Download what`s inside the earth?

WHAT'S INSIDE THE
EARTH?
An Introduction to the Earth's Interior,
Crust and Mineral Resources
1 videocassette . . . . . . . . . . . . . . . 26 minutes
Copyright MCMXCV
Rainbow Educational Media
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Raleigh, NC 27616-3177
Distributed by:
United Learning
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Evanston, IL. 60201
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PRINCIPAL CREDITS
Producer, Writer and Director: Peter Matuiavich
Jim Mod, Ph.D. Scientist
Consultants:
in Charge United States
Geological Survey
Mike Worosz, M.A.
Curriculum Consultant
Videography & Animation:
Associate Producer:
Production Manager:
Special Thanks to:
Peter Matuiavich
Diann Fried
Roxanne Hall
United States
Geological Survey
Kennecott Corporation
Pacific Gas & Electric
National Geophysical
Data Center Yellowstone
National
Park
Yosemite National Park
Grand Teton National
Park
Glacier National Park
Waterton Lakes National
Park Tropical Vision
Video
Video and teacher's guide produced for
Rainbow Educational Media
by Peter Matuiavich Productions
San Dimas, California
TABLE OF CONTENTS
Introduction
1
Objectives
2
Summary
3
Review Questions
6
Discussion Questions
10
Activities
13
Glossary
15
Bibliography
18
Script
21
INTRODUCTION
This video is designed to be an introductory guide to the earth's
interior, crust and mineral resources. It is intended to prepare
students for more advanced topics in earth science.
Students will learn through exciting, full-motion animation that
the earth's interior consists of layers and the outermost layer is
broken into pieces called plates. The plates are moving at a
rate of an inch or two a year, in a variety of directions, driven
by the movement of magma within the earth's mantle. Plate
movement is responsible for mountain building, volcanic
eruptions, and the occurrence of earthquakes. The video
clearly explains each of these geologic phenomena and
classroom demonstrations help bring these complex processes
into simpler terms for children to grasp more easily.
The video goes on to explain the three rock types: igneous,
metamorphic and sedimentary, and how each is formed.
Students will see how water finds its way into the earth's crust,
and how in some places it becomes heated and erupts in the
form of geysers. Sometimes the steam produced by geysers
and hot springs can be used to produce energy. Geothermal
energy is just one form of energy taken from the earth. Other
energy sources include oil, gas and coal.
In addition to energy, the earth's crust provides us with
precious gems, minerals and metals.
OBJECTIVES
After viewing this video, students should know:
• how scientists determine what's inside the earth
• the names of the earth's interior layers
• that the earth's plates are moving
• the importance of faults and how they relate to
earthquakes
• the nature of seismic waves
• how fault-block and folded mountains are made
• where lava originates
• how magma chambers are formed
• how lava erupts from volcanoes
• the three rock types and how they are formed
• how geysers and hot springs occur
• how oil, gas and coal are formed
• some of the earth's important mineral resources
SUMMARY
The video opens with dramatic scenes of volcanic eruptions
on the Island of Hawaii, Old Faithful erupting in Yellowstone
Park, and oil being pumped from the ground. The narrator
makes the point: "Oil, water, lava: these are just a few of the
things that come from deep within the earth."
Next, we see students examining a large globe. As useful as
globes are, they are unable to tell us what's inside our planet.
Since nobody has ever been to the center of the earth, how do
we know what's there? Students will learn that scientists set
off explosions on the surface and then analyze how the
resultant shock waves travel through the earth. Shock waves
travel differently through different materials, and this is
essentially how scientists are able to determine what makes
up the earth's interior.
Full-motion animation then reveals the various layers of the
earth's interior: the inner core, the outer core, the mantle, and
the outer shell which is composed of the crust and upper
portion of the mantle.
Students learn that the earth's shell is cracked into more than a
dozen pieces, called plates, and that each plate carries a
continent, or an ocean basin, or both. The positions of these
plates are only temporary. The plates are moving at an
average rate of one to four inches a year in a variety of
directions. The movement of the plates and the grinding that
occurs near their edges has been going on for so long that
each plate is riddled with cracks.
Most of the cracks are located deep within the ground, but in
some places, sections of crust have been uplifted and you can
actually see the cracks. Some of the cracks are called faults,
and sometimes a fault will slip or move apart, releasing a
great deal of energy in the form of seismic waves. The
shaking caused by the seismic waves is called
an earthquake. Students learn that there are thousands of
earthquakes each year and some of them can cause considerable
destruction.
