Download Earth Science for Struggling Students Book 1: Inside the Earth

Earth Science for Struggling Students
Book 1: Inside the Earth /Earth’s Interior
Chapter 1: Layers of the Earth
Vocabulary Building:
1direct
.
evidence
Evidence that has been directly observed with the five senses, and that requires no
assumptions or inferences to be drawn. For example, using rock samples or soil sample
to analyze.
indirect evidence
A set of clues that scientists use to make guesses about things they cannot see or test
directly.
Crust
the thin and solid outermost layer of earth above the mantle
Mantle
a thick layer of hot but solid rock
lithosphere
a rigid layer made up of the uppermost part of the mantle and the crust
asthenosphere
the soft layer of the mantle on which the lithosphere floats
.
convection currents
Circular currents in the mantle caused by the magma being heated by the core off the
Earth.
Core
Inner zone of the earth. It consists of a solid inner core and a liquid outer core.
composition
The chemical makeup of a rock; describes either the minerals or other materials in the
rock
3
.
Density
the amount of matter in a given space; mass per unit volume
5
.
6seismic
.
waves
waves produced by earthquakes that help us study the inner layers of Earth
9
.
Jack Meadows was not your typical 12 year old boy. He was quite fascinated by space
and everything that revolves around it. To him, Earth is a mystical place, full of mysteries that
he was determined to solve. Jack will start 6th grade in just a few days. His cousin, Melody
Lambert, a rising seventh grader warned about the sixth grade science curriculum. She
explained that the first topic he will be learning about was Earth’s interior.
Jack wondered, “How could a person actually get inside the Earth to learn about its
composition?” Jack grabbed his Apple i-Pad Air tablet to start his search about the Earth’s
interior. In his search, Jack learned that geologists relied on two main types of evidence to look
inside the Earth: Direct and indirect evidence. Jack was further confused. “What exactly is
direct and indirect evidence?” he thought.
Jack put down his tablet, and ran in search of his dad. Dr. Jeremy Meadow was the
research director for a major geological site at the University of Georgia. “Dad, what exactly is
direct and indirect evidence used by geologists?” Dr. Meadow pondered the question. “What
exactly are the geologists looking at?” “Well, I was trying to find out what the inside of the Earth
would look like,” said Jack. “Geologists, like me, use rock samples and soil samples. These
are examples of direct evidence. They also use seismic waves from earthquakes to learn about
Earth’s interior. Direct evidence gives clues to the composition and structure of the rocks that
make up Earth. Indirect evidence, such as seismic waves, is given off during Earthquakes. The
speed and paths these waves travel help to describe the structure of the Earth. “Wow, thanks
dad.” Jack realized that there was more to discover about the Earth’s structure.
Jack decided to return to his tablet to research what layers were found inside the Earth.
In his search, he found that the Earth had four layers, much like an onion or a hard-boiled egg.
The first layer starting from the outside moving inwards was called the crust, followed by the
mantle, and the outer and inner core. The crust was solid rock, and it is the place where we
live. The mantle is made up of three parts: The lithosphere, the upper most part of the
mantle, is also part of the crust. The middle mantle, called the asthenosphere, is semi-solid
and can bend like hot plastic. In this region you can find the convection currents. Here heat
is distributed. The heat near the core rises towards the lithosphere, while the relatively colder
air flows back down to the core where it is reheated again. The movement of cold liquid and hot
liquid from the lithosphere to the lower mantle is called convection currents. It is believed that
the lithospheric plates or tectonic plates rest on the lithosphere and these convection currents
generate enough movement to cause the plates and continents to move. The last part of the
mantle is the lower mantle. This part of the mantle is solid and very hot because it lies next to
the core. The core has two parts: The outer core is molten or liquid iron and nickel. The
second part of the core is the inner core. The inner core is dense and solid iron and nickel. It
is solid because it is at the highest pressure. Temperature, pressure, and density increase
as you move from the crust towards the inner core. Since the liquid outer core is made
of iron, movement within this layer creates Earth’s Magnetic field.
Figure 1

Figure 2
Jack was amaze at the depth and structure of the Earth and the amount of information that
geologists were able to uncover using direct and indirect evidence.
Jack summarized the information as follows: Scientists use direct evidence to study the
interior of the Earth. Direct evidence is evidence that can be touched and analyzed. Indirect
evidence cannot be touched and is based on assumptions or inferences.
Discussion questions:
1.
Write a brief summary of Jack’s discovery of the Earth’s structure.
