantle rock beneath the asthenosphere. The core is divided into the
outer core and inner core. The outer core is made of liquid iron and nickel. Scientists think the inner core is
made of solid iron and nickel.
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1. Why must scientists use indirect methods to study Earth’s interior?
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2. Which three structural zones overlap with the mantle?
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3. How are the inner core and outer core different?
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What Is the Source of Earth’s Magnetic Field?
Earth acts as a giant magnet. Like all magnets, it has two magnetic poles. Earth’s magnetic field extends beyond
Earth’s atmosphere, and it affects a region of space called the magnetosphere. Most scientists think that the
liquid iron in Earth’s outer core is the source of Earth’s magnetic field. They think that motions within the core
produce electric currents that produce the magnetic field.
4. A compass needle is a very small magnet that can move. Why can you use a compass to determine
direction on Earth?
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What Is Newton’s Law of Gravitation?
Gravity is a force that pulls matter together. In the 1600s, Isaac Newton explained how gravity affects objects
in his law of universal gravitation. This law states that the force of gravity between two objects depends on the
masses of the objects and the distance between them. Earth’s gravity pulls objects toward Earth’s center.
Weight is a measure of the strength of this pull. The newton (N) is the SI unit of weight. The mass of an object
does not change with location, but the weight of an object can change.
5. Why would you weigh slightly less on a high mountain peak than you would at sea level?
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Allison, Mead A., et al. “Chapter 2: Earth as a System/Section 1: Earth: A Unique Planet.” Holt McDougal Earth Science Interactive Reader, Holt McDougal, a
Division of Houghton Mifflin Harcourt Publishing Co., 2010, pp. 13-16.
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Videos
If you would like to learn more about this topic, watch the videos below for more information. (Optional)
Structure of the Earth & Its Different Layers

What does the interior of the Earth look like? This visual shows the different layers
of the Earth along with definitions.
“Structure of the Earth & Its Different Layers | Environmental Chemistry | Chemistry | FuseSchool” YouTube. FuseSchool –
Global Education, 8 Oct. 2014. Web. 26 Apr. 2021.
Why Does the Earth Have Layers? (4:51)