Animation then reveals how surface faults can cause one
section of crust to rise miles into the sky, creating fault-block
mountains.
Students featured in the video conduct a classroom
demonstration where they bend and snap sticks, mimicking the
snapping of a fault and the creation of fault-block mountains.
They also squeeze towels together, mimicking the creation of
another type of mountains: folded mountains. Dramatic
footage features fault-block and folded mountains.
The video abruptly segues to awesome shots showing lava
erupting from Hawaiian volcanoes. Students learn the lava
comes from deep within the earth, finding its way to the
surface through the crust and then erupting on the surface.
Featured in this exciting sequence are lava fountains, lava
curtains, and lava flows. Some of the lava reaches the sea,
where it cools, hardens into rock, and forms new shorelines.
Sometimes magma rises from the mantle and never reaches the
surface; and animation shows how magma deposits, called
magma chambers, can exist just below the surface. When it
cools, the magma hardens into rock known as igneous rock,
one of the earth's important rock types. Metamorphic rock is
another rock type created by the process of heat.
Just as magma finds its way up through cracks in the earth's
crust, water finds its way down into the crust. Students will
learn that water can be absorbed by rock just as it can be
absorbed by a sponge; and students conduct a classroom
demonstration where water is shown being absorbed by
sandstone.
Animation then shows how water can fill underground
chambers and sometimes these chambers occur near magma
chambers. The water becomes heated by the magma and
boils, building up pressure, causing surface eruption, referred
to as a geyser. Water and magma chambers exist under
Yellowstone National Park and that's why the area is known
for its many geysers and hot springs. Power plants have been
built in other geothermal areas and they have been able to use
the steam produced by hot springs and geysers to generate
electricity.
Students learn that people have been using the things they find
in the earth to make energy, for a long time. Other energy
finds include oil, gas, and coal, and the video discusses how
they can form under layers of sedimentary rock.
The video concludes with a discussion on how we obtain
minerals and metals from the earth's crust.
REVIEW QUESTIONS
1. How have scientists determined what's
inside the earth?
Scientist are able to determine what's inside the earth by
analyzing shock waves as they travel through the earth.
2. What are the earth's interior layers?
The interior layers are called the inner core, the outer
core, the mantle and the outer shell.
3. The outer shell is broken into more than a
dozen moving pieces. What are these pieces
called?
The moving pieces are called plates.
4. What are faults?
Faults are cracks in the earth's crust.
5. What causes earthquakes?
Earthquakes are caused by sudden movement along a
fault.
6. How is energy released during an
earthquake?
Energy is released in the form of seismic waves.
7. Seismic waves are similar to what type of
commonly seen waves?
Seismic waves are similar to the waves created when a
stone is tossed into a pond.
8. Uplifted sections of the earth's crust create
what?
Fault-block mountains are created by the uplifted
sections of the earth's crust.
9. What type of mountain is formed when the
earth's crust is squeezed together?
Folded mountains are made when the earth's crust is
squeezed together.
10. What is the hot liquid that erupts from
volcanoes?
It is called lava.
11. What is magma?
Magma is the name for lava before it reaches the
earth's surface.
12. What is a lava fountain?
It is lava that erupts like a fountain, shooting high into
the air.
13. What is a lava curtain?
It is lava that erupts through a large crack in the
earth's surface, in the form of a curtain.
14. Of what material are the Hawaiian Islands
made.
The Hawaiian Islands are formed from lava which has
hardened into rock.
15. What are large underground lava deposits
called?
Underground lava deposits are called magma
chambers.
16. What type of rock is formed when a magma
chamber cools?
Igneous rock is formed when a magma chamber
cools.
17. What is the name of the rock type which is
formed by re-heating?
Metamorphic rock is formed by re-heating.
18. What is the name of the place where water
erupts from the ground?
It is called a geyser.
19. How does a geyser erupt?
When water in an underground chamber is brought to a
boil, steam builds up within the chamber until it erupts.
20. How often does Old Faithful erupt?
Old Faithful erupts about once every hour.
2 1 . What can you find within layers of
sedimentary rock?
Fossils, oil, gas, and coal deposits can be found
within layers of sedimentary rock.