2. Differentiate between the lithosphere/asthenosphere and the outer core /inner core.
3. Describe what convection currents are and how they form in the mantle.
Extension: (Analysis)
1. What do you think would happen to the convection currents in the mantle if Earth’s
interior cooled down?
Chapter 2: Continental Drift and Pangaea
Vocabulary Building:
fossil
Preserved remains of once-living organisms
continental drift
The hypothesis that the continents slowly move across Earth's surface.
Pangaea
According to geologists, the earth originally had only one "supercontinent"
that drifted apart, subsequently into the 7 continents.
PBS, Public Broadcasting Station, was broadcasting a documentary on the theory of
continental drift. As Jack watched the broadcast, he learned that continents were once joined
together like pieces of a puzzle. It once existed as a single land mass called Pangaea. The
continents have since drifted apart. Putting together puzzle pieces was one of Jack’s strengths.
He has been putting together puzzle since he was a preschooler. Jack pondered how this was
possible. A whole new adventure was opened up to Jack. Jack was determined to get the
answers he needed.
After watching the broadcast, Jack seemed to have more questions than answers. He
decided to call his cousin, Melody Lambert. “Hey Melody, can you tell me what you know about
the hypothesis of continental drift?” ”Well according to Mrs. Stark, a scientist by the name of
Alfred Wegener hypothesized that all seven continents were once joined together in a
supercontinent called Pangaea. However, Wegener was unable to explain the phenomenon
that caused the continents to drift apart.” “But what evidence did Wegener used that led him to
believe that the continents were once connected or joined?” asked Jack. “You may need to do
some further research to find out,” answered Melody. “Thanks,” replied Jack.
Jack grabbed his tablet and preceded to Google the hypothesis of continental drift and
Albert Wegener. Jack discovered that Wegener found evidence from land features, evidence
from fossils, and evidence from climate. “Wow, this was interesting stuff,” thought Jack. “What
could these evidence be?” pondered Jack. In his research, Jack read that Wegener pieced
together the maps of Africa and South America. He saw that the mountain ranges on the east
of South America fit completely with the West coast of Africa. This provided the evidence of
land features. Wegener found samples of the fossil Lystrosaurus and Mesosaurus in places
that were separated by oceans. Neither reptile could swim, so the land had to have been once
joined together. A fern-like plant called Glossopteris was found in the rocks of several
continents. When Wegener studied the continent of South Africa, he observed that South Africa
had once been covered with continental glaciers. This showed that South Africa was at one
time very close to the South Pole. This provided the evidence of climate. Jack put down his
tablet, and rushed to find his father.
Figure 1
Figure 3
Figure 5
Figure 2
Glossopteris
Pangaea
Figure 4 Alfred Wegener
Map of the Pangaea
“Dad, why was it so difficult for the people to accept Wegener’s hypothesis of continental
drift?” pressed Jack. “Alfred Wegener was unable to provide a satisfactory explanation of the
types of forces that were needed to push or pull the continents.
Jack summarized the facts that he was able to gather as follows: The world was joined
together as a super continent called Pangaea. Over time the continents slowly drifted apart. He
found evidence from land features, evidence from fossils, and evidence from climate. Scientists
were reluctant to accept Wegener’s hypothesis of continental drift, because he was unable to
provide a satisfactory explanation of the forces that caused the continents to pull apart.
Discussion questions:
Explain Alfred’s hypothesis of continental drift.
1.
2. What evidence did Alfred’s Wegener use to hypothesize that a supercontinent once
existed?
3. According to the hypothesis of continental drift, how would a map have changed over the
last 250 million years?
Extension: (Synthesis)
1. Using a map of the continents cut out each continent and arrange them to show what
you think the world would look like 200 million years from now. Color, cut then glue.
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Chapter 3: Mid-Ocean Ridges and Sea-Floor Spreading
Vocabulary Building:
Mid- ocean ridge
An under ocean mountain chain where new ocean floor is
produced at a divergent plate boundary.
Sonar
A device that determines the distance of an object under
water by recording echoes of sound waves
Sea-floor spreading
A hypothesis that new sea floor is created at mid-ocean
ridges and that in the process the continents are pushed
apart from each other.
Basalt
A dark, dense, igneous rock with a fine texture, found in
oceanic crust.
Trench
A deep valley under the ocean where oceanic crust is
pulled back into the mantle by sub-duction.
Sub-duction
The process by which oceanic crust sinks beneath a deepocean trench and back into the mantle at a convergent
plate boundary.
Jack remembered reading about the strangest features and bizarre creatures
that live in the oceans. His dad told him that the features on the ocean floor provided the
best evidence of continental drift. Jack wanted to learn more about the events that
caused the continents to drift apart. Jack got his tablet and Google evidence of
continental drift.
