Download Peanut Butter and Jelly Geology

Peanut Butter and Jelly Geology
A Study of Faults and Geologic Activity
Over
ervview
California’s diverse landscape and
complex geology can be attributed to
tectonic faulting. Earthquakes,
volcanoes, erosion, uplift--all have
played a role in shaping our landscape. In this activity students
explore the connections between the
topography of the Bay Area and the
geological processes that underlie it.
They will learn about sediment
types, plate tectonics, and how they
affect the topography of the Bay Area
and its surrounding landscape.
Estimated Time
1 hour
Objectives
Students will be able to:
• Describe various faults and their movements
• Define and describe plate tectonics
• Explain folding and faulting forces of
various plate boundaries and their
impacts on the geology of the Bay
•
•
•
1 clear plastic straw
1 plastic knife
1 small paper cup of mixture of food items
such as raisins, oats, cereal, etc. (optional)
Vocabular
ocabularyy
Blocks, core, crust, fault, normal fault, strike-slip
fault, graben fault, subduction, plate tectonics,
rocks, sediments, core sampling
Materials
Part I: Introduction to Geology
For each student
• 1 oreo cookie
• 1 napkin
California Science Content Standards
Part II: Plate Tectonics and Peanut Butter
Make groups of 4-5 students, for each group
• 1 copy of the Student Pages of Peanut
Butter and Jelly Geology for each student
• 1 small paper cup of peanut butter
• 1 small paper cup of jelly
• 4 slices of bread
• 1 flat paper plate
Grade 7
Grade 6
Standard Set 1.e: major geologic events, such
as earthquakes, volcanic eruptions, and
mountain building result from plate motions.
Standard Set 1.f: how to explain major features
of California geology in terms of plate tectonics
(including mountains, faults, volcanoes).
68 Save The Bay’s San Francisco Bay Watershed Curriculum
Standard Set 4.a: Earth processes today are
similar to those that occurred in the past and
slow geologic processes have large cumulative
effects over long periods of time.
Grade 7 (continued)
Standard Set 4.c: the rock cycle includes the
formation of new sediment and rocks. Rocks
are often found in layers with the
oldest generally on the bottom.
Standard Set 4.f: how movements of the
Earth’s continental and oceanic plates through
time, with associated changes in climate and
geographical connections, have affected the
past and present distribution of organisms.
Grades 9-12
Earth Sciences Standard Set 9.a: the
resources of major economic importance in
California and their relation to California’s
geology.
best places to observe faults are usually in
roadcuts, quarries, and sea cliff exposures.
Fault Classification
Faults and fault zones are classified by how the
rocks on each side of the fault or fault zone move
past each other. There are two main types of
movement along faults: 1) a sideways movement called strike slip, and 2) an up or down
movement called dip slip.
Strike-Slip Faults
The movement along a strike-slip fault is
approximately parallel to the strike of the fault,
meaning the rocks move past each other
horizontally.
Additional Resources
This activity was adapted from “Estuarine Encounters” by
Friends of the San Francisco Estuary.
http://www.abag.ca.gov/bayarea/sfep/programs/ested/
index.html#estenc
USGS Quake Info
http://quake.wr.usgs.gov/
Kids GeoZone
http://www.consrv.ca.gov/CGS/information/
kids_geozone/index.htm
Paper Models from USGS
http://interactive2.usgs.gov/learningweb/teachers/
paper_models.htm
Background
A fault is a fracture along which there is
movement. Some faults are actually composed
of several fractures called fault branches.
Collectively the branches are a fault zone. (see
map on front page of activity)
California’s diverse landscape and complex
geology can be attributed to faulting. Many of
the State’s valleys, mountain ranges, and desert
areas show the effects of faulting. Faults create
underground traps in which valuable reservoirs
of petroleum form, and spaces in which
underground waters deposit valuable metals in
the form of veins and masses of ore. Faults are
distinguished by abrupt changes in rock
structure or composition. Sometimes a fault
can be recognized by the displacement of a
particular feature such as a bed or a vein. The
The San Andreas is a strike-slip fault that has
displaced rocks hundreds of miles. As a result of
horizontal movement along the fault, rocks of
vastly different age and composition have been
placed side by side. The San Andreas fault is a
fault zone rather than a single fault, and movement may occur along any of the many fault
surfaces in the zone. The surface effects of the
San Andreas fault zone can be observed for over
600 miles (1,000 km).