22. What important things do we obtain from the
earth's crust?
Fossil fuels and mineral resources can be found in the
earth's crust.
DISCUSSION QUESTIONS
These questions are designed to
encourage classroom discussion
1. The video discusses how scientists detonate
surface explosives, and then measure the time
it takes shock waves to bounce off materials in
the earth's interior. In this way, they are able
to determine what's inside the earth without
seeing it.
What other technologies enable us to "see" things
without actually seeing them?
Answers include: radar, sonar, magnetic resonance
imaging, infrared detection, electron emission
microscopy, thermal and radio astronomy.
2. There is an old saying that "if you dig a deep
enough hole you can come out on the other side
of the earth in China". While not discussed in
the video, scientists have drilled holes deep
into the earth in an attempt to determine its
internal composition.
Why is drilling not an effective technique for
analyzing the earth's interior?
While useful for shallow depths, drills are unable to
penetrate more than a few miles beneath the surface.
What type of devise might be designed to penetrate even
deeper into the earth?
Answers will vary. Perhaps laser technology will
provide an answer, or some yet-to-be developed
technology.
10
3. The video discusses how earthquakes occur
near faults in the earth's crust.
What is the likelihood of earthquake's occurring in the
area in which you live?
While faults exist everywhere, some areas of the world
are more earthquake-prone than others. This is because
faults situated near plate boundaries are more likely to be
triggered than those farther away. In the United States, a
plate boundary exists along the western edge of the
country, so there are more earthquakes there than the
eastern United States.
4. Mountain building is discussed in the video.
Are the world's mountains increasing or decreasing in
size?
The world's youngest mountains are increasing in size as
the amount of growth (a couple of inches a year, on
average) exceeds the amount of erosion. Older mountains
are no longer growing and are gradually being worn away.
Name some mountains close to you. Are they fault -block
or folded mountains?
Answers vary with locality. The Appalachians and
Adirondacks and most eastern mountains are folded
mountains. The Sierra Nevada, Tetons and many other
western mountains are fault-block. The Rocky
Mountains have features of both types. The Cascade
Range of the Pacific Northwest are volcanic mountains.
11
The video features lava fountains, lava
curtains and lava rivers.
How do you suppose they got these names? Because
they resemble fountains, curtains and rivers.
Geothermal energy is discussed in the video.
What might be some of the advantages and
disadvantages of geothermal energy in comparison to
traditional energy sources ?
A big advantage is that it is nonpolluting. A
disadvantage is that there aren't many geothermal
areas.
The video discusses how our cities are built of
materials taken from the earth's crust.
Visit areas of your school, both inside and out. What
kinds of things do you find that are made from materials
from the earth?
Answers include all metal, glass, stone, and petroleum
products.
12
ACTIVITIES
1. The video discusses how scientists detonate
surface explosions, and then time the shock
waves, after they bounce off material in the
earth's interior and return to the surface.
Activity: Have students bounce balls while kneeling
and standing. The balls take longer to return while
students are standing, indicating a greater distance to the
floor.
2. The earth's interior is revealed through
animation in the video.
Activity: Have students draw a cross-sectional view
of the earth, highlighting the interior layers in different
colors.
3. The video discusses how stress builds along a
fault before it slips with a sudden jerk.
Activity: This can be mimicked by having students
press their hands together and then try to slide one past
the other. Often, their hands will slip with a sudden jerk.
The video discusses how folded mountains are
made when the earth's crust is squeezed
together.
Activity; This can be mimicked by having students
lay out a hand towel and then slide the edges together
until the towel rises up in folds.
13
5. The video features lava erupting from a
volcano.
Activity; Students can make their own erupting
volcano by first constructing a volcano out of papiermache, plaster of Paris, clay, or other suitable material,
making sure to include a vent. Next, pour a few
tablespoons of baking soda into the vent, followed by a
similar amount of vinegar. The baking soda reacts with
the vinegar, producing a foam which simulates lava
during a volcanic eruption.
6. The video discusses three rock types:
igneous, metamorphic and sedimentary.
Activity; Have students refer to rock identification
books so they can locate and bring in examples of each
rock type.
7. The video discusses how rock can absorb
water.
Activity; Have students soak a piece of sandstone in a
beaker filled with water and note how the water level
changes as the water is absorbed by the rock.