According to the search, in each of the five major oceans; Pacific, Atlantic,
Indian, Arctic, and Southern Oceans, there is a mountain chain. This mountain range is
called the Mid-Ocean Ridge. The Mid=Ocean Ridge snakes down the entire length of
each of the major oceans of the world. This feature is one key feature that can explain
the phenomenon that caused the continents to drift apart.
Jack continued his search to include the scientist who inadvertently discovered
the evidence that eluded Alfred Wegener decades earlier. This scientist was Harry
Hess. Hess used a device called sonar, to study the mid-ocean ridge. Hess proposed
a phenomenon called Sea-Floor Spreading, to explain why the continents drifted apart.
Sea-Floor Spreading causes the ocean floor to be pulled apart from both sides of the
mid-ocean ridge, or mountain ranges. This happens at divergent plate boundaries found
at the rift. The ocean floor is being pulled apart like conveyor belts carrying the
continents with them. At the rift, on either side of the mid-ocean ridge, a volcano is
present. The rift is like an opening or crack at the Mid-Ocean Ridge. The lava hardens
as it erupts onto the surface of the ocean floor. As the lava hardens it adds new rock
material or crust, to the ocean floor. The most common oceanic crust is basalt, a type
of extrusive igneous rock.
Jack left his bedroom and went to his dad’s study. He knew his dad had several
biographies and periodical about Harry Hess’s work. He pulled one of the periodicals
from his dad’s library shelves. He scanned the Table of Contents until he found what he
was looking for, “Evidence to support continental drift,” Jack whispered. Jack began to
read. According to Harry Hess, the evidence that supported Sea-Floor Spreading came
from three sources: 1) Evidence from Molten Material or lava cooling rapidly from
erupting volcanoes. 2) Evidence from magnetic strips. As you learned earlier, the solid
inner core of Earth contains iron. This created a magnetic field around the Earth.
Scientists discovered that the rocks that make up the oceanic crust lies in a series of
magnetized strips. When the scientists studied these magnetized strips, the discovered
that the strips contained a record of all the Earth’s magnetic reversals. The rocks
contained iron that aligned with the Earth’s magnetic field. This sealed the iron bits in
the rocks in place giving the rock a sort of magnetic “memory”. 3) Evidence from drilling
samples. When Hess brought up drilling samples of rocks taken from various sections
of the ocean floor, he discovered that the newest rocks were found near the Mid-Ocean
Ridge and the oldest rocks were found further away from the Mid-Ocean Ridges, at the
deep ocean trenches.
“What is an ocean trench,” Jack whispered to himself. Putting down the
periodical, Jack decided to look into the encyclopedia. He read that ocean trenches are
deep valleys miles deep under the ocean. At these deep ocean trenches, oceanic crust
is pulled by gravity back into the mantle to be re-melted back into magma. The process
by which the oceanic crust is pulled back into the mantle is called sub-duction.
Jack summarized that continental drift occurred as a result of sea-floor
spreading, subduction, and convection currents in the asthenosphere of the mantle.
Discussion questions:
1. Explain the processes that caused the continents to drift apart.
2. Explain what three types of evidence provided support for the theory of sea-floor
spreading?
3. How do rocks along the mid-ocean ridge and trenches provide evidence of sea=floor
spreading?
Extension: (Synthesis)
1.
What happens to oceanic crust at a deep ocean trench? Explain.
Chapter 4: Exploring the Ocean Floor
Vocabulary Building:
Continental shelf
A gently sloping, shallow area of the ocean floor
that extends outward from the edge of a continent.
Continental slope
A steep incline leading down from the edge of the
continental shelf.
Continental margin
The shallow sea floor that is located between the
shoreline and the deep-ocean bottom.
Continental rise
The gently sloping area at the base of the
continental slope.
Guyot
Flat-topped seamount
Seamount
A mountain on the ocean floor that is completely
underwater
Abyssal plain
the vast floor of the deep oceans
Marianas Trench
The deepest part of the world's oceans located in
the Western Pacific. This is the location where the
Pacific plate sub-ducts causing a trench.
Island arc
A string of islands formed by the volcanoes
along a deep-ocean trench.
The depths of the ocean remain largely unexplored. There are many creatures
that remain to be discovered. Hollywood has been making many intriguing movies with
monsters and other sea creatures. One of Jack’s favorite movies to watch is The
Abyss. This epic film was taped underwater near the deepest ocean trench, the
Mariana’s Trench. This movie piqued the interest of Jack. Jack knows that he will be
learning about the different features of the ocean floor. In the movie, Jack wanted to
study the ocean floor so that he could learn about all those features that he saw in the
Abyss.
