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Name: _______________________ Date: __________
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Pre-Lesson Assessment (3 points)
1.
2.
3.
Of what material(s) is the earth's crust made?
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How do rocks break in nature?
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How would the breaking of a large rock affect people?
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Part 1: Read
We see rocks outside every day, in both landscaping and nature. In fact, the entire earth is basically
one gigantic rock! The earth's crust is entirely made of solid rocks, so there are huge rocks in the
ground covering the entire planet! We cannot see many of these rocks. Sometimes dirt covers them
and we must dig very deep to find them, but huge rocks cover the entire earth's crust, even under the
oceans. That means that all of our buildings, all of our bridges, all of our roads, and even your home,
are sitting on rock.
Part 2: View PPT
http://www.woboe.org/cms/lib8/NJ01912995/Centricity/Domain/867/rock%20solid%20intro%20ppt.ppt
Part 3: Predict (3 Points)
The following are questions that geotechnical engineers think about when determining locations to
place structures. Geotechnical engineers understand what causes rocks to break. They know how to
identify different types of rocks, and determine if a certain rock is likely to break. They work with
structural engineers to plan the best way to build structures in different rock conditions.
1. What might happen if some of these huge rocks broke?
2. What types of natural disasters might be caused?
3. What would happen to the bridge or skyscraper resting upon one of those massive
rocks?
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Part 4: Background Information: READ
Why Care about the Strength of a Rock?
The most important reason why we care about the strength of a rock is that when a large rock breaks,
it can be a hazard and possibly cause a disaster. There are many different disasters caused by
breaking rocks, including earthquakes, tsunamis, volcanoes, rock falls, and landslides. To protect
structures and people, we want to be able to predict or prevent such disasters. If an engineer knows
the characteristics of a particular rock type, she may be able to predict or prevent disasters.
Furthermore, a less serious reason why we care about the strength of rocks is for development,
which means building and expanding the use of land (such as new shopping centers, schools or
homes being built in a town). Many building plans require deep foundations, making it necessary to
excavate or dig out rock. An engineer provides information about the best way to excavate the rock,
so as to build an adequate foundation.
What Can Break Rocks?
When pressure is applied to an area, such as a rock, it is called stress. If you press your hands
together, you can feel the forces of stress. In nature, stress can cause rocks to break, and one way
that stress occurs is by the natural movements of the earth's crust (remember that the earth's crust is
basically floating on liquid magma, and so it moves often). There are three types of stress
Figure 1. Three types of stresses in rocks.
1. Compressional stress is when a rock is pressed together into itself, like when crust
movements cause two rocks to squeeze another one between them. Another example is when
mountains are formed at a convergent boundary, like the Rocky Mountains. Press your hands
together again. You can feel that the inner parts of your hands are being smashed by
compressional stress from the muscles in your hands pushing inward.
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2. Tensional stress is when a rock is pulled apart. For example, if a rock wedged itself into the
crack of another rock, and movement of the earth's crust caused it to wedge even further until
the rock broke apart. Another example is a divergent boundary, like the Mid-Atlantic Ridge,
which is formed by two tectonic plates pulling apart from each other to allow lava to flow
upward. Use one of your hands to pull a finger on your other hand. You can feel the tensional
stress because your hand is pulling your finger one way, and your other hand is attached to
your finger, pulling it the other way by holding it in place.
3. Shear stress is when a rock is pulled on one side but pushed on the other side. This can
happen if the crust movements on one side of a rock are opposite of those on the other side of
the rock. An example of this is the San Andreas Fault, which is on a transform boundary, with
the California plate moving southward and the Pacific Ocean plate moving northward. Put your
hands together again, but this time press upward with your right hand and downward with your
left hand. If you press hard, you should notice that the skin on your right hand is being pulled
down because of the forces from your left hand pulling down, and the skin on your left hand is
being pulled up because of your right hand. (It may be easier to see the skin being pulled if you
use an area on your body where the skin is looser, such as your hand pressing upward against
your arm or cheek.)
In addition to stress due to the movement of the earth's crust, stress can come from
weathering. Weathering is the breaking down of rocks into sediments (small bits of
rock), due to conditions in nature. There are many types of weathering:

Physical weathering is when a physical action breaks the rock, such as the forces of wind or
water. A common example is the freeze/thaw action of water in rock cracks. As the water
freezes, it expands, causing stress (pressure) that breaks the rock. (Note: If students ask what
kind of stress this is, tell them that the process is complicated and includes both tensional and
compressional stress.)

Chemical weathering is when the rock is chemically broken down. Some common examples
of this are rust forming on granite or acid rain breaking down limestone. This type of
weathering is not considered a type of stress because there is no pressure on the rock
(remember that stress is pressure applied to an area).