“Why Does The Earth Have Layers?” YouTube. It’s OK to Be Smart, 13 Oct. 2014. Web. 18 Sept. 2015.
Why is the Earth made up of multiple layers? How do we know what
Earth’s insides look like even though we have never been there? This
video will explain where Earth’s layers came from and how we know what
they are made of.
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Elaborate
Earth’s Layers Concept Map
Complete the concept map below to show the relationship between Earth’s compositional zones and structural
zones using the following terms. Each term can be found in the reading section for this lesson.
Structural
Compositional
Asthenosphere
Mesosphere
Crust
Mantle
Outer core
Inner core
Allison, Mead A., et al. “Chapter 2: Earth as a System/Section 1: Earth: A Unique Planet.” Holt McDougal Earth Science Interactive Reader, Holt McDougal, a
Division of Houghton Mifflin Harcourt Publishing Co., 2010, pp. 16
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Evaluate
Review Questions
Answer the following questions.
1. On which layer of Earth do we live?
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2. Which 2 layers are included in the lithosphere?
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3. The Earth’s inner core is made up mainly of what 2 substances?
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4. Like an egg, Earth has a core, a layer surrounding the core, and a thin, hard outer layer. Which layers of the
Earth match the layers of an egg?
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LESSON 2.2: CONTINENTAL DRIFT AND PLATE
TECTONICS
Learning Goal for this Credit
Design an investigation or model using appropriate scientific tools, resources and methods.
Learning Goals for this Lesson
 Summarize evidence for the hypothesis of continental drift.
 Describe the process of sea-floor spreading.
 Explain how sea-floor spreading provides a mechanism for continental drift.
 Summarize the theory of plate tectonics.
 Identify and describe the three types of plate boundaries.
 Identify and describe three causes of plate movement.
Lesson Assignments
 Connect to Prior Knowledge
 Exploration Activity
 Reading and Questions
 Videos (optional)
 Plate Boundaries
 Review Questions
Engage
Connect to Prior Knowledge
How do you think Earth’s interior affects what is happening on the surface?
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Explore
Exploration Activity
After mapping the continents, early
explorers noticed the coastlines of
Africa and South America could fit
together like puzzle pieces. In 1912 a
German scientist named Alfred
Wegener proposed a hypothesis to
explain this called continental drift.
Wegener proposed that the continents
once formed part of a single landmass
called a supercontinent. Around the
Mesozoic Era (200 million years ago),
the supercontinent began to break
apart and the continents started drifting
to their current locations. Evidence
from fossils and rock formations today
support this theory. Examine the map
to the right. This map shows fossil
and rock formation evidence for the
hypothesis of continental drift.
Use the map to answer the questions.
1. According to the map, which continents have mountains that formed around 410 million years ago?
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2. Which continents have mountains that formed around 250 million years ago?
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3. Which continents contain fossils of Mesosaurus?
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4. Which continents contain fossils of Glossopteris?
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5.
6. ?
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Allison, Mead A., et al. “Chapter 10: Plate Tectonics/Section 1: Continental Drift.” Holt McDougal Earth Science Interactive Reader, Holt McDougal, a Division of
Houghton Mifflin Harcourt Publishing Co., 2010, pp. 141
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Explain
As you complete the reading, answer the questions in the space provided.
Reading
What is Continental Drift?
Alfred Wegener was a German scientist who studied maps of the continents. He noticed that some of the
continents seem to fit together like puzzle pieces. For example, he thought that South America and Africa look
like they could fit together. The shapes of the continents gave Wegener an idea. He thought that the continents
looked like they could fit together because they were once joined together. He made a hypothesis that the
continents were once joined together into a single large continent. He called this large continent a
supercontinent. Wegener thought that the supercontinent began to break apart about 200 million years ago.
Over time, the pieces slowly moved apart. They became the continents that we see today. Wegener’s hypothesis
is now known as continental drift.
What Is the Evidence for Continental Drift?
The matching shapes of the continents support the idea of continental drift. However, there are also other pieces
of evidence that support the hypothesis. These pieces of evidence include the following:
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fossil evidence
rock evidence
climate evidence
Some evidence that the continents were once joined comes from fossils. Remember that fossils are signs that
living things once existed in an area. Wegener learned that fossils of similar animals and plants exist on
continents that are far apart today. For example, fossils of Mesosaurus, an ancient animal, are found in South
America and Africa. The fossils on both continents are identical. The fossils show that Mesosaurus lived on
