Rock Layers Lab
Name: __________________
4th grade PSI Science
-----------------------------------------------Experiment Questions
How are different sediments deposited differently?
How do sedimentary rocks form?
Before You Begin
Do you think that all sediments settle to the bottom of a liquid
in the same way? Why or why not?
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What do you think makes rock layers different from one
another? How might the sediments in different layers be
different from each other?
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Purpose
During this experiment, you will observe sediments sinking to the
bottom of water. This simulates deposition, the first step in
sedimentary rock formation. You will then create a model of a
sedimentary rock, using the information you have learned about
sediments and how they are deposited. In nature, sedimentary
rocks do not form quickly; it is a process that happens over
hundreds of thousands to millions of years. In this experiment,
you will simulate this process in a few days to find out more about
sedimentary rocks and the process of their formation.
Materials (for each station)
 gravel
 sand
 top soil
 graduated cylinder
 water
 spoon
 stopwatch / timer
 small bowl
 plastic water bottle, cut in half (bottom half)
 watered-down white glue
 toothpicks
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Procedure
How Sediments Settle
1. Observe the clay, gravel, and sand that you have. Record
notes about the different sediment sizes on the Sediment
Characteristics table below. (You may try to trace a piece of
sediment, or measure it, or you may comment on its size in
relationship to the other sediments.
2. Fill the graduated cylinder about 3/4 full of water.
3. Drop a small spoonful of one type of sediment into the water;
observe it as it falls. Write short notes about your observations
in the observations column on the Sediment Characteristics
table.
4. Drop another small spoonful of the same type of sediment into
the water; use the stopwatch to time the length of the fall.
Record the times in the settling rate column on the Sediment
Characteristics table.
5. Repeat steps 3 and 4 with the remaining two sediments.
Hypothesize: What do you think will happen if you pour a
mixture of the three types of sediment into the water?
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6. In a small bowl, mix together three spoonfuls of each sediment.
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7. Pour the mixture into the water. Observe closely as the
sediments fall. Record the settling order in your data table,
using 1 to indicate the sediment that settled first.
SEDIMENT CHARACTERISTICS
sediment
type
sediment
size
observations
settling
rate
settling
order
clay
gravel
sand
Did the three sediments settle in the same order when
dropped in the water together as they did when dropped in
separately? Why do you think?
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4th Grade PSI Science
History of Planet Earth
Sedimentary Rock Model
1. Pour a few spoonfuls of the sediment you found to settle the
fastest (#1 in the settling order column) into the water bottle.
This should be enough sediment to form a good layer in the
bottom of the water bottle (about 1-2 cm).
2. Pour a few spoonfuls of the sediment you found to settle slower
(#2 in the settling order column) into the bottle on top of the first
sediment.
3. Pour a few spoonfuls of the sediment you found to settle the
slowest (#3 in the settling order column) into the bottle on top
of the other two sediments.
4. Pour the glue mixture gently into the bottle of sediments,
making sure to cover the top layer of sediment but using as
little as possible to do so.
5. Leave the bottle to sit for one day, preferably in a warm, dry
place.
6. After one day, use a toothpick to gently test the hardness of
your rock. Observe your rock closely. Draw a picture of what
you see in the box labeled Day 1.
7. Let the “rock” sit and harden another day. Observe your rock
closely. Draw a picture of what you see in the box labeled Day
2.
DAY 1
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DAY 2
4th Grade PSI Science
History of Planet Earth
Lab Questions
1. What happened to the glue solution after two days?
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2. What does the glue solution represent?
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3. What happened to the sediment layers after two days?
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4. Which layer was the first to harden?
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Conclusion
1. How is this sedimentary rock model is similar to the natural
processes involved in the formation of sedimentary rock
layers?
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2. How is it different?
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4th Grade PSI Science
History of Planet Earth
TEACHER NOTES
This lab is best done in small groups. The number of students in each group can vary
depending on various factors. Every group will need all the materials for the lab.
If possible, students can try to remove the water bottles from the sediments after a day
of sitting, leaving a more true “rock”.
Note: you may want to poke a few small holes in the bottom of the water bottles before
students begin making their rocks, as this will allow air to flow in and dry out the glue
from both directions.
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Answer Key
Answers to the Lab Questions:
1. What happened to the glue solution after two days?
Over two days, the glue solution seeped through the layers of the sediment
in the bottle and hardened.
2. What does the glue solution represent?
The glue represents the mineral cements that hold sedimentary rock
together.)
3. What happened to the sediment layers after two days?
The sediment layers dried out and hardened after two days.
4. Which layer was the first to harden?
The top layer should have hardened first.
Answers to the Conclusion Questions:
1. How is this model is similar to the natural processes involved in the formation of
sedimentary rock layers?
Different sized particles settle out at different rates.
Time is needed for the sediment to dry out.
A cement is needed to hold the particles together.
2. How is it different?
We did not model the pressure that compacts the sediments.
In nature the cement is formed from salts left after water has been
squeezed out of the sediments.
Our experiment only took two days, while it usually takes many years.
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