Making Sedimentary Rocks!
Summary: Students make a model of sedimentary rock
Materials:
layers to understand how rocks form layers and
represent ancient environments.
For each group:
Source: Windows to the Universe staff member Lisa
 Sand (1-2
Gardiner based this activity on one by
cups)
teacher/naturalist Edith Sisson (author of Nature

Gravel (1-2
with Children of All Ages).
cups)
Grade level: 5-9
 Soil with the
Time: 50 minutes or several class periods
sticks and
 Students will understand that sedimentary
Student
leaves sifted
rocks form in layers over time.
Learning
out or very fine
 Students will understand that different
Outcomes:
sand/silt (1-2
types of sedimentary rock layers
cup)
represent different environments.
 Crushed white
 Students will understand that changes in
chalk (1 cup)
the types of sedimentary rock layers
 Empty halfmean that there were changes in
gallon milk
environments, often because of climate
carton with the
change/sea level change.
top opened up
 Optional:
Seashells or
Lesson Hands on activity or demonstration with
shell
format: participation
fragments,
 5-8: Content Standard A: Science as
National
small fish
Inquiry
Standards
bones
 5-8: Content Standard D: Structure of the
Addressed:

Plaster of Paris
Earth System, Earth History
(about 4 cups
 9-12: Content Standard A: Science as
mixed)
Inquiry
 Water
 9-12: Content Standard D: Earth and
 2 large
Space Science, Origin and evolution of
disposable
the Earth system
cups
 A disposable
spoon or fork
 Fine sand
paper
 Clean up
supplies
(towels, tarp,
newspaper,
plastic drop
cloths, etc.)
DIRECTIONS:
1. Introduction
A. Review what a sedimentary rock is. Review common types of sedimentary
rocks (sandstone, conglomerate, shale and limestone).
B. Have students stack papers on their desk. Ask them which paper got there
first (A: the one on the bottom). Sedimentary rocks form in the same way,
in layers, with the older ones at the bottom.
C. Tell class that during this project they will simulate (or model) what
happens over hundreds of thousands to millions of years as sedimentary
rocks are formed in layers in different environments.
D. Discuss what a model is. (Examples of models: model airplane, dolls,
dinosaur model, video games)
2. Divide students into groups of about 4.
3. For each of the environments in the table below (river, beach, shallow and deep
ocean):
A. Have students describe from their experience what the environment is like.
What sorts of things do they think they would see there?
B. After describing an environment, have student groups choose which of the
materials they would include in their milk carton to represent that
environment (these items are listed in the second and third columns of the
table).
C. Have students fill one of their cups about 2/3 full of the appropriate
sediment and associated fossils.
D. Mix plaster with water according to manufacturer’s directions. Have each
student group fill the remainder of their cup with plaster and stir. Explain
that this is much faster than rocks are actually made. The plaster acts like
the cement that holds real sedimentary rocks together.
E. Have each group put sediment mixed with plaster into their milk carton
and pat it down to form a flat layer.
F. Start the next environment in the table by the same process. Make sure
that student groups do not mix different layers or shake their milk carton.
Mix plaster in small batches (one for each environment) to avoid it drying
too quickly. For the limestone layer, mix plaster a little more watery than
usual because chalk will absorb water. The plaster of the first layer does
not need to be dry before adding the next. If it is really soupy, sprinkle a
little dry plaster on the top before adding the next layer.
4. After plaster has dried (about 20 minutes), take the layers of sedimentary rock out
of the milk carton. (You may need to rip the milk carton off!)
5. Have student groups rub it lightly with very fine sand paper and draw what the
layers of "rock" look like in their notebook (noting colors, textures, and other
features in the margins of their picture). Show them images of real rock layers
from places like the Grand Canyon, southern Utah, or something closer to home.
ASSESSMENT:



If your class has already covered types of sedimentary rocks, ask students to
identify the types of sedimentary rocks present in their model, even though they
are not real.
Ask students to recall which types of environments each rock type represents. If
the environment in this one spot changed over time from a river to a beach to a
shallow ocean to a deep ocean what must have happened? Sea level rise!
Extension: Have students be paleontologists and dig for fossils in the layers of
rock. Where would you expect to find the most clamshell fossils? Fish fossils?
Use picks, chisels and small hammers to find them.
EXTENSIONS:
Have students be paleontologists and dig for fossils in the layers of rock. Where would
you expect to find the most clamshell fossils? Fish fossils? Use picks, chisels and small
hammers to find them.
BACKGROUND INFORMATION:
Sea level changes can be caused when either the land level sinks (called subsidence) or
when the water level rises, or when both processes are happening together. Water level
can rise because glaciers melt, adding water to the oceans, or when plate tectonic
movements shallow the ocean basins displacing water onto the edges of continents. It is a
natural process that has gone on since there have been oceans on Earth!
This activity works best when students have already reviewed types of sedimentary rocks
(conglomerate, sandstone, shale, and limestone). Note that the same rock types can form
in several different environments. This is a good topic of discussion, especially if
students recognize that the soil is potting soil found on land. Shale that forms in swampy
floodplain areas can look very much like shale that is from the ocean floor or even shale
from a lake bottom. Fossils are a good way to tell the difference. Similarly, sand dunes
formed in the desert are made out of sandstone just like the beach sand (and not all
beaches are made of sand). One must be a detective to figure out what past environments
were like!
For a shorter demonstration version of this activity, omit the plaster and milk cartons and
tell students the story of changing environments as you add layers of sediment and
"fossils" to a rectangular fish tank (or any container that you can see through). They are
able to see the layers right away, although the connection to sedimentary rocks might be
more of a challenge.
Table of Environments:
Environment
Type of
Sediment
Biological remains you
might find there
Rock type
produced
River
Pebbles
fish, plants
conglomerate
rock
Beach
Sandy
shells, seaweed
sandstone
Bottom of the
shallow ocean
Silt/mud
shells fish
shale
Bottom of the deep
ocean
Crushed white
chalk
few shells, fish
limestone