both continents at about the same time. If the continents were always separate, like they are today, then
Mesosaurus would have had to travel between them. It could not have swum such a long distance. There is no
evidence that the continents were connected by land bridges that reached across the oceans. Therefore,
Mesosaurus probably could not have traveled between separated continents. However, if the continents were
once joined, Mesosaurus could have lived on the supercontinent. When the supercontinent broke apart, fossils
remained on both of the new continents. Therefore, the Mesosaurus fossils and other similar fossils provide
evidence for continental drift.
Rocks also provide evidence for continental drift. Similar rocks exist on continents that are far apart today.
Some mountains that exist on one continent seem to continue on another continent. If the continents were once
joined together, these similar rocks would line up. They would form long mountain chains. Therefore, the rocks
at different places on Earth’s surface give evidence that the continents were once joined.
Scientists think some of the continents had different climates long ago than they have today. They have found
signs that glaciers once existed in South America and Africa. A glacier is a huge, slow-moving river of ice.
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Today, most of South America and Africa are too hot for glaciers to form. If the continents were once closer to
Earth’s poles, they might have been much colder. Scientists have also found evidence that Antarctica once had
a much warmer climate. They have found fossils of tropical plants in Antarctica. If Antarctica had been closer
to the equator at one time, its climate would have been warmer. Therefore, the evidence for ancient climates
supports the idea that the continents have moved.
Wegener had a lot of evidence to support the idea that the continents were once joined. However, he could not
explain how they might have moved. He thought that the continents might push through the ocean crust. Other
scientists showed that was impossible. Therefore, most scientists did not accept Wegener’s hypothesis.
1. How do fossils support the continental drift hypothesis?
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What Is Sea-Floor Spreading?
Wegener and other scientists living
during the early 1900s thought that the
ocean floor was smooth and flat. They
thought it was all the same age and did
not change very much over time.
However, in the 1940s and 1950s,
scientists began to learn that this idea is
not true. Scientists found long
mountain ranges on the ocean floor.
Many of these mountains run through
the middle of the oceans. Therefore,
scientists called them mid-ocean ridges.
As scientists studied the mid-ocean
ridges, they learned two surprising facts.
First, they learned that the sediment on
the ocean floor is much thinner near a
ridge than far from it. Sediment on the
ocean floor is made of dirt, dust, and
pieces of shells. The older the ocean
floor is, the thicker the layer of
sediment there is. Rocks at the middle
of the ridge have thinner layers of
sediments than rocks farther from the
ridge. Therefore, rocks at the middle of
the ridge are probably younger.
Second, scientists found that the rock of
the ocean floor is much younger than
they thought. None of the rock on the
ocean floor is older than 200 million years. (The oldest rocks on land are more than 4 billion years old.) Using
radiometric dating, they also found that the rock near the ridge is younger than the rock farther away.
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In the late 1950s, a scientist named Harry Hess made a new hypothesis. He knew that there are rifts, or valleys,
running through the middle of mid-ocean ridges. He hypothesized that those rifts are cracks in Earth’s crust. He
thought that magma, or melted rock, could form below the crust and push up through the rift. When the melted
rock cools and hardens, it forms new ocean crust. The new crust forming at the rift makes the ocean floor
wider. In other words, new crust pushes apart, or spreads, the sea floor on each side of the rift. Therefore, the
process is known as sea-floor spreading. Sea-floor spreading makes the ocean floor on the two sides of a rift
move apart. Hess thought that the moving sea floor might carry the continents. If that happened, then sea-floor
spreading could explain how the continents move. Sea-floor spreading therefore gave more evidence for the
continental drift hypothesis.
2. How does sea-floor spreading support the hypothesis of continental drift?
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What Is the Other Evidence for Sea-Floor Spreading?
As scientists studied the ocean floor in the 1950s and 1960s, they found more evidence for sea-floor spreading.
One strong piece of evidence for sea-floor spreading is based on paleomagnetism. Paleomagnetism is the
study of the magnetic properties of ancient rocks. You probably know that you can use a compass to find which
way is north. Most compass needles have one end painted red. The needle on the compass will spin until the red
end points toward the north pole. A compass needle is a small magnet. It points north because Earth acts like a
giant magnet. Like a magnet, Earth has a north magnetic pole and a south magnetic pole. The red end of the
needle is attracted to Earth’s northern magnetic pole. Earth’s magnetic poles do not line up perfectly with the
geographic poles. In other words, the needle of a compass does not point to the actual North Pole. It points to an