Biological weathering is when living organisms break the rock. A typical example is a tree
root breaking a rock due to the stress caused by its pressure. (Note: If students ask what kind
of stress this is, tell them that the process is complicated and includes both tensional and
compressional stress.)
So, rocks in the earth are usually broken by either the stress from the
movement of the crust or the stress from weathering.
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Part 5: Lab Exploration
Pressure on Rocks – Soapy Stress Lab
Rocks cover the entire earth, and we need to know how they break. Who can tell me why? If we know how rocks break,
then we can predict many types of natural hazards, which can, in turn, save structures or even our lives. Also, because
we live on the earth and build structures on and in the earth, we need to know about how rocks break. Geotechnical
engineers know all about rocks in the earth's crust. They know how to identify different rocks, and determine if a certain
rock is likely to break. They do tests and simulations to predict volcanoes, earthquakes or rockslides. Geotechnical
engineers also need to know how rocks break so that other engineers can excavate or dig into them to build the deep
foundations or basements of buildings such as parking garages, bridge piers or skyscrapers.
Do you know how rocks break? Well, rocks break from stress. Stress is when pressure is applied to an area, such as a
rock. There are three types of stress. Compressional stress is when something is pressed together, like when mountains
form. Tensional stress is when something is pulled apart, like when a ridge such as the Mid-Atlantic Ridge is
formed. Shear stress is when something is pulled one way on one side and the other way on the other side, like the San
Andreas Fault.
Now that we've reviewed how rocks break, let's demonstrate these types of stresses ourselves! Using our own hands, do
you think we could create enough stress to break a rock? Probably not! What are some things that we can break with our
hands? Soap is a good model because with it, we can show the three different types of stress. Since we are not strong
enough to break rocks, we can imagine that the bars of soap are rocks, and break them in different ways.
Vocabulary/Definitions
compressional
stress:
earth's crust:
erosion:
When something is being pressed together. Causes a rock to shorten.
(geology) The exterior surface of the earth.
Natural processes that wear away material. Includes weathering,
dissolution, abrasion, corrosion and transportation.
Geotechnical
A person concerned with the engineering properties of earth materials. They
engineer:
investigate the soil and rock below ground to determine its properties, and
then design foundations for human-made structures built on the ground,
such as buildings or bridges. They design structures built in or of soil or
rock. They also assess the risk to humans, property and the environment
from natural hazards such as landslides, debris flows and rock falls.
godel:
A small object that represents another, often larger object. Often used in
testing or perfecting a final product.
rock:
A naturally-formed aggregate of mineral matter constituting a significant part
of the earth's crust.
sedimentary rock: (geology) A rock made by the deposition of sediment (small bits of old rock).
Examples: sandstone, siltstone, limestone and shale.
shear stress:
When something is being pulled one way on one side, and the opposite way
on the other side. Causes rocks to slip past each other.
stress:
Pressure applied to an area. The three types are compressional, tensional
and shear.
tensional stress: When something is being pulled apart. Causes a rock to elongate, or pull
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weathering:
apart.
Breaking down of rocks, due to such things as water, wind, acid rain and
plants.
Procedure
MODEL #1
Tensional Stress (When something is being pulled apart.)
1. Choose one team member to place TENSIONAL STRESS on the bar of soap. Watch what
happens carefully. Draw a picture of the soap and how it was broken. Draw arrows showing
the direction of the force placed on the soap. (2 points)
2. Describe the area where the soap broke. (Smooth, rough, jagged, stretched, etc.) (2 Points)
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3. What is a real life example of tensional stress? (5 Points)
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Figure 1. Using tension (pulling apart movement) to break a bar of soap.
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MODEL #2
COMPRESSIONAL Stress (When something is being pushed together.)
1. Choose one team member to place COMPRESIONAL STRESS on one of the pieces left from
the bar of soap. Watch what happens carefully. Draw a picture of the soap and how it was
broken. Draw arrows showing the direction of the force placed on the soap. (2 points)
2. Describe the area where the soap broke. (Smooth, rough, jagged, stretched, etc.) (2 points)
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3. What is a real life example of compressional stress? (5 Points)
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Figure 2. Using compression (pressed together pressure) to break soap.
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MODEL #3
SHEAR Stress (When something is being pulled one way on one side, and the opposite way on the
other side. Causes rocks to slip past each other.)
1. Choose one team member to place SHEAR STRESS on one of the pieces left from the bar of
soap. Watch what happens carefully. Draw a picture of the soap and how it was broken. Draw
arrows showing the direction of the force placed on the soap. (2 Points)
2. Describe the area where the soap broke. (Smooth, rough, jagged, stretched, etc.) (2 Points)
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3. What is a real life example of compressional stress? (5 Points)
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Figure 3. Using shear stress to break soap. One hand pulls up, the other hand pulls down.