Dip-Slip Faults
Dip-slip faults are faults on which the movement is parallel to the dip of the fault surface.
Normal faults are dip-slip faults on which the
hanging wall (the rocks above the fault surface)
move down relative to the footwall (the rocks
below the fault surface). Normal faults are the
result of tension (forces that pull rocks apart).
Where the dip of a normal fault’s surface is
steep, it is called a high-angle normal fault, or
simply a normal fault. The Owens Valley and
the Sierra Nevada fault zones are examples of
high-angle normal faults. Together they produce a down-dropped block which forms the
Owens Valley. This type of fault-bounded valley
is called a graben. A fault-bounded ridge is called
a horst.
Save The Bay’s San Francisco Bay Watershed Curriculum 69
The Sierra Madre fault zone of southern
California is an example of reverse-fault movement. There the rocks of the San Gabriel
Mountains are being pushed up and over the
rocks of the San Fernando and San Gabriel
valleys. Movement on the Sierra Madre fault
zone is part of the process that created the San
Gabriel Mountains.
Where the dip of a normal fault’s surface is very
gentle or almost flat, it is referred to as a
detachment fault or low-angle normal fault.
Detachment faults are common in the desert
areas of California.
Reverse faults are dip-slip faults in which the
hanging wall moves up relative to the footwall.
Reverse faults are the result of compression
(forces that push rocks together).
A thrust fault is a reverse fault with a gentlydipping fault surface. Thrust faults are very
common in the Klamath Mountains of northern California.
Notes
The terms normal and reverse were first used by
English coal miners to describe faults. When
working a flat coal bed where it was dislocated
by a normal fault, the miners continued the
workings either upward or downward on the
fault surface in the same, or normal, direction.
The workings in a seam dislocated by a reverse
fault were also continued upward or downward
on the fault, but in the opposite, or reverse,
direction (Ojakangas, 1991).
The terms hanging wall and footwall are also old
mining terms. These terms were originally used
in inclined underground passageways to refer to
the rock “hanging” overhead (the hanging
wall) and the floor beneath the miners’ feet (the
footwall) (Ojakangas, 1991).
This background information was taken from the California
Conservation web site at
http://www.consrv.ca.gov/cgs/information/publications/teacher_features/faults.htm
70 Save The Bay’s San Francisco Bay Watershed Curriculum
Teacher PPrroc
edur
ocedur
eduree
Par
oduction to Geolog
artt I: Intr
Introduction
Geologyy
(cream side up) and slowly push it below
the other piece of cookie so that the cream
scrapes onto the top cookie piece.
1. You can start off by asking the students
some simple questions:
• Do you know how landscape around the
Bay such as mountains is formed?
• What is a fault?
• Have you ever heard of the term plate
tectonics? Do you know what it means?
9. Now let your class try it.
2. Tell your students that they will be using
everyday items to represent the earth and
explore how natural forces alter and shape
the geology of the San Francisco Bay and its
surrounding landscape. Their model will
help them answer these questions about
earth science.
10. Tell the class that the process of one plate
sliding beneath another is called subduction
and that much of the land around the
Estuary is composed of rocks that were
altered during subduction. This mixture of
rocks that were formed from a scraping of
the plates and from subduction make up the
bedrock found around much of the Estuary.
11. Explain that although subduction no longer
affects the geology of the Bay Area, it affects
other areas in the world, and often leads to
volcanoes and tsunamis.
3. Pass out one oreo cookie to each student.
12. Now let your class eat the cookies!
4. Tell the students to carefully twist off the
top part of the cookie so that they have the
two pieces separated and one piece has all of
the cream on it.
5. Demonstrate this procedure to the class.
6. Explain to them that they are going to
pretend that these two pieces of cookies are
tectonic plates of the Earth and that they
are going to study the movement of these
plates and how they changed the sediments
and geology in the Bay Area.
7. Tell them that the process they are going to
learn is called subduction and it occurs
when one plate moves under the other and
the top plate scrapes sediments off the
bottom plate while the bottom plate is
diving under.
8. Demonstrate the process of subduction
while explaining that the Earth’s plates
have different types of movements that
create different types of structures. Take the
oreo cookie with the cream on top
Par
te T
ectonics and PPeanut
eanut B
utter
artt II: Pla
Plate
Tectonics
Butter
1. Tell your class that they are going to
perform another experiment to help
demonstrate other ways that plates and
faults move and learn how that has shaped
the Bay. Divide the students into groups of
4 or 5.
