Warm Up – December 6On a separate piece of paper

Warm Up #27 – December 8

• Describe what a paleontologist does• Describe the different types of fossils

Finding the Relative Age of Rocks

Questions

• What are the relative and absolute ages?• What is the law of superposition?• What are unconformities?• What are faults intrusions and extrusions?• How are fossils used to date rocks?

• The relative age of a rock is its age compared to the ages of other rocks.– It is like comparing your age to someone else’s

• The relative age does not provide its absolute age

• The absolute age of a rock is the number of years since the rock formed.– It is difficult for geologists to determine the

absolute age

• The law of superposition states that in horizontal layers of sedimentary rock, each layer is older than the layer above it and younger than the one below it.

http://thehappyscientist.com/blog/science-photo-day-468

• Unconformity is where an old eroded surface is in contact with a new rock layer.

• Faults can occur only after rock layer have formed; therefore rock layers are older than the faults

• Igneous rocks that have formed as magma and cool underground are called intrusions

• Extrusion are volcanic, molten materials that cool and harden when they reach the Earth’s surface

1. What is the youngest rock layer on the figure? (A,B,C,D)

2. Is the extrusion older or younger than layer B? A)Older B)Younger

3. Is the fault older or younger than rock layer A? A) Older B)Younger

1. The number of years since a rock formed

A. absolute age B. relative age C. law of superposition D. index fossil

2. A break or crack along which rocks move

A. UnconformityB. IntrusionC. extrusionD. Fault

3. The way to determine relative age of rocks

A. relative age B. Absolute age C. law of superposition D. index fossil

4. Harden layer of magma1. Fault2. Intrusion3. Extrusion4. Law of superposition

5. The age of rock compared to the age of other rocks

A. absolute age B. relative age C. law of superposition D. index fossil

6. A place where an eroded surface is in contact with a new layer

1. Unconformity2. Law of superposition3. Relative age4. fault

7. Fossils used to determine the relative age of rock layers

1. Trace fossils2. Mold fossils3. Preserved fossil4. Index fossils

8. Harden layer of lavaA. UnconformityB. IntrusionC. extrusionD. Fault

Finding Clues to Rock LayersPage 118

• Problem– How can you use fossils and geologic features to interpret

the relative ages of rock layers?• Procedure (complete 1 and 2 – don’t have to have

complete sentences)1. 2.

• Analyze and Conclude (answer all questions in complete sentences)– Site 1 (1-5)– Site 2 (6-9)