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MODEL #4
How might you demonstrate combination stresses using a piece of soap?
(Clue: Try bending a bar of soap to cause both compressional and tensional stresses.)
1. Draw a picture of the soap and how it was broken. Draw arrows showing the direction of the
force placed on the soap. (2 Points)
2. Describe the area where the soap broke. (Smooth, rough, jagged, stretched, etc.) (2 Points)
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3. What is a real life example of combination stress? (5 Points)
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Assessment (6 Points)
Matching: Match the correct pieces together.
Journaling: Answer the following questions in paragraph form.
1. Today we demonstrated the three different types of stress. How would some of
these stresses occur on a bigger scale in the natural world? BE SPECIFIC! (10
Points)
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2. Why do geotechnical engineers need to understand stress in rocks? BE
SPECIFIC! (Hint: think natural disasters, human made objects, etc.) (10 Points)
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Part 6: Interactive Explorations
Kinds of Rocks and How Rocks Are Made
1. Go to: http://www.learner.org/interactives/rockcycle/types.html
2. Fill in this table: (9 Points)
Name of Rock
How it Forms
Example
3. READ this chart
Here's a chart of some of the key characteristics that can
help you identify the rocks within these three main classes.
Crystals
Small, flat
surfaces
that are
shiny or
sparkly, like
tiny mirrors.
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Fossils
Imprints of
leaves,
shells,
insects, or
other items
in the rock.
Gas
bubbles
"Holes," like
Swiss
cheese, in
the rock.
Glassy
surface
A shiny and
smooth
surface, like
colored
glass.
Ribbonlike
layers
Straight or
wavy
stripes of
different
colors in the
rock.
Sand or
pebbles
Individual
stones,
pebbles, or
sand grains
visible in
the rock.
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4. START YOUR ROCK COLLECTION:
Go to: http://www.learner.org/interactives/rockcycle/types2.html
5. Click on and read about each of the 6 rocks. WHEN YOU ARE DONE SHOW
YOUR TEACHER for her initials. _____________ (Teacher Initials) (5 Points)
6. IDENTIFY ROCK TYPES:
Go to: http://www.learner.org/interactives/rockcycle/types3.html
7. Play until you get 10 out of 10 correct. WHEN YOU ARE DONE SHOW YOUR
TEACHER for her initials. _____________ (Teacher Initials) (10 Points)
8. HOW ROCKS CHANGE:
Go to: http://www.learner.org/interactives/rockcycle/change.html
Complete the three pages of the interactive. (Click next to go to each new page.)
9. Change a Rock Interactive
Go to: http://www.learner.org/interactives/rockcycle/change4.html
10.
Complete the interactive. WHEN YOU ARE DONE SHOW YOUR TEACHER
for her initials. _____________ (Teacher Initials) (5 Points)
11.
THE ROCK CYCLE DIAGRAM
Go to: http://www.learner.org/interactives/rockcycle/diagram.html and read the
diagram.
12.
ROCK CYCLE DIAGRAM INTERACTIVE
Go to: http://www.learner.org/interactives/rockcycle/diagram2.html
13.
Play until you get 10 out of 10 correct. WHEN YOU ARE DONE SHOW
YOUR TEACHER for her initials. _____________ (Teacher Initials) (10 Points)
14.
TEST YOUR SKILLS
Go to: http://www.learner.org/interactives/rockcycle/testskills.html
15.
Take the test. If you score below and 80% refresh the page and do it again.
WHEN YOU GET TO AT LEAST 80% SHOW YOUR TEACHER for her initials.
_____________ (Teacher Initials) (10 Points)
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Post Assessment Rock Cycle Diagram (20 Points)
You may have noticed in learning about the different rock families that all new rocks are made from
old rocks. This is the idea behind the rock cycle (see Figure 6). For example, under certain
geophysical processes, a metamorphic rock can be formed from a sedimentary and/or igneous rock.
Likewise, all rocks can become every other type of rock given the right circumstances. The rock cycle
describes the processes that allow the creation of new rocks from old rocks.
Use boxes or circles to show the different stages of rocks. Use arrows to show the changes in your rocks.
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Post-Lesson Assessment
1.
Of what material(s) is the earth's crust made? Give specific examples. (2 Points)
________________________________________________________________
________________________________________________________________
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2.
How do rocks break in nature? (2 Points)
________________________________________________________________
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3.
How would the breaking of a large rock affect people? (2 Points)
________________________________________________________________
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Teacher Notes
1. Day 1 – Video, Rock Solid Part 1-4 and when completed book
questions about erosion and weathering.
2. Day 2 – Part 5 – Soap lab
3. Day 3 and 4 – Rest of sections….Part 6 and post assessment
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