1. Dating Differences Defined
Absolute vs. Relative Dating

2. Relative Dating
A method of determining the age of a fossil by comparing its placement with that of fossils in other layers of rock

3. Absolute Dating
Any method of measuring the age of an event or object in years

4. Activity – Model
List 5 important events in your life (the one at the bottom should be the oldest!!
Started working at Wendell Middle
Started working at Southwest Middle
Graduated from Southeastern University
Started work at Lakeland High School
Graduated from high school
Got Braces
Born
December 2014
August 2013
May 2013
January 2013
June 2008
September 2004
November 1990

5. Radioactive dating
Measurement of the amount of radioactive material (usually carbon 14) that an object contains; a form of absolute dating

6. Uranium
A white, radioactive metallic chemical element that weighs more than any other element in nature; used in radioactive dating

7. BrainPop
See how radioactive dating works by watching this brainpop: Carbon Dating

8. 8th Grade Science Spring 2015
Rock Layers
8th Grade Science
Spring 2015

9. Rock Layer
The four rock columns were found at the places indicated by letters A, B, C, D. Different rock layers are found on the surface at these places.  The problem is to find which layers match.
Color the matching sections from A, B, C, and D the same color.
Cut out the columns of rock layers.
Arrange the columns of rock layers side by side by matching layers.

10. Do not write what is in purple or teal
Write the following notes on the BACK of your Rock Layers Activity
Title: The Law of Superposition

11. The Law of Superposition
8th grade science
Spring 2015

12. Law of Superposition
States that the oldest rocks lie on the bottom and the youngest rocks are on top of any undisturbed sequence of sedimentary rocks.

14. Correlation
Matching rock layers in different locations to see if they formed at the same time and under the same conditions

15. Unconformity A gap in the rock record
What could cause an unconformity?
Erosion could cause rock to be worn away and “disappear”
When plates move together (convergent boundary) one plate “disappears”

16. Rock Layers Analysis Questions
Flip back over to the Rock Layers side and answer the following questions on that side.
1. Which rock layer is the oldest? The youngest?
2. Which fossil is the oldest? The youngest?
3. What happened to the layer in rock strip C? (Where did it go?) Use your vocabulary words to describe what happened to layer in rock strip C.

17. Sedimentary Rock Most fossils are found in Sedimentary Rock
Rock that forms when sediments are compacted and cemented together

18. Index Fossil
A fossil of an organism that is known to have lived in a particular geologic age that can be used to date the rock layer in which it is found
A key example of an organism used as an index fossil are TRILOBITES, a group of hard-shelled animals whose body had three sections, lived in shallow seas, and became extinct about 245 million years ago

19. Other Clues to Relative Age
Clues From Igneous Rock
Lava that cools at the surface is called an extrusion
Rock below an extrusion is always older.

20. Magma that cools beneath the surface is called an intrusion
An intrusion is always younger than the rock layers around and beneath it
Extrusion
Intrusion

21. The Cross-Cutting Law
Faults (a break in the rock) are always younger than the rock it cuts through!
Fractures (a crack in the rock) are always younger than the rock it cuts through
The arrow points to a fault – notice the layer of white rocks do not line up with each other

22. To Summarize
Generally, the top layer is the youngest – bottom layer is the oldest
The rocks below an extrusion (lava at the top) are always older than the extrusion
The intrusion (lava within the rocks) is always younger than the rocks around it
A fault is younger than the rocks around it

23. Using your knowledge of the Law of Superposition, put the following layers in order from the youngest to the oldest. E
YOUNGEST _______
_______
OLDEST _______ D A B C

24. Practice
You have two other examples on your worksheet – try to put the rock layers in order from youngest to oldest

25. Items to STUDY for Tomorrow’s Quiz
Examples of Mechanical and Chemical Weathering
Vocabulary Definitions:
Relative Dating, Absolute Dating, Radioactive Dating, Uranium, Correlation, Unconformity, Sedimentary Rock, Index Fossil
Law of Superposition
Where are the oldest/youngest rock layers?
What are intrusions, extrusions, faults and fractures?