Relative Age Dating
By Nancy Volk
Law of Superposition
One of the fundamental laws of archaeology is the Law of Superposition. The law
states that sedimentary layers are deposited in a time sequence, with the oldest
on the bottom and the youngest on the top.
Weathering and Erosion
When a rock layer is not parallel and smooth but appears irregular (see the
interface between layers C and D), then erosion and weathering occurred and like
a big eraser removed part of the history of the rock layer. We compare the rock
layers to other areas to try and find clues to the missing evidence. The rock layers
below show this abnormality.
VOCABULARY
Anticlines
Faults
Folds
Igneous
Law of Superposition
Sedimentary
Synclines
HELPFUL TERMS
Absolute age dating
Fractures
Lava
Magma
Monocline
Relative age dating
We still know the youngest to the oldest. What is the order?
Sequence
What type of rock creates layers?
What About Igneous Rocks?
When an igneous activity comes into play in an area with sedimentary rock
layers it can push through the cracks of layers making interesting formations.
When an igneous activity occurs it is always younger than the rocks it moves,
flows through or erupts over. Think about this and see if this makes sense!
Inside This Packet
Relative Age Dating
1
New York State Standards
1
Activity: Layers
2
Demonstration/Activity:
Rock Layers
3
Paper Block Printouts
4-7
New York State Standards
Middle School Activity
Standard 1: Analysis, Inquiry, and
Design
What is the order of oldest to youngest rock layers?
Earth Science - Prior Module 4
Middle School
Standard 4: Physical Setting
Key idea 2.1c, 2.1f, 2.1g, 2.1h, 2.1i,
2.2a, 2.2c, 2.2g
Page 1
Demonstration: Age Dating
MATERIALS NEEDED
Canning jar and lid
Food coloring
Modeling clay
Scissors
Tape
Wax paper
What to do:
1. Take the glass canning jar and fill it about 1/3 full of sediments that are
multi-sized particles.
2. Fill the remainder of the jar with water. Cover tightly and add electrical tape
around the perimeter of the lid area to add more security.
3. Shake vigorously.
4. Allow the sediments in the jar to settle for several days. Notice what occurs
to the sediments as they are deposited.
5. The students should be able to see layers of sediments settling out from the
stirred water. Discuss how this happens in locations on earth in streams, ponds,
lakes and oceans.
Students should
be able to:
Identify layers of deposition
Describe the relative ages
of sedimentary layers
Earth Science - Prior Module 4
Middle School
Page 2
Demonstration/Activity: Rock Layers
MATERIALS NEEDED
Modeling dough
(recipe provided)
Plastic knife
Wax paper
Using modeling dough (recipe provided below) add three different colors to make
three different rock layers. Have students roll out three different layers and place
them on top of one another. Have them create anticlines, synclines and describe
how they made these. Have them discuss how this is like the forces in the earth
causing rock layers to bend and fold. They can explore ideas about faults with the
use of a plastic knife as well. Have the students work with the modeling dough on
top of wax paper for easy cleaning.
Paper block printouts
Tape
Modeling Dough Recipe
1 cup flour
1. Mix flour, salt and oil, and slowly add the
water.
1/2 cup salt
2. Cook over medium heat, stirring until
dough becomes stiff.
1 cup water
3. Turn out onto wax paper and let cool.
2 tablespoons oil
4. Knead the modeling dough with your
hands until of proper consistency.
2 tablespoons cream of tartar
Students should
be able to:
5. Divide the recipe into three portions
coloring each one a different color.
Explain the Law of
Superposition_
Explain the difference between
sedimentary and igneous rock
layers
After explaining the notes to the students, have them cut out the perimeter of the
paper block printouts provided. Using tape, put the blocks together to show a 3D
form of rock layers cut out of a piece of land.
1. Ask the students to identify the youngest and oldest rock layer in each block.
2. They should be able to share why they chose these.
3. They should be able to explain any abnormalities in the layers.
Earth Science - Prior Module 4
Middle School
Page 3
Paper Block Printout #1
A) Law of Superposition
Model #1
Earth Science - Prior Module 3
Middle School
Page 4
Paper Block Printout #2
A) Law of Superposition
B)Weather/Erosion
Model #2
Earth Science - Prior Module 3
Middle School
Page 5
Paper Block Printout #3
x
x
x x x x
x
x
x x
x x
x
Earth Science - Prior Module 3
Middle School
x x
,n ,n
,
n
,n
,n ,n ,n
,n
,n ,n ,n ,n
,n ,n ,n ,n ,n
,n ,n
,n
,n ,n
,n,n
,n
,n ,n
n
,
,n
n
,
n
,
n
,
n
,
n
,
,n
n
,
,
n
,n
,n ,n
,n ,n ,n ,n
,n
,n
x
x x x
x
,n ,n ,n ,n
n
,
w
wwwwww w
x
wwww
www
w
w
x
w
w
w
w ww w w
x x
ww ww
x x
www ww w w
x x
ww
www
w
w
w
w
x
www
w
w
x
x
w
ww
x
x x
w
x
x
x
x
x
x
x
x x
x
x x
x
x x
x
x
x
x
x
x
x
x
x x
x
x
x
x
Model #3
x
x
x
x
x
x
x x
x x x
w
w
x
ww w
wwwwww w x
x
w w ww
www ww w w
x x
w w ww
wwwww w www x x
x x
wwwwwwww w
x
x w w w n,
n,
x
x x x
n, n, n,
,n ,n ,n ,n
x
n, n, n,
,n ,n ,n ,n ,n
n, n, n, n,
,n
,n,n ,n
,n ,n
n, n,
n, n, n,
,n
,n
,n
n, n,
,n ,n
n
,
,n
n,
, , n,
n, nn
,n ,n ,n ,n
n,
n, n, n,
,n ,n ,n
,
n, n, nn
,n
n
,
,
,n ,n
n,
n
,
n
,
,n ,n
n,
n, n, n,
,n
,
n, nn
,
A) Law of Superposition
B) Igneous intrusion/extrusion
x
w w ww
x
w wwwww
ww w w
x
x
x
x
w
w
wwww w w
www
x x
x
ww w w w
x
w wwww w
ww w w
ww
,n ,n ,n
x x x x x
,n ,n
,n ,n ,n ,n ,n
,n ,n ,n ,n ,n ,n ,n
,n ,n ,n
,n ,n
,n ,n
,n ,n
,n
,n,n ,n ,n
,n
,n
,n
x
x
x
x
x x
x x
x
x
x
x
x
x x
x
x
x x
x
x
x
x
x
x
x x x
wwwwww
x
w ww www
w
w
www
w ww wwww
ww
x ww wwwwwwww ww
w
w
www wwwwwwww
ww w www
x x
x
x x
x x
x x x
x
x
x
x
x x
x
x x x x
x
x
x x
w wwww
x
ww w
www
ww www w www
w wwww x
x x
w
x
w w w ww www w
www w ww x
w
x x
x
x
x
x
x
Page 6
Paper Block Printout #4
A) Law of Superposition
Model #4
Design Your Own Model
Earth Science - Prior Module 3
Middle School
Page 7