8. The video discusses geothermal energy.
Activity; Have students research and report on the
practicality of geothermal energy versus other energy
sources.
9. The video lists many products we obtain
from the earth's crust.
Activity; Have students list twenty-five products that
are made of materials taken from the earth's crust.
14
GLOSSARY
absorb: suck up or drink in
ancient: old
coarse: having a rough texture
compress: press together
crevice: crack
crust: thin, outermost layer of the earth
erupt: burst forth
evaporate: turn to vapor
fault: crack in a rock, one or both sides of which have
moved in relationship to the other
fault-block mountains: mountains formed by the
uplifting of surface faults
folded mountains: mountains formed by the bending of
the earth's crust
fossil: remains of an animal or plant from a former era
fossil fuel: naturally occurring fuel such as coal, gas and
oil, formed from the remains of prehistoric organisms
gaseous: having the characteristics of gas
geothermal: pertaining to the internal heat of the earth
geyser: hot spring that intermittently sends up fountain-like
jets of water and steam into the air
15
gouged: having been dug or forced out
granite: very hard and durable igneous rock
graph: diagram
hot springs: mineral spring having very warm water
igneous rock: rock produced under great heat
inner core: solid innermost layer of the earth
lava: molten rock that erupts from the earth
lava curtains: lava that erupts through a long crack in the
earth's surface, in the form of a curtain
lava fountains: lava that erupts like a fountain, shooting
high into the air
magma: name for lava before it reaches the earth's surface
magma chamber: reservoir of magma located in the
earth's crust
mantle: mostly molten layer of the earth located below the
crust
marble: hard, durable metamorphic rock that can be highly
polished
metamorphic rock: rock type that has undergone change
network: netlike combination of interrelated elements oil:
dark viscous fluid useful as a lubricant and a fuel origin:
source from which something is derived
16
outer core: molten layer of the earth located below the
mantle
plates: rigid, moving pieces of the earth's shell
precious: highly valued
pressure: exertion of force upon a surface
principle: basic law or rule
resources: things that have value
riddled: pierced with many holes
rigid: stiff, hard
saturated: soaked
sedimentary rock: rock formed by the depositions of
sediment
seismic wave: shock wave caused by the slipping of a
fault
shell: outermost layer of the earth including the crust and
outer portion of the mantle
shock wave: energy wave caused by the slipping of a
fault
skeleton: supporting framework stress: forces executed
by one thing or another transformed: changed in form,
appearance or structure vent: opening in a volcano
17
BIBLIOGRAPHY
Ballard, Robert D. Exploring Our Living Planet.
National Geographic Society, Washington, D.C
1983.
Bernstein, Leonard and Wong, Harry K. Earth Science.
2nded. Globe Book Co., New Jersey, 1979.
Calder, Nigel. The Restless Earth. The Viking Press,
1972.
Cattermole, Peter and Moore, Patrick. The Story of the
Earth. Cambridge Univ. Press, 1985.
Clark, John. Earthquakes to Volcanoes. Gloucester Press,
New York, 1992.
Editors of Time-Life Books. Volcano. Time-Life Books,
Alexandria, VA, 1982.
Erickson, Jon. Rock Formations and Unusual Geologic
Structures. Facts on File, Inc., New York.
Erickson, Jon. Volcanoes and Earthquakes. Tab Books,
Inc., 1988
Frances, Peter and Jones, Pat. Images of Earth. Prentice
Hall, Inc., New Jersey, 1984.
Harris, Stephen L. Fire and Ice. Pacific Search Press, 1980.
Harris, Stephen L. Agent of Chaos. Mountain Press
Publishing Co., Missoula, Montana, 1990.
18
Kaye, Glen. Hawaii Volcanoes. KC Publications, 1976.
Lutgens, Frederick and Tarbuck, Edward. Essentials of
Geology, 4th ed. Macmillan Co., New York, 1989.
Marvin, Ursula. Continental Drift. Smithsonian Institution
Press, 1973.
Mather, Kirtley F. The Earth Beneath Us. Random
House, New York, 1964.
Miller, Russell. Continents in Collision. Time-Life
Books, Alexandria, VA., 1983.
Redfern, Ron. The Making of a Continent. Times Books,
New York, 1986.
Simpson, Brian. Minerals and Rocks. Galahad Books, New
York, 1974.
Van Cleave, Janice. Earthquakes, Spectacular Science
Projects. John Wiley & Sons, New York, 1993.