area near the North Pole. The area a compass needle points to is known as the north geomagnetic pole.
Earth’s magnetic poles have not always been where they are today. Many times in the past, they have changed
places. The northern magnetic pole moved to the south, and the southern magnetic pole moved to the north.
Scientists call the times when the poles were in opposite places magnetic reversals. During a magnetic
reversal, a compass needle points south, not north.
Scientists have learned that some minerals are magnetic. They act like tiny compasses. When rock melts, the
minerals can line up with Earth’s magnetic field. When the melted rock cools and hardens, the minerals are
stuck in place. If a magnetic reversal happens after the rock cools, the minerals cannot move to line up with the
new magnetic field. Therefore, the rocks can show what Earth’s magnetic field was like when they formed.
Rocks that contain iron-rich minerals have magnetic properties. Scientists can study these properties to learn
about Earth’s magnetic field in the past. The study of these properties is called paleomagnetism.
Paleomagnetism gives more evidence for sea-floor spreading. When scientists study the magnetic fields in
the rocks on the sea floor, they see a pattern. The rocks close to a mid-ocean ridge have normal magnetic fields.
Farther from the ridge, the rocks have reversed magnetic fields. Even farther out, the fields are normal again.
The pattern of normal and reversed fields is the same on both sides of the ridge. As new crust forms at a midocean ridge, the magnetic minerals line up with Earth’s magnetic field. The older crust moves away from the
ridge as new crust forms. When a magnetic reversal happens, the minerals in the new crust line up with the
reversed magnetic field. However, the minerals in the older crust cannot move. They are frozen in place. Over
time, “stripes” of rock form with normal and reversed magnetic fields.
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3. What did scientists observe when they studied the magnetic fields of rocks on the sides of mid-ocean
ridges?
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What Is Plate Tectonics?
After Harry Hess described the idea of sea-floor spreading, scientists found more evidence that continents can
move. They used the evidence to develop a new theory: the theory of plate tectonics. The theory of plate
tectonics explains how continents move and change shape. Remember that Earth’s outer layer is called the
crust. The layer underneath the crust is called the mantle. The top part of the mantle is very stiff and brittle.
Together, the crust and this upper, stiff part of the mantle form the lithosphere. The lithosphere includes only
the very top part of the mantle. The layer of the mantle below the lithosphere is called the asthenosphere.
Unlike the rock in the lithosphere, the rock in the asthenosphere is soft. It is solid, but it is so hot and soft that it
can flow, like chewing gum. Scientists say that the asthenosphere is made of plastic rock. Plastic means
“flexible and able to flow.” The lithosphere is broken up into large pieces called tectonic plates. The tectonic
plates move slowly over the asthenosphere. As the tectonic plates move, they carry the continents with them.
Therefore, the movement of tectonic plates explains the movement of continents.
What Happens Where Tectonic Plates Touch?
Tectonic plates are like puzzle pieces. The places where they touch are called plate boundaries. Earthquakes and
volcanoes are more common at plate boundaries than anywhere else. At plate boundaries, tectonic plates rub
together. The plates do not rub together smoothly, though. Instead, they stick together, like two pieces of
sandpaper. The movements of the plates cause pressure on the plate boundaries. When the pressure gets too
high, the rock breaks. The breaking rock releases energy that makes the ground shake. The shaking is an
earthquake. Almost all earthquakes happen at plate boundaries. Scientists have special tools that can record
where earth- quakes happen. They can draw those locations on a map. When they draw the locations on a map,
they see that most earthquakes happen in certain areas. These areas are the same as the plate boundaries.
Volcanoes are also more common on plate boundaries. Like earthquakes, volcanoes are most common in certain
areas. The areas where earthquakes and volcanoes are most likely show where the plate boundaries are. Not all
plate boundaries are the same. There are three types of plate boundaries:
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divergent boundaries, where plates move apart.
convergent boundaries, where plates move together.
transform boundaries, where plates slide past each other.
4. What is a tectonic plate?
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What Happens at a Divergent Boundary?
To diverge means “to move apart.”
At a divergent boundary, two plates
move away from each other. Midocean ridges are divergent
boundaries. However, divergent
boundaries can also form on land.
Divergent boundaries are places
where new lithosphere forms. At a
mid-ocean ridge, melted rock, or
magma, rises up from the
asthenosphere. It flows into the rift
between the plates. When the magma
cools and hardens, it forms new
lithosphere.
What Happens at a Convergent
Boundary?
To converge means “to come
together.” At a convergent
boundary, two plates move toward
each other. In other words, the plates
collide. The collision of the plates
can have different effects. The
effects of the collision depend on
what kinds of lithosphere are
colliding. There are two main types
of lithosphere: oceanic lithosphere