Jack went for his tablet, and began to Google features of the ocean floor. Here
are some interesting features that he discovered.
Jack read about the continents
divided the major oceans. The continental shelf is a landmass that extends from a
continent that is covered by water. This is similar to stepping from the beach into the
ocean. It is an area of very shallow water. The continental slope is the steep incline of
the continent, between the continental shelf and the abyssal plain. It is considered the
sides of the continents as it dips steeply to the ocean floor. The continental margin
includes the continental shelf, the continental slope, and the abyssal plain. The abyssal
plain is the nearly flat ocean floor covered by thick layers of mud, silt, and dead plants
and animal remains. Along the abyssal plain are guyots. Guyots are underwater
volcanoes that have been flattened by weathering and erosion caused by deep ocean
currents or waves. Guyots are completely submerged underwater. Seamounts are
volcanoes that are completely submerged underwater. They look like volcanoes.
Winding along the length of each major ocean is a mountain range called Mid-ocean
Ridge. A rift is an opening on either side of the Mid-ocean Ridge. Volcanoes spew lava
to the surface of the abyssal plain. Further along the abyssal plain is a deep canyon
called a trench. The Marianas Trench is the deepest part of the oceans of the world.
It is located in the western Pacific Ocean, off the Coast of Japan. It is about 2,550
kilometers deep. It is at the trenches that the oldest rocks are subducted back into the
mantle. Volcanoes are found here. Volcanoes erupt over a hotspot in the Earth’s
mantle, creating a chain of island called an island arc. The most famous islands are the
Hawaiian Islands in the Pacific Ocean.
Figure 1
Figure 2
Figure 4
Figure 5
Guyot
Figure 3 Seamount
Volcanic Island
Marianas Trench
Jack summarized his findings. The ocean floor is similar to some of the features
found on the continents. The features on the ocean floor, however, are longer, wider,
taller, and deeper than those on the continents. Features found on the ocean floor
include continental shelf, continental slope, abyssal plain or ocean floor, guyots,
seamounts, island arcs, mid-ocean ridges, and ocean trenches.
Discussion questions:
1. Imagine you are travelling along the ocean floor in a submersible vessel. Write about and
describe all the features that you may see on your journey.
2. How does the ocean floor compare to the continents? What features are similar and what
features are different?
Extension: (Synthesis)
1. Sketch an outline of the ocean floor. Make sure to include, continental shelf, continental
slope, abyssal plain, guyot, seamount, island arc, mid-ocean ridge, trench. Also include the
label for each feature.
Chapter 5
Plate Tectonics
Vocabulary Building
Lithospheric plate
A section of earth's lithosphere that carries
continents.
Theory of plate tectonics
State that Earth's lithosphere is broken into huge,
moving slabs of rock driven by motions in the
mantle.
Plate boundaries
Breaks between plates.
Divergent plate boundaries
where two plates are moving apart, magma comes
up to create new crust.
Convergent plate boundaries
A plate boundary where two plates collide with
each other, forming mountains, trenches,
earthquakes, and volcanoes.
Transform plate boundaries
Area where two tectonic plates meet and slip and
grind alongside one another, creating earthquakes.
For example, the Pacific Plate and the North
American Plate rub against each other along
California's San Andreas Fault.
Rift valley
A deep valley that forms where two plates move
apart.
Ring of Fire
Area around the Pacific Ocean known for frequent
earthquakes and volcanoes.
Tsunami
A giant wave caused by an earthquake on the
ocean floor.
Focus
Point at the depth where the rocks ruptured to
produce earthquakes; place where quake waves
originate.
Epicenter
Point on Earth's surface
earthquake's focus.
Seismic waves
A vibration that travels through Earth carrying the
energy released during an earthquake.
directly
above
an
At breakfast, Jack held a hard-boiled egg in his hand. Jack noticed that the egg
shell had cracks in irregular patterns. Jack’s dad noticed his serious and careful
examination of his egg. “Jack, did you know that a hard-boiled egg is often compared to
the cracks on Earth’s ocean floor, cracks on the continents, and cracks in the Earth’s
lithosphere?”