Van Cleave, Janice. Volcanoes, Spectacular Science
Projects. John Wiley & Sons, New York, 1994.
Van Rose, Susanna and Marcer, Ian F. Volcanoes. British
Museum, 1991.
Van Rose, Susanna. Volcano & Earthquake, Alfred A.
Knopf, 1992.
Walker, Bryce. Earthquake. Time-Life Books,
Alexandria, VA., 1982.
19
Weiner, Jonathan. Planet Earth. Bantam Books, New
York, 1986.
Wright, Thomas and Takahashi, Taeko and Griegs, J.D.
Hawaii Volcano Watch. Univ. of Hawaii Press,
1992.
Zike, Dinah. The Earth Science Book. John Wiley &
Sons, Inc. 1993.
20
SCRIPT
Every few years in Hawaii, hot liquid rock called lava erupts
from deep within the ground, shooting high into the sky.
Where does lava come from?
In Yellowstone Park, boiling water erupts from geysers.
Where does the water come from? How did it get so hot?
In many places around the world, pumps are used to pump oil
out of the ground.
Where does the oil come from?
Oil, water, lava: these are just a few of the things that come
from deep within our earth.
You can learn a lot about the world by looking at a globe. It
shows the continents, the oceans, the locations of mountains
and other land forms.
But a globe can show you only what's on the surface of our
planet.
Have you ever wondered what's inside the earth?
Nobody has ever been to the center of the earth, so how do
we know what's there?
If you bounce a ball, while standing, the ball will return in
about a half-second.
But if you kneel down, the ball returns much more quickly.
You can figure how close you are to the floor just by
measuring the time it takes for the ball to return.
21
This is the same principle scientists use to determine what's
inside the earth.
But they don't use balls, they use explosives.
When an explosion is set off near the earth's surface, it creates
shock waves that move toward the center of the earth. When
the waves strike certain objects, the waves bounce off,
returning to the earth's surface, where they cause vibrations
which can be measured by machines like this.
By studying these vibrations, scientists are able to learn a lot
about the materials that make up the interior of our planet.
What they've learned is that the earth's interior consists of
several different layers:
the inner core which is believed to be solid iron and which is
very hot;
the outer core which consists of rocky material so hot and
under such great pressure, it is in a liquid state;
the mantle which is not quite so hot as the outer core and not
so liquid.
No one has ever seen the mantle, but scientists believe
mantle material may resemble lava which erupts from
volcanoes.
The mantle's outermost portion is solid. This is the solid outer
portion of the mantle.
Above this is the outermost layer of the earth.. .the crust.
Together, the crust and solid outer portion of the mantle
form the earth's outer shell. They are referred to as the
lithosphere.
22
It's not always easy to see the earth's crust, it is covered by
vegetation and oceans.
But if you could drain the oceans and strip away our planet's
vegetation, the earth might look something like this.
Now you can see the earth's hard outer shell. And if you
look closely, you can also see the shell is cracked.
The red glowing lines mark the places where the earth's shell is
cracked into small and large pieces called "tectonic plates".
Each plate carries a continent, or an ocean basin, or sometimes
both. The plates are moving one to two inches a year in different
directions carrying continents and ocean basins with them.
Millions of years ago, the world looked something like this:
every continent in a different position. They were so close
together, they formed a single supercontinent called Pangaea.
But even then, the plates were moving, a few inches a year, and
kept moving until they reached their present-day positions. The
theory that continents move is called "continental drift".
The grinding of plates has been going on for so long, that
most of the earth's crust is filled with cracks, the way this
rock is filled with cracks.
And so it is with the earth's crust, except the cracks aren't so
easy to see because of all the vegetation that covers the land.
But in some places, like deserts, where there is little vegetation,
sections of crust have been exposed and here you can see cracks
that run through the rock that makes up the crust. Many cracks
are small.. .but others, like this surface crack, are hundreds of
miles long.
23
Some cracks in the earth's crust are called faults, and faults are
places that are important to scientists.
One side of the fault tries to move in one direction. The other
side may try to move in the opposite direction. But the two
sides are locked in place. They can't move until enough stress
builds up to move them.
If you bend a stick slowly, you will find it won't break until
sufficient stress builds up.
