Rock Layers & Relative Age Lab
Steno’s Principles
Background Information: Using Rocks to Determine Relative Age
Estimating when a rock layer formed or the age of certain fossils in those layers is one
of the tasks of a geologist. Nicolas Steno stated four principles that help scientists
determine the order, or the relative ages, of geologic events. Geologists can take core
samples of rock and can tell much about the earth and its life forms by analyzing the
layers in these samples.
Problem: Can the relative ages of rocks be determined by studying the rock layers
and applying Steno’s Principles? Relatively speaking, where were the sea shell fossils
located, how old are they relative to the other rock layers, and what can this discovery
reveal to geologists about the past?
Materials:
*Play-doh (four different colors)
*core sample grid (copied on transparency film or
laminated)
*straws (clear)
*scissors
*sharpie
*cake sprinkles (represent sea shell fossils)
*foil
Procedures:
1.
Carefully flatten your first play-doh color over your grid. It should cover all the squares
but not the numbers and letters.
2.
3.
4.
5.
6.
Repeat until you have a 4 layer high rock. The play-doh should be slightly flattened
together after each layer is added.
Designate 4 boxes (all together in one spot, not random) to embed fossils (cake sprinkles)
into the top layer. Be sure your sprinkles cover the area and are abundant not scarce. List
your coordinates here ___________________________.
Wrap your rock in foil (only one layer of foil thick). Be careful to keep your rock in the
same direction on your grid.
With your sharpie, carefully transfer the grid pattern onto your foil. Write letters and
numbers in each square.
Trade rocks with the group your teacher designates. Do not tell them the location of your
fossils!
7.
8.
9.
10.
You are only allowed to drill for 8 core samples. Drilling is expensive and you only have
funding for 8 drill locations. Plan wisely.
Carefully drill your straw through the rock and pull the entire straw through the bottom.
Cut off the core from your straw and drill through your next location.
Once your team has obtained all 8 core samples, record your data and analyze your
results.
You are to clean up your own rock. Play-doh will be saved. Sprinkles need to be taken
out and thrown away. Do not mix colors. Return to original containers.
Data:
Core Sample Drilling Sites
Location 1:_____
Location 5:_____
Location 2:_____
Location 6:_____
Location 3:_____
Location 7:_____
Location 4:_____
Location 8:_____
Rock Layers (in color label oldest and youngest layers)
Analysis:
1.
List at least 2 of Steno’s principles that helped you determine the relative
age of the rocks and fossils within them. Describe these principles.
2.
Which rock layer is the oldest and which layer is the youngest? How were
you able to determine this?
3.
Where were the fossil shells located? What difficulty did you encounter
finding the fossils? (If you were not able to find the fossils please ask the
other group where they were located. Why was it difficult for you to
locate the fossils?)
4.
What can the discovery of these fossil shells tell geologists about the past?
CORE SAMPLE GRID