2. Pass out the materials and the student pages
to each group. (The following directions are
also on the student pages). Assist the
students as they follow their written
instructions and ask discussion questions.
3. Each group will start by spreading peanut
butter on two bread slices and jelly on the
other two slices (without joining the slices
together).
*Optional: Students can also add small foods
like raisins, oats, cereal, etc. to represent
different rocks and minerals.
4. When all the groups are ready, instruct the
students to put their sandwiches together
Save The Bay’s San Francisco Bay Watershed Curriculum 71
by alternating peanut butter and jelly slices
(plain bread sides facing out).
5. Explain to the students that the stack is the
bottom of the Pacific Ocean long ago, and
that the stack represents the different layers
of sediment that have accumulated over
thousands of years.
6. Explain the theory of plate tectonics, that
the Earth’s crust is made up of 12 different
plates that move against each other. The
boundaries of these plates is where rock
deformation occurs. Tell the class that they
are going to use their stack to help them
visualize some of the effects of plate tectonics.
7. Ask “What happens to rocks when they are
exposed over time to pressure and heat?”
Explain that as the ocean floor sediments
were scraped against the continent, pressure and heat caused the rocks to metamorphose/deform. Also that deformations
occur along plate boundaries. Introduce
this concept of folding and faulting due to
heat and pressure.
8. Tell them to demonstrate this by applying
compressional pressure to the outsides of
the sandwich stack, causing the stack to fold
and buckle, creating small ridges and
valleys. The Student Pages contain a
diagram illustrating this and explaining it
to the students. This process created many
mountain ranges around the world.
9. Now have the students cut their sandwich
stacks in half lengthwise. They can demonstrate the strike-slip movement between
two blocks by sliding the two blocks
towards each other and then horizontal to
each other, following the diagrams in their
Fault Activity Demo Sheet. The San
Andreas Fault has this type of motion.
10. Next the students should cut one of the
halves of their sandwich stack in half again,
creating two blocks. They can use these to
demonstrate a normal fault by pushing the
two blocks against each other and having
one block slide downwards against the
other(normal fault). Then have one slide
upwards against the other (reverse fault).
The Owens Valley and Sierra Nevada fault
zones are examples of normal faults. The
Sierra Madre fault zone is an example of a
reverse fault movement.
11. The graben fault is a special type of normal
fault. The graben fault can be shown by
cutting the remaining sandwich stack into
thirds and exerting force on the outer thirds
to push the inner third downward. Point
out which sections are the graben and horst.
12. Now show your students a core sample by
taking a clear straw and inserting it carefully
through the stack of bread slices. Twist the
straw as you insert it into the densest part of
the sandwich. After removing the straw,
discuss the profile, showing the pattern of
materials (the alternating layers of peanut
butter and jelly represent the different layers
of rock).
13. Explain how the stratified sediments
represent the layers of sedimentary rock that
were scraped off from the ocean bottom to
the continental margin, then moved,
through faulting and folding to their
present locations around the Estuary. Some
of these rocks deposited along the coast of
California and created the Coastal Mountain range.
14. Have them take a core sample of their
stacks.
15. Discuss with your students that rock layers
are laid down horizontally. Let the groups
discuss which layers in their model are the
oldest and youngest layers of rock. Review
72 Save The Bay’s San Francisco Bay Watershed Curriculum
their answers and teach them that “If rock
layers are not disturbed the oldest layers are
on the bottom and the youngest layers are
on the top.” Explain to them that this helps
geologists chronologically date rock layers
and formations.
Clas
sion/W
rap Up
lasss Discus
Discussion/W
sion/Wrap
1. Begin a discussion that summarizes what
has occurred. Review:
•
•
•
•
Subduction and how it forms new earth
How faults and plate boundaries create
mountains and valleys
The differences between the 3 faults we
studied
Significance of core samples and what
they teach us
2. Divide the sandwiches and serve.
3. You can build paper fault models with your
class as well. Research the “Mapping Our
Faultlines” Activity on the USGS web site
from USGS Learning Web, U.S. Department of Interior, U.S. Geological Survey,
Reston, VA. USA.
http://www.usgs.gov/education/
Save The Bay’s San Francisco Bay Watershed Curriculum 73
Peanut Butter and Jelly Geology
A Study of Faults and Geologic Activity
INTRODUCTION
Throughout history, geology has shaped and changed the landscape of the San Francisco Bay Area.