That's what happens deep underground. The fault will remain
locked until enough stress builds up, and then it will suddenly
release, as one side of the fault slides past the other with a
tremendous burst of energy. The energy that is released is in
the form of seismic waves which radiate or move outward.
If you've ever thrown a stone into a pond, you've seen
waves move outward in all directions.
The waves in this pond are similar.. .to the waves caused by
movement along a fault.
If the disturbance is big enough, the waves will eventually
reach the surface, where they can cause considerable surface
movement, which is referred to as an earthquake.
Each year there are thousands of earthquakes throughout the
world. While most are small, some are large, like this one
which struck in California. While it lasted only 15 seconds, 67
people were killed and damage was widespread.
Some faults occur near the earth's surface, and over millions of
years, and countless earthquakes, one side of the fault may rise
above the other side.
Uplifted sections may rise miles into the sky. They are
called mountains.
24
Fault-block mountains.
These mountains in Wyoming are good examples of faultblock mountains. They rise nearly two miles over the valley
beneath them. This line shows how one section of the earth's
crust has risen above another section.
Mountains are the highest places on earth and are dramatic
evidence of the great forces at work in our planet.
Many of the world's great mountains were formed when one
block of crust rose above another, but other mountains were
formed in a different way.
Millions of years ago, the plate carrying India collided with
the Eurasian plate. Over millions of years, the earth's crust
was squeezed into folds more than five miles high.
The mountains created in this collision are called the
Himalayas and are the highest mountains in the world.
You can make your own folded mountains, simply by
squeezing the ends of some towels together. The earth's crust
will fold just as these towels will.
It's not always easy to see the folds because the mountains
have been worn into jagged peaks by the effects of water,
wind and ice. But if you look closely, you can see how rock
has been folded under the great stresses caused by moving
plates.
This outline gives you an idea of what these mountains may
have looked like when they were much younger.
Mountains are so high, it's surprising what you can sometimes
find there. Fossils of sea life can be found in just about every
mountain range in the world. The fossils got there when layers
of the earth's crust were thrust into the air.
25
We're all familiar with Hawaii's volcanoes, and how hot liquid
rock, called lava, erupts from them. Have you ever wondered
where the lava comes from?
Lava is known as magma before it erupts, and it originates
from deep within the earth, near the mantle.
In some places, magma will rise, finding its way through the
crust into a large reservoir in the volcano, referred to as a
magma chamber. The chamber swells. The ground may
bulge, causing small, localized earthquakes. An eruption can
occur at the end of one or more of several channels.
The lava can shoot hundreds of feet into the sky, and an
eruption like this can last for days. Lava fountains are typical
of these kinds of volcanoes.
Lava can also erupt through cracks in the ground, creating
walls of fire, or lava curtains.
A lava curtain can sometimes be more than a mile long and
reach a height of over 150 feet.
When lava travels downhill, it creates rivers of fire.
In some places, the lava slows to a stop, hardening into black
rock as it cools. But in other places, the lava doesn't stop,
reaching the ocean.
Steam explosions are common, as the lava explodes as it
hardens.
New shorelines form under clouds of hissing steam.
The Hawaiian Islands were formed entirely in this way,
from lava that has hardened into rock.
26
Sometimes, when magma rises from the mantle, it never
reaches the earth's surface.
Instead, it can collect in large reservoirs in the crust. These
reservoirs are also called magma chambers and they can reach
for miles in all directions. The chambers may exist for
thousands of years, before they finally cool and harden into
rock. The rock will remain underground until it is uplifted by
other forces.. .and water and wind wear away the softer rock
above it, and the chamber becomes exposed at the surface.
The mountains in Yosemite Park as well as many other places,
are made of rock that was once part of an ancient magma
chamber that has since been uplifted, and then sculpted by the
effects of water, wind and ice.
Many of the rocks we find on the earth's surface were once
magma that had cooled beneath the ground. Rock formed by
the cooling of magma and lava is called.. .igneous rock.
Igneous means fiery, and these rocks are varied in appearance.
Some igneous rocks, like granite, are very hard. Granite is used
for the exterior of many modern buildings. Pumice is a soft
igneous rock. You can easily scrape it with your nail. Obsidian
is an igneous rock that looks like glass. It can have sharp
edges.
Another type of rock is called.. .metamorphic rock.
Metamorphic rocks originally began as other forms of rock but
have since been changed by heat and pressure found in the
earth.