and continental lithosphere. Oceanic
lithosphere is thin and dense.
Continental lithosphere is thick and
not very dense.
At some convergent boundaries,
oceanic lithosphere meets continental
lithosphere. The oceanic lithosphere
is denser than the continental
lithosphere. Therefore, the oceanic lithosphere sinks beneath the continental lithosphere. The oceanic
lithosphere sinks into the asthenosphere. The sinking of the lithosphere into the asthenosphere is called
subduction. As part of the lithosphere sinks into the asthenosphere, the heat and pressure on the lithosphere
become greater. The high heat and pressure squeeze water out of the sinking lithosphere. The water mixes with
the rock in the asthenosphere and makes the rock melt. The melted rock rises through the crust and erupts. Thus,
volcanoes are common at plate boundaries where oceanic lithosphere sinks beneath continental lithosphere. As
the oceanic lithosphere sinks, it rubs against the continental lithosphere on the other plate. The rubbing produces
pressure that can make the rock slip and break, causing earthquakes. Thus, large earthquakes are common at
plate boundaries where oceanic lithosphere collides with continental lithosphere.
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At some convergent boundaries, two pieces of continental lithosphere collide. Because continental lithosphere
is not very dense, it does not easily sink into the asthenosphere. Therefore, when two pieces of continental
lithosphere collide, both pieces crumple up and form very tall mountains. The tallest mountains in the world, the
Himalaya Mountains, are found at this kind of convergent boundary. Volcanoes are not very common at this
type of convergent boundary. Earthquakes are common. However, the earthquakes are not as large as those at
continental-oceanic boundaries.
At some convergent boundaries, oceanic lithosphere meets oceanic lithosphere. Subduction happens at these
convergent boundaries. One of the pieces of oceanic lithosphere sinks beneath the other one. The sinking
lithosphere gives off water, just like at a continental-oceanic convergent boundary. The water causes the
asthenosphere to melt and form magma. The magma rises through the lithosphere and erupts. Therefore,
volcanoes are common at oceanic- oceanic convergent boundaries. Earthquakes are also common, because of
the pressure produced when the sinking lithosphere rubs against the other lithosphere. An island arc is a chain
of volcanic islands. Island arcs are common at this kind of convergent boundary. Japan is an example of an
island arc.
What Happens at a Transform Boundary?
At a transform boundary, two tectonic plates slide past each other. As the plates slide past each other, they
stick and press together. When the pressure gets too high, the rock breaks and causes an earthquake. Therefore,
earthquakes are common at transform boundaries. Volcanoes are not common at transform boundaries. The
San Andreas fault in California is an example of a transform boundary. Transform boundaries are also common
along mid-ocean ridges. Transform boundaries break most mid-ocean ridges into short segments.
5. What are the three types of plate boundaries?
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What Makes Tectonic Plates Move?
Scientists are still not sure why the tectonic plates move.
However, they think that three main factors cause the plates to
move. Those three factors are mantle convection, ridge push, and
slab pull. Suppose you put a pot of water on a hot stove. The
water at the bottom of the pot will heat up first. As it heats up, it
becomes less dense. The less dense water rises to the top of the
pot. Cooler, denser water sinks toward the bottom to replace the
rising water. The movement of the water is an example of
convection. During convection, denser material sinks, and less
dense material rises. Scientists think the rock in Earth’s mantle
can convect, just like the water in the pot. Hot rock rises toward
the surface, and colder rock sinks. Scientists think the movement
of the mantle might be one of the reasons the plates move. As the
mantle moves, it may carry the plates along.
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Convection in the mantle is not the only reason the plates move. At mid-ocean ridges, new crust forms. The new
crust pushes the older crust away from the ridge. This process is called ridge push. Scientists think ridge push
might also cause plates to move. Most scientists think that mantle convection and ridge push cause only a little
bit of plate motion. They think pulling forces where plates converge are the main forces that make the plates
move. Subduction happens at most convergent boundaries. Remember that during subduction, one plate sinks
into the asthenosphere. Scientists think that, as the edge of the plate sinks, it pulls the rest of the plate along with
it. This process is called slab pull.
6. Explain mantle convection.
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
Allison, Mead A., et al. “Chapter 10: Plate Tectonics/Section 1: Continental Drift.” Holt McDougal Earth Science Interactive Reader, Holt McDougal, a Division of
Houghton Mifflin Harcourt Publishing Co., 2010, pp. 139-146.
Allison, Mead A., et al. “Chapter 10: Plate Tectonics/Section 2: The Theory of Plate Tectonics.” Holt McDougal Earth Science Interactive Reader, Holt McDougal, a
Division of Houghton Mifflin Harcourt Publishing Co., 2010, pp. 147-154.
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Videos
If you would like to learn more about this topic, watch the videos below for more information. (Optional)
Alfred Wegener: Great Minds (4:54)