“Really dad! Why is that?” asked Jack.” Jack, the lithosphere, which is the upper
layer of the mantle that is also attached to the crust, has many separate sections called
lithospheric or tectonic plates. The plates carry the continents, or parts of the ocean
floor, or both. These plates move because of the convection currents in the
asthenosphere in the middle mantle, sea-floor spreading, and continental drift.” “The
theory of how these tectonic or lithospheric plates form, how they move, and how they
sud-duct is called the theory of Plate Tectonics,” continued dad. “Well I have to hurry
with my breakfast so I can research the theory of plate tectonics,” replied Jack. Jack
hurried to his room, and grabbed his tablet. Jack Google: The Theory of Plate
Tectonics.
During his research, Jack read about how the tectonic plates moved. As these
tectonic or lithospheric plates move, they collide, pull apart, or grind past each other at
plate boundaries. There are there three types of plate boundaries.
1. Divergent plate boundary: Tectonic or lithospheric plates move apart. A) In the
ocean, divergent plates are found at the mid-ocean ridges, where sea-floor
spreading occurs.
B) On land, where two lithospheric plates or tectonics plates diverge or pull apart, a rift
valley forms. The Great Rift Valley in East Africa is one example.
2. Convergent Plate Boundary: When two lithospheric plates or tectonic plates come
together or converge. This is also known as a collision. There are three types of
convergent plate boundaries. A) When two oceanic plates collide, sub-duction
occurs at the trenches. Islands are formed. Most famous islands are Hawaii and
Iceland.
3. B) When an oceanic crust and continental crust collide, sub-duction takes place.
The denser oceanic crust sub-ducts under the less dense continental crust.
Volcanoes, trenches, and islands are formed.
C) When two continents collide, both crusts are of equal density, do sub-duction does
not take place. Instead the continental crusts folds up to form huge mountain ranges.
Some examples are the Himalayan Mountains, Alps, Rockies, and Appalachian
mountains.
4. When two lithospheric plates or tectonic plates slide past each in opposite directions,
a transform plate boundary is formed. Earthquakes are formed at this type of plate
boundary. Crust is neither created nor destroyed at transformed plate boundaries.
The San Andreas Fault is a transformed plate boundary.
The Ring of Fire found in the Pacific Ocean, is proned to many earthquakes and
volcanoes.
Jack now has a deeper understanding of the forces inside the Earth that produces
earthquakes and volcanoes. Jack wanted to learn more about what earthquakes are and the
way earthquakes travel inside the Earth’s crust.
Jack decided to use his dad’s reference book to find the answers to his questions. Jack
read that earthquake is the shaking and trembling caused by the movement of rocks beneath
Earth’s surface. Plate movements cause stress along cracks or faults near these plate
boundaries. When the rocks break, at the faults, an earthquake is formed. If an earthquake is
formed under the ocean, a tsunami or tidal wave is formed. The focus of an earthquake is the
area beneath Earth’s surface where rock breaks. The epicenter is the point on the surface
directly above the focus.
Jack further learned that there are three types of seismic waves. Seismic waves carry
the energy from the focus, through the Interior of the Earth and its surface. The P wave is the
first wave to arrive. P stands or primary wave. It compresses and expands like an accordion.
P waves can damage buildings. P waves can travel through solids and liquids. The S waves or
secondary waves come after the primary waves. These S waves vibrate from side to side or
up and down. They cause the ground to move back and forth, shaking buildings violently. S
waves cannot move through liquids only solids. Surface waves are formed when P and S
waves come to the surface. Surface waves move slower than P or S waves. Surface waves
make the ground roll like waves on an ocean.
Jack summaries his findings. There are three main types of plate boundaries.
Divergent plate boundaries occur when crusts pull away from each other. Divergent plate
boundaries are formed at mid-ocean rides and at rift valleys. Convergent plate boundaries
occur when two plates come together or converge. When an oceanic and an oceanic crust
collide or an oceanic – continental crust collide, sub-duction takes place at the trenches. Crust
is destroyed, volcanoes are found, and islands are formed. Earthquakes are caused by the
buildup of stress or energy on a weakened section of rocks inside the Earth. When a rock
breaks at a fault, the trembling felt is an earthquake. The energy is carried away from the focus
or point at which the earthquake starts. It is carried by the P waves, S waves, or the surface
waves.
Discussion questions:
1. In your own words, what is the theory of plate tectonics?
2. Differentiate between the three types of convergent plate boundaries. State the different
features found at each type of plate boundaries.
3. Differentiate between a transform plate boundary and a transformed plate boundary. State
the types of features formed at each type of plate boundaries.
4. What is the Ring of Fire, and where can it be found? What features do you expect to find
around the Ring of Fire?
Extension: (Synthesis)
1. Sketch the three types of plate boundaries. Label each type, and name the features formed
at each type of plate boundaries.