Some metamorphic rocks clearly show the effects of reheating.
Notice the wavy pattern in this rock. It was formed when the
rock was hot and liquid-like. Some metamorphic rocks
undergo a change in appearance after they've been re-heated.
Marble is a metamorphic rock that started out as limestone, a
different looking rock. Yet other metamorphic rocks undergo
little change in appearance. Slate is a metamorphic rock that
started out as shale, a rock that looks nearly identical to slate.
27
Just as magma finds its way up through cracks in the earth's
crust.. .water finds its way down. Much of the water that falls
on land, soaks into the ground, or finds its way down through
cracks in rock. Rocks can actually absorb water.. .
just as a sponge can absorb water, and this next demonstration
will show you how.
First, three hundred milliliters of water have been added to a
beaker.
Next, a sandstone rock is placed in the beaker. After several
hours, the rock is removed.
The amount of water remaining - less than 250 milliliters.
More than 50 milliliters are gone. The missing water is in
the rock.
In some places, underground chambers exist in the earth's crust.
Sometimes these chambers occur near magma chambers. When
water finds its way into the crust, it will fill the chambers.
The water becomes heated by the magma and boils. Pressures
build and the expanding steam causes an eruption.
This is similar to what happens when a teakettle boils. But
in nature, the results are a bit more dramatic.
The place where water erupts from the ground is called a geyser.
This one, in Yellowstone Park, is named Old Faithful because
like clockwork, it erupts once every hour.
An hour is how long it takes for ground water to fill the
empty chambers, boil, and erupt again.
Much of Yellowstone Park is situated directly above a magma
chamber, and that's why this area is known for its many geysers
and hot springs.
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Hot springs don't erupt. They just simmer and boil. They've
been boiling like this for thousands of years and may continue
to boil for thousands more.
Each time Old Faithful erupts, it releases a great deal of
energy.. .energy that could be put to work.
That's why in some places where you find geysers and hot
springs, you will find geothermal plants. These plants use the
steam produced by hot springs and geysers to drive other
machines which in turn produce electricity for our homes.
People have been using the things they find in the earth to
make energy for a long time.
One such energy source is oil. To understand how oil finds its
way into the earth, we first have to learn about another type of
rock.
In some places, the earth's crust is exposed in layers like the
layers of a cake. But this cake is millions of years old.
The layers were formed when this part of the earth was under
water and one muddy layer was deposited above another layer.
Over thousands of years, the layers were pressed down by the
new layers above them and turned into rock.. .sedimentary
rock.
You can make your own sedimentary rock simply by mixing
water with some stones, sand and clay.
At the end of the day, you will discover that the water has
evaporated and what is left behind are hardened layers of
sedimentary material.
When you look at layers of sedimentary rock, the newest or
youngest rock is near the top. The oldest is at the bottom.
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Old layers of sedimentary rock may also contain the remains of
ancient plants and animals that lived in oceans and lakes
millions of year ago. Over time and under the heat and
pressure found in the crust, the remains can turn into a rock ..
.we call coal.. .or into a slippery substance we call oil.
Both oil and coal are used as fuels. When they bum, they give
off a lot of heat.
Oil, as well as another fuel, natural gas, exists underground in
the cracks and crevices of the earth and within rock itself.
Some rocks are saturated with oil.
When people drill for oil, they may have to drill thousands of
feet before they can tap into rock that is filled with oil. Then,
the oil shoots to the surface.
Oil and gas are usually found in sandstone. We've already
seen how sandstone absorbs water.
Well, it absorbs oil nearly as easily. Sometimes oil can be
found in shale, another common sedimentary rock, but shale is
very hard, and the oil is very difficult to get out.
In some places the earth's crust has been gouged out so that
miners can reach important mineral resources like gold, silver
and copper. This mine in Utah is the largest open pit mine in
the world.. .the largest hole ever dug. It's two miles across
and over a half-mile deep.
Our cities are built of materials we've taken from the earth.
Iron, stone and glass, which is made from silica, come from
the earth's crust.
In this program, we've seen how scientists use shock waves to
learn more about the earth's interior.
We've seen how the earth's interior consists of several
different layers...
30
and that the earth's outer shell is broken into more than a dozen
plates which move in a variety of directions, carrying continents
and ocean basins with them.