“Alfred Wegener: Great Minds.” YouTube. SciShow, 4 Apr. 2012. Web. 22 May 2014.
Who was Alfred Wegener? How did he discover continental drift? This video
talks about the discoveries of Alfred Wagener and the difficulties he had
convincing the scientific community that continental drift was in fact
happening.
Plate Tectonics (9:21)

“Plate Tectonics.” YouTube. Bozeman Science, 22 May 2011. Web. 27 Jan. 2015.
How do plate tectonics shape our planet? What are the differences between
continental and oceanic plates? Paul Anderson discusses these topics in the
following video.
Plate Tectonics Explained (2:36)

“Plate Tectonics Explained.” YouTube. MinuteEarth, 13 Jan. 2015. Web. 27 Jan. 2015.
Are Earth’s plates giant conveyor belts just pushing the continents along? Find
out from this short video by MinuteEarth.
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General Science I A
Credit 2
Elaborate
Plate Boundaries
Plate tectonics is the study of how continents move and how features of Earth’s surface form. Large pieces of
Earth’s crust are called tectonic plates. Scientists have identified 15 major tectonic plates and many smaller
ones. As these tectonic plates move they carry the continents with them; therefore, the movement of these
tectonic plates explains the movement of the continents. Where one tectonic plate ends and another begins is
known as a plate boundary. An area where two tectonic plates are moving away from each other is called a
divergent boundary. An area where two tectonic plates are moving toward each other is called a convergent
boundary. An area where two tectonic plates are sliding past each other is called a transform fault boundary.
The table below summarizes these three types of plate boundaries. Use the table to answer the questions below.
Type of Boundary
Divergent Boundary
←→
Convergent Boundary
→←
Transform Fault Boundary
↓↑
Description
Plates moving away from each
other to form rifts and mid-ocean
ridges.
Plates moving toward each other
and colliding to form ocean
trenches, mountain ranges,
volcanoes, and island arcs.
Example
North American and Eurasian
plates at the Mid-Atlantic Ridge
South American and Nazca plates
at the Chilean trench along the
west coast of South America
North American and Pacific plates
Plates sliding past each other while
at the San Andreas Fault in
moving in opposite directions.
California
Adapted from Allison, Mead A., Arthur T. DeGaetano, and Jay M. Pasachoff. “Chapter 10 Section 2 Table 1: Plate Boundary Summary.” Holt McDougal Earth
Science. Austin, TX: Holt McDougal, a Division of Houghton Mifflin Harcourt, 2010. 271. Print.
1. Which plate boundary causes plates to collide forming mountain ranges, volcanoes, and island arcs?
Give an example of this type of plate boundary.
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
2. At which plate boundary do rifts and mid-ocean ridges form? Give an example of this type of plate
boundary.
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
3. At which plate boundary do plates slide past each other while moving in opposite directions? Give an
example of this type of boundary.
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
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Evaluate
Review Questions
Answer the following questions.
1. Why did many scientists reject Wegener’s hypothesis of continental drift?
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
2. What are some examples of evidence that support Wegener’s hypothesis of continental drift?
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
3. How are magnetic patterns in seafloor rock evidence of seafloor spreading?
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
4. Explain how seafloor spreading provides an explanation for how continents move across the surface of
the planet.
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
5. How do convection currents inside Earth’s mantle affect the movement of the plates that make up
Earth’s crust?
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
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General Science I A
Credit 2
LESSON 2.3: RESHAPING EARTH’S CRUST
Learning Goal for this Credit
Design an investigation or model using appropriate scientific tools, resources and methods.
Learning Goals for this Lesson
 Identify how movements of tectonic plates change Earth’s surface.
 Summarize how movements of tectonic plates have influenced climates and life on Earth.
 Describe the supercontinent cycle.
Lesson Assignments
 Connect to Prior Knowledge
 Exploration Activity
 Reading and Questions
 Videos (optional)
 Mapping Plate Boundaries
 Analysis Questions
Engage
Connect to Prior Knowledge
Do you think that the continents will eventually rejoin to form another supercontinent like Pangaea? Why or
why not?
_________________________________________________________________________________________
_________________________________________________________________________________________
_________________________________________________________________________________________
_________________________________________________________________________________________
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General Science I A
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Explore
Exploration Activity
The process of continental drift is constantly shaping and reshaping Earth’s crust. If you look at the current
continents, you will see they fit together like a jigsaw puzzle. Approximately 300 million years ago, the
continents formed the supercontinent Pangaea. Sometime in the far future the continents will rejoin to form a
supercontinent once again. This process is called the supercontinent cycle.
The plates that the continents rest on are constantly in motion. They move at a pace between 2-5 centimeters
per year (about the same speed as your fingernails grow). Using this information, answer the questions below.
Use the following conversions to help you with the problems below.
1 meter = 100 centimeters
1 kilometer = 100,000 centimeters
1 kilometer = 1000 meters
Example:
The United States is located on the North American plate. If the North American plate is moving at a speed
of 4 centimeters per year, how long would it take the plate to travel 10 meters?
Step 1: First we need to convert 10 meters to centimeters. From the conversions above, we know that there
are 100 centimeters in 1 meter.
𝟏𝟎𝟎 𝒄𝒎
𝟏𝟎 𝒎 𝒙
=?
𝟏𝒎
Step 2: Multiply across to obtain the answer. Notice how the units cancel when setup correctly.
𝟏𝟎 𝒎 𝒙
𝟏𝟎𝟎 𝒄𝒎
= 𝟏𝟎𝟎𝟎 𝒄𝒎
𝟏𝒎
Step 3: Now that we know how many centimeters the plate has traveled; we can use the conversion of “4
centimeters per year” given in the problem to convert from centimeters to years.
𝟏𝟎𝟎𝟎 𝒄𝒎 𝒙
𝟏 𝒚𝒆𝒂𝒓
=?
𝟒 𝒄𝒎
Step 4: Multiply across, and then simplify the fraction to obtain the answer. Once again, noticed how the
units cancel when setup correctly.
𝟏𝟎𝟎𝟎 𝒄𝒎 𝒙
𝟏 𝒚𝒆𝒂𝒓
𝟏𝟎𝟎𝟎 𝒚𝒆𝒂𝒓𝒔
=
= 𝟐𝟓𝟎 𝒚𝒆𝒂𝒓𝒔
𝟒 𝒄𝒎
𝟒
It would take approximately 250 years for the plate to travel 10 meters.
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1. If the North American plate is moving at a speed of 4 centimeters per year, how many meters will the
United States travel in 100 years?
2. In California, the Pacific plate slides past the North American plate. If the Pacific plate is moving at a
speed of 5 centimeters per year, how long will it take for the plate to travel 100 meters?
3. If the Pacific plate is moving at a speed of 5 centimeters per year, how many kilometers will the Pacific
plate travel in 1 million years?
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General Science I A
Credit 2
Explain
As you complete the reading, answer the questions in the space provided.
Reading
How Do Continents Change Shape?
Tectonic plates are always moving. The movements of the plates change Earth’s surface and affect its climate.
One of the ways plate movements affect Earth’s surface is by changing the shapes of the continents. The
continents have not always looked the way they look today. In the future, they will look different, too. There are
two main ways continents change: rifting and accretion. At a divergent boundary, tectonic plates move apart.
Today most divergent boundaries are under the oceans. However, divergent boundaries can also exist on
continents. For example, there is a divergent boundary in eastern Africa. At the East African Rift Valley, the
continent is breaking into pieces, or rifting. Rifting is the process in which a continent breaks apart. You can
also use the word rifting to describe what happens at a mid-ocean ridge.
Continents can also change shape by growing larger. A continent can grow larger if a volcano on it erupts.
Continents can also grow by accretion. In the process of accretion, new lithosphere is added to the edge of a
continent. The new lithosphere that is added is called a terrane. A terrane is a piece of lithosphere that has a
different geologic history from the lithosphere around it. Scientists have studied the geologic history of the
rocks on continents. They have learned that the centers of most continents are more than 540 million years old.
These very old, central parts of the continents are called cratons. The edges of the continents are made up of
different terranes. The terranes have formed over time at convergent boundaries. As one tectonic plate sinks
beneath another at a convergent boundary, terranes on the sinking plate are scraped off. They stick to the edge
of the continent on the other plate. Many different structures can make up terranes. Some terranes are
volcanoes that have erupted on the ocean floor. Other terranes are made up of coral or rock that forms along
beaches and on islands. Some terranes are made up of pieces of continental crust. A terrane may change a lot
when it is scraped off onto a continent. Scientists can identify terranes by looking for three features.