Natural forces such as plate tectonics, sediment movement, and water flow have formed the land
into the mountains, valleys, creeks, and rivers we see today. Look at the area around your home or
your school; what natural forces might have shaped the features we see today? In this activity you
will get a chance to explore the geologic forces that have created not only the San Francisco Bay as
we know it, but also a lot of the landscape we see surrounding the Bay Area, such as the Sierra
Nevada mountains and the Central Valley. You will use everyday food items to represent various
tectonic plates in order to learn about how the plates move and how this movement has created
our local landscape. Finally you will get to eat your “plate tectonic models” and enjoy a tasty
treat!
MA
TERIALS
MATERIALS
Your group will need
• 4 slices of bread
• 1 paper plate
• 1 plastic knife
• 1 plastic cup of peanut butter
• 1 plastic cup of jelly
• 1 plastic cup of snack mixture (optional)
74 Save The Bay’s San Francisco Bay Watershed Curriculum
PROCEDURE
1. Spread peanut butter on two slices of bread and spread jelly on the other two slices. DO NOT
PUT SLICES TOGETHER YET!
2. You may sprinkle some of the snack mixture on the slices if you have some. (optional)
3. When your teacher tells you to, put your slices together. Alternate the slices between peanut
butter and jelly and put them together as you would a normal sandwich.
4. Discuss among your group: “What happens to rocks when they are exposed over time to
pressure and heat?” How would expect your sandwich model of rock layers to change in
appearance if subjected to heat and pressure?
5. Observe your teacher demonstrate the process of folding and faulting.
6. Then try it with your group. (Refer to your Fault Activity Demo Sheet.) Slowly bend the stack
up toward the center; push in from the edges to mimic the process of folding. Folding and
faulting created the Himalayan mountain range and many other ranges in the world.
7. Now cut the stack in half through the middle, forming 2 blocks and slide them to show strikeslip movements of the Earth’s crust. Demonstrate the strike-slip movement between two
blocks by sliding the two sandwich blocks against each other and then horizontal to each other,
following the diagrams on the Fault Activity Demo Sheet. The San Andreas Fault has this type
of motion.
8. Cut one of your sandwich stack halves in half and show the vertical motion of the plates when
pushed against each other. Use these sandwich blocks to demonstrate a normal fault by pushing the two blocks against each other and having one block slide downwards against the other
(normal fault). Then have one slide upwards (reverse fault) against the other. The Owens Valley
and Sierra Nevada fault zones area examples of normal faults. The Sierra Madre fault zone is an
example of a reverse fault movement.
9. Then cut another of your stacks in thirds to show the formation of a valley, a graben fault
movement. The graben fault is a special type of normal fault. The graben fault can be shown by
cutting the remaining sandwich stack half into thirds and exerting force on the outer thirds to
push the inner third downward. A fault-bounded ridge is called a horst, a fault-bounded valley is
called a graben.
10. Take a core sample of one of your blocks by twisting a straw as you insert it into the densest part
of the sandwich. After removing the straw, discuss the profile with your group, showing the
pattern of materials (the alternating layers of peanut butter and jelly represent the different
layers of rock). One of the basic rules of geology states that rock layers are laid down horizontally. Discuss with your partners which layers are the oldest and which the youngest in your
model/core sample. Discuss your answers with your teacher and classmates.
Save The Bay’s San Francisco Bay Watershed Curriculum 75
Peanut Butter and Jelly Geology
A Study of Faults and Geologic Activity
FAULT ACTIVITY DEMO SHEET
1. Slowly bend the stack up toward the center;
push in from the edges to mimic folding.
Folding and faulting created the Himalayan
mountain range and many other ranges in
the world.
3. Demonstrate a normal fault by cutting one
of your sandwich stack halves in half and
show the movement of a normal fault. Push
the two blocks against each other and have
one block slide downwards against the
other(normal fault). Then have one slide
upwards (reverse fault) against the other.
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2. Cut the stack in half through the middle,
forming 2 blocks and slide them together
vertically, then horizontally to show strikeslip movements of the Earth’s crust. The
San Andreas Fault has this type of motion.
4. Then cut another of your stacks in thirds to
show the formation of a valley, a graben
fault movement. Push the outer blocks
towards the inner block, forcing the inner
block downward. The Owens Valley is an
expample of a Graben.
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76 Save The Bay’s San Francisco Bay Watershed Curriculum