1. Complete the “Who Dun It” activity at your seat. Be prepared to
Warm Up:
Complete the “Who Dun It” activity at your seat. Be prepared to
explain how you got your answers.
If you have color pencils, get them out
Date
Session
Activity
Page
1/19-20 3
Who Dun It
Dating Rock Layers - Superposition 4
Superposition Challenge 5
Practice…”Which Is Older?” 6
Homework:
Superposition Challenge writing

2. Page 3
Who left:
5th
4th
3rd
2nd
1st
How did you make
your decision?

3. EQ: How do scientists determine the age of rock layers. 8. E
EQ: How do scientists determine the age of rock layers? 8.E.2 Understand the history of Earth and its life forms based on evidence of change recorded in fossil records and landforms. 8.E.2.1 Infer the age of Earth and relative age of rocks and fossils from index fossils and ordering of rocks layers (relative dating and radioactive dating) 8.E.2.2 Explain the use of fossils, ice cores, composition of sedimentary rocks, faults, and igneous rock formations found in rock layers as evidence of the history of the Earth and its changing life forms

4. Why is this statement false: “The caveman had dinosaur for breakfast.”?

5. man and dinosaurs never lived at the same time…how do we know?
Why is this statement false: “The caveman had dinosaur for breakfast.”?
man and dinosaurs never lived at the same time…how do we know?

6. Superposition notes p. 4
Evidence of earths history is found in rock layers. How they are arranged, what is in those layers and any disturbances in those layers tell a story. There are three interpretations we use in determining the age and order of events in rock layers. 1. Relative age 2. Index fossils 3. Absolute age

7. Relative Age: Rock’s age when compared to the ages of other rocks
Relative Age: Rock’s age when compared to the ages of other rocks. Layers of rock that are younger will be deposited on top of layers of rocks that are older. Fossils are the same age as the rock layer in which they are found
This fossil and
this rock layer
are the same age
Highlight the key word in the definition of relative age

8. Index fossils

9. Every fossil is NOT an index fossil
Every fossil is NOT an index fossil. What characteristics must fossils have to be index fossils?
Lived in a large geographic area
(large horizontal distribution of the fossil)
Lived for short period of time
(small vertical distribution of the fossil)

10. Index Fossil A fossil that - widely distributed geographically (large horizontal distribution) - lived for a short period of time (small vertical distribution)
Which fossil is
An index fossil?
How do you know?
What is the
scientific value
of the other fossils?

11. Scientists can use index fossils to show that rocks or geologic events occurring at different locations are the same age. This process is known as Correlation

12. Absolute Age Using the half-life of a radioactive material deposited in rock layers to determine the “exact” age of the rock.
Highlight the most
Important word in the
definition.
Radioactive dating is
accurate on igneous
rocks, but not sedimentary.
Why?
Example:
Uranium (U) decomposes
to become lead (Pb). Its half
life is 4.5 billion years.
What subatomic particle is
responsible for this change?

13. Laws of geologic history
Superposition—Oldest rocks on the bottom of an undisturbed sequence of rock
Original Horizontality—Sedimentary are initially deposited in flat (horizontal) layers
Cross-cutting Relationships—Objects which cross-cut rocks are younger than the rocks themselves (ex: fault or intrusion)
Faults are cracks caused by plate movement
Intrusions are lava that melted through rock and then hardened

14. Superposition

15. Using superposition, label the strata (rock layer) below from oldest to youngest.

16. Superposition Challenge

17. Horizontality
Sedimentary rock layers are originally deposited in horizontal layers

18. Cross-cutting relationships
Faults and Intrusions are always younger than the rocks they cut through.

19. Which is older:
F or S
How do you know?

20. UNIFORMITARIANISM
These laws are based on the assumption that the forces at work today are the same forces at work in history = uniformitarianism.

21. Disturbance in rock layers can be caused by…..
Erosion Tectonic plate movement Volcanic activity

22. a buried erosional surface
What is an unconformity? How does it complicate the relative dating of rock layers?
a buried erosional surface
a part of the rock record
is missing

23. Using the diagram to the left, identify where the unconformity is located by drawing an arrow and writing the word “unconformity” next to it.
What are the characteristics of an unconformity in a rock layer?

24. Superposition Challenge

25. Faults

26. A break in earth’s crust caused by earthquakes
Fault:
A break in earth’s crust caused by earthquakes
(plate movement)
Which is older
A or B
What are the
characteristics of
faults in a
rock layer?

27. Intrusions

28. Lava cuts/melts through rock layers in Earth’s crust.
Intrusion
Lava cuts/melts through rock layers in Earth’s crust.
Which is older
C or B?
What are the
characteristics of
an intrusion in
a rock layer? C

29. Superposition Challenge

30. Overturning

31. Overturning
Horizontal rock layers tilt or fold due to movement of tectonic plates.

32. **** Contact Metamorphism: Metamorphism due to contact with or proximity to an igneous intrusion. This helps you decide if a change in a rock layer was due to erosion (no metamorphism) or an intrusion (intense heat caused a thin layer of metamorphism around the intrusion)

33. “Which is Older?”
For each diagram
write the letter of
the layer/event that
is older

34. Complete Superposition Challenge Diagrams Superposition Extension…writing