A terrane has different rocks and fossils than other terranes or cratons.
Large faults, or cracks in rock, divide a terrane from other terranes or cratons.
The rocks in a terrane generally have different magnetic properties than the rocks in other terranes.
1. The oldest rocks on Earth are found on the continents. Are these rocks most likely found in the centers
of continents or at their edges? Explain your answer.
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
2. What occurs during rifting?
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
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How Do Continental Movements Affect Earth?
The movements of the plates do not affect only the shapes of the continents. As the plates move, the continents
also move. Mountains form and are broken down. Continents move closer to or farther from the equator. These
changes and movements can affect Earth’s climate. They can also affect life on Earth.
The movements of ocean water affect Earth’s climate. Cool ocean water that flows near a continent can make
the continent cooler. Warm water flowing near a continent can make the continent warmer. The positions of the
continents affect the movement of ocean water. The movement of ocean water affects climate. Therefore, as the
continents move, climate can change.
When a continent breaks apart or a mountain forms, groups of living things can be separated. For example, one
group of mice might be split into two groups. The two groups will live in different environments. Over time,
they may evolve, or change, into new types of living things. In this way, plate tectonics can affect life.
3. How can the movements of the continents affect Earth’s climate?
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
How Have the Continents Changed Over Time?
Alfred Wegener thought that all the continents had
once been joined into a single supercontinent.
Scientists have found evidence that he was correct.
However, scientists today think that there may have
been more than one supercontinent. They think the
continents have joined and broken apart many times
over Earth’s history. The process in which the
continents come together, form a supercontinent, and
then break apart again is called
the supercontinent cycle. Right now, the continents
are broken apart. Over millions of years, the continents
will move together and form another supercontinent.
The most recent supercontinent was called Pangaea.
Pangaea formed about 300 million years ago, when the
continents moved together. As the continents collided,
mountains formed. The Appalachian Mountains in
North America formed at this time. A large ocean
called Panthalassa surrounded Pangaea.
About 200 million years ago, Pangaea began to break
apart. At first, a large rift split Pangaea into two pieces.
Scientists call the pieces Laurasia and Gondwanaland.
Over time, Laurasia and Gondwanaland also began to
break apart. Laurasia broke into pieces that became
North America, Europe, and Asia. Gondwanaland
broke into pieces that became South America, Africa,
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India, Australia, and Antarctica. About 50 million years ago, India collided with Asia. The Himalaya
Mountains began to form. India and Asia are still moving together today. Thus, the Himalaya Mountains are
still growing.
Scientists can use information about how the plates are moving to predict what Earth will look like in the future.
They think that in about 250 million years, the continents will form a new supercontinent. Africa will collide
with Europe and Asia. North America and South America will collide with Africa. Australia and Antarctica will
come together. The process in which the continents come together, form a supercontinent, and then break apart
again is called the supercontinent cycle. Right now, the continents are broken apart. Over millions of years, the
continents will move together and form another supercontinent.
4. Describe the difference between Pangaea and Panthalassa.
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
5. Describe how convergent and divergent boundaries are related to the supercontinent cycle.
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
Allison, Mead A., et al. “Chapter 10: Plate Tectonics/Section 3: The Changing Continents/Transparency 53 The Supercontinent Cycle.” Holt McDougal Earth Science, Holt McDougal, a
Division of Houghton Mifflin Harcourt Publishing Co., 2010.
Allison, Mead A., et al. “Chapter 10: Plate Tectonics/Section 3: The Changing Continents.” Holt McDougal Earth Science Interactive Reader, Holt McDougal, a
Division of Houghton Mifflin Harcourt Publishing Co., 2010, pp. 155-160.
Videos
If you would like to learn more about this topic, watch the videos below for more information. (Optional)
Continental Drift 101 (1:21)

