Lab Activity: PBJ Geology Rocks
Version 2- student directed
Objective: Simulate the history of various geological formations by building layered sandwiches.
Using various types of bread and fillings to model: sedimentary rock, fossils, core sampling, anticline,
syncline, faulting, uplift, and a subduction zone, students will create a “sandwich” of earth layers.
jelly (squeeze bottle is best)
chocolate chips or raisins (optional)
candy worms or candy fish
peanut butter- chunky (may substitute marshmallow fluff especially if a student has peanut allergy)
tablespoon for measuring peanut butter/jelly
Note- Each lab table makes one earth layer sandwich.
* one per each lab group
Students pretend to be geologists and use a plastic straw or a section of small-diameter plastic pipe to take a
“core sample” of the layers. Have the students examine the core and identify the layers. Relate this to real core
samples that help
determine the composition and historical sequence of the Earth’s formation.
Students will bend and “fold” the sandwich to relate this model to the formation of mountains as plates collide.
Later they will cut their sandwich in half and force one half to “subduct” under the other. Students visualize
the interior layers of mountains, documenting how the order of layers can change. After creating a subduction
zone, students take another core sample and compare the results.
PBJ Geology Rocks LAB
Name ______________________ date ____________
Objective: Simulate the history of various geological formations by building a layered sandwich. This will
model sedimentary rock, fossils, core sampling, anticline, syncline, faulting, uplift, and a subduction zone.
___ one paper plate ___ one plastic knife
___ one slice white bread ___ one slice wheat bread
___ one slice dark bread ___ one tablespoon or squeeze of jelly
___ two pieces of paper towel ___ one plastic straw
___ chocolate chips or raisins (optional) ___ candy worms or candy fish
___ one tablespoon peanut butter- chunky (may substitute marshmallow fluff )
Note- Each lab table makes one earth layer sandwich.
Read the following story to help your lab group build a geologic sandwich.
White sand erodes from upper rocks and them downstream. Again, the velocity of the water
is transported by rain, melting snow, and slows as the river widens and the silt gradually
gravity into a flowing stream to the foot drops to the bottom. This eventually forms a
of a mountain. The sand is carried along sedimentary rock called shale. Third layer –
the stream into a river that eventually Add a slice of wheat bread for the shale.
widens, causing the flow of the water to
slow down. This allows the white sand to Meanwhile, glaciers are melting on the
drift slowly to the bottom. Over many Earth causing the ocean to rise and cover
years, this sand becomes cemented the area. Millions of tiny marine organisms
together, forming a layer of white sandstone. and shells begin to line the ocean floor. After many
Use a slice of white bread for this first layer of years, the ocean recedes and shells have cemented
white sandstone. together forming a layer of rock
called limestone. Fourth layer – Use the plastic
A hurricane passes through the area, knife to spread jelly (limestone) on the wheat
bringing torrential rains and wind. Trees, bread. Many fossils can be found in this layer. Add
rocks, dirt, and gravel erode into the candy worms or fish to the jelly.
water and cover the white sand. Second
layer - Use the plastic knife to spread chunky Finally, a layer of brown sand is blown over the
peanut butter or marshmallow fluff, on the entire area. There has been a severe drought and
white bread. You may add chocolate chips or mighty winds have sandblasted large, brown
raisins to represent the eroded materials. boulders with small bits of rocks. In time this
layer will become brown sandstone. Sixth layer –
Over many years, the river erodes brown Add a slice of dark bread for the brown
silt particles of clay from the land and carries sandstone.
The geologic sandwich is now complete! Follow the PBJ Geology Rocks directions to complete the lab.
After building your geological sandwich and taking a core sample, sketch and label what your core
sample looks like in the box below.
When geologists study rocks, they rarely find them flat and horizontal. Often they will see layers that
are bent or broken. To illustrate these structures gently bend your sandwich to form a hill. (Keep the
oldest layer on the bottom.) Sketch and label your hill in the space provided.
This is called an ANTICLINE.
Now, bend your sandwich to form a trough. (Bend it in the opposite direction than you did for the
anticline.) Sketch and label your trough in the space provided.
This is called a SYNCLINE.
Mountains and valleys are formed this way.
Sometimes the crust of the earth moves up or down as it pushes into other pieces of earth at a
subduction zone. In part, this movement causes earthquakes. Cut your sandwich in half and move one
half up or down.
Hold the two halves up in front of you. Which side moved up or down? Make sure to force one half to
“subduct” under the other half.
Sketch your sandwich now, showing the movement up or down. (Either the left side moved up or the
right side moved down or the other way around. You can see this movement because of the different
layers of the sandwich.)
This is demonstrates the uplift of mountain building along a convergent boundary.
Now use the straw to take another core sample through the thickest part of your model.
Sketch and label the core sample in the box below.
Subduction Zone Core Sample
Use the space below to describe how this core sample is different from the first core sample you took.
Remember to explain some of the geological process that produced the changes.