We've seen how the earth's crust is filled with cracks, some of
them called faults.. .and that when a fault slips it releases
energy in the form of seismic waves, causing earthquakes on
the earth's surface.
We've seen how one side of a fault can rise up on end and
become fault-block mountains.
Folded mountains are formed when the earth's crust is
squeezed together creating folds.
We've seen that magma can rise up through the earth's crust,
erupting as volcanoes.. .or, it can remain just beneath the
surface in large chambers.
Magma and lava that harden turn into a variety of rocks known
as igneous rocks. Igneous rock formed underground can reach
the surface, either by uplifting, or when softer rock above it
wears away.
Many mountains contain igneous rock that has risen to the
surface.
Metamorphic rocks are rocks that have become changed
under the heat and pressure found in the earth's crust.
We've seen how water enters the ground by soaking through
soil and rock and by following cracks in the crust.
Geysers and hot springs occur in areas where you find
ground water and magma chambers.
The steam created by geysers and hot springs can be
harnessed to produce electricity.
31
We've seen that a third type of rock is called sedimentary rock
and within some layers you can find coal, oil, and natural gas.
Finally, we've seen how the earth's crust has been mined for
valuable minerals and building materials.
We've taken so much from the earth's crust that when you
ask the question, "What's inside the earth?", you need only
look around.
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CLOZE EVALUATION QUESTIONS
WHAT'S INSIDE THE EARTH?
NAME
DIRECTIONS: Select the answer, from the four choices given, by circling the correct letter.
1. Our earth is an ever-changing place. Changes are often results of what
happens below the surface. The earth's interior consists of several different
layers. The inner core is thought to be made of _____.
1.
A. zinc
B. carbon
C. iron
D. aluminum
2. The outer core consists of rocky material and is very hot and under great
pressure. The next layer, called the _____, consists of a hot, lava-like area on the
inside and a solid outermost portion.
2.
A. crust
B. mantle
C. lithosphere
D. magma core
3. The uppermost layer of the earth is the region we live on. This layer, called the
_____, is affected by what is happening beneath it. The many geologic
formations, like volcanoes and mountains, were formed by forces acting beneath
this upper layer of the earth.
3.
A. crust
B. mantle
C. outer core
D. upper core
4. The crust would look quite different if we could strip away the oceans and plant
life. In many places the crust is cracked. The large pieces of the crust are called
_____. The continents rest upon them and, over millions of years, have actually
moved.
4.
A. landforms
B. land masses
C. countries
D. plates
5. The earth's huge plates have been moving very, very slowly. The movement is
so slight that it is not seen happening. Scientists believe that this process of
movement, called _____, is a major cause of geologic changes on our planet.
5.
A. continental drift
B. transformation
C. subduction
D. volcanism
6.
A. break
B. space
C. fault
D. separation
A. mantle waves
B. seismic waves
C. tidal waves
D. rock waves
6. The grinding of the earth's plates has been going on for millions of years. One
result of this process is a crack in the earth's surface, called a _____. One side of
this crack tries to move in one direction while the other moves in the opposite
direction. The earth's plates remain in position until stress from below causes
them to move.
7. An earthquake occurs when the stress below the surface causes areas on
either side of the fault line to move. When this happens the energy that is
released is in the form of _____. If the disturbance is big enough, the force will
eventually cause damage on the surface of the earth.
8. Scientists classify rocks according to how they were formed. One type of rock,
called _____ rock, was formed by the cooling of a hot liquid material called
magma. There are a number of different types of this rock and one such type is
called granite. This rock is frequently used as building material.
9. Deep within the earth, rocks are under a great deal of heat and pressure.
Another type of rock, called _____ rock, is formed by such heat and pressure.
Sometimes this type of rock is formed by changes in other types of rock. For
example, limestone is changed to marble by heat, pressure and time.
10. In some areas of the earth, rock can be out in the open and seem to have
been formed in layers. This third category is called _____ rock and was formed as
layers and layers of rock were piled upon one another. From this category we get
such natural resources as coal and oil. Some of the rocks in this group are called
fossils and consist of the remains of plant and animal life.
This form may be reproduced without permission from Rainbow Educational Media.
7.
8. A.
B.
C.
D.
metamorphic
sedimentary
magma
igneous
9.
igneous
metamorphic
sedimentary
magma
A.
B.
C.
D.
10. A. sedimentary
B. magma
C. igneous
D. metamorphic