How did the supercontinent Pangaea break apart to form the continents
we know today? This video will explain how continents are constantly on the
move.
“Continental Drift 101 | National Geographic.” YouTube. National Geographic, 3 Nov. 2016. Web. 26 Apr. 2021.
Plate Tectonics (4:12)

What processes occur at different plate boundaries? In this interactive
virtual investigation, you will explore different plate boundaries and investigate
the plate boundaries of an alien planet.
“BBC Geography – Plate Tectonics.” YouTube. Evans Woolfe Media, 11 Sep. 2017. Web. 26 Apr. 2021.
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Elaborate
Mapping Plate Boundaries
Background:
Before the 1920’s, common thinking was the Earth was a solid, stable ball of rock. Then, a German scientist
named Alfred Wegener proposed the Theory of Continental Drift, suggesting that the Earth’s crust was not one
solid mass but several large, moving landmasses. Although his ideas were not widely accepted during his life,
his theory is now the basis for the study of plate tectonics. The theory states the Earth is a collection of many
moving slabs of rock all of which are interacting dynamically (constantly changing).
Scientists believe the lithosphere is broken up into more than a dozen slabs or plates which move in various
directions. A plate boundary is where plates adjoin or touch each other. When plates move toward each other,
their boundaries are convergent boundaries. When plates move away from the other they are divergent
boundaries. When plates move alongside or parallel to each other they are transform boundaries. Plate
movement is responsible for every change on the surface of the earth. The creation of mountains, volcanoes,
earthquakes, and other geological processes which occur on earth are related to the movement of these plates.
Complete the following activity using the map on the next page.
Materials:


Colored pencils, crayons, or nontoxic colored markers
Map on next page
Procedure:
1.
2.
3.
4.
5.
Find the map on the next page titled tectonic plates.
Choose a color for convergent boundaries.
Color all of the convergent boundaries that color including the key at the bottom of the map.
Choose a different color for the divergent boundaries and color those including the key.
Choose a third color for the transform boundaries and color those including the key.
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Evaluate
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Analysis Questions
Answer the following questions using the map on the previous page.
1. Find the mid-Atlantic ridge on the map. What kind of plate boundary is found here?
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
2. Find the San Andreas fault on the map. What kind of plate boundary is found here?
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
3. Find the Aleutian trench on the map. What kind of plate boundary is found here?
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
4. Find the East African rift on the map. Explain what is occurring here.
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
Revisit the essential question, did your answer change? Why or why not?
Essential Question
Do you think mankind will ever reach the center of the Earth? Why or why not?
__________________________________________________________________________________________
__________________________________________________________________________________________
__________________________________________________________________________________________
__________________________________________________________________________________________
Performance Task
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Lesson
2.1
Title
Earth’s Structure
2.2
Continental Drift and
Plate Tectonics
2.3
Reshaping Earth’s
Crust
Learning Goals For Each Lesson

Describe the size and shape of Earth.

Describe the compositional and structural layers of Earth’s interior.

Identify the possible source of Earth’s magnetic field.

Summarize Newton’s law of gravitation.

Summarize evidence for the hypothesis of continental drift.

Describe the process of sea-floor spreading.

Explain how sea-floor spreading provides a mechanism for continental drift.

Summarize the theory of plate tectonics.

Identify and describe the three types of plate boundaries.

Identify and describe three causes of plate movement.

Identify how movements of tectonic plates change Earth’s surface.

Summarize how movements of tectonic plates have influenced climates and life on Earth.

Describe the supercontinent cycle.
General Science Rubric
Credit Grading
Responses to Packet
and Questions
40 pts.
Performance Task
40 pts.
Quiz
20 pts.
4
 My responses in
my packet show
clear reasoning and
use of evidence.
3
 My responses in
my packet show
basic reasoning and
use of evidence.
2
 My responses in
my packet show
basic reasoning but
limited evidence to
support it.
1
 My answers to the
questions in my
packet are either
unscientific or
overly simplistic,
and have limited
evidence.
 I completed some
of the expectations
of the assignment
to show what I
know.
 I completed some
of the expectations
but struggled to
show what I know.
 I made connections
to other ideas
within and across
science credits.
 I completed all of
the expectations of
the assignment to
thoroughly show
what I know.
 My explanation is
clear and supported
by valid scientific
evidence.
 I mainly completed
the expectations of
the assignment to
show what I know.
 My explanation is
supported by
scientific evidence.
 My explanation is
simplistic or basic
and supported by
limited scientific
evidence.
 My explanation is
not supported by
scientific evidence.
Students receive 2 points per correct response.
___x 10 = ___/40
___x 10 = ___/40
___x2 = ___/20
Total:
___/100
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General Science I A
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