LEQ: How do geologists and LEQ: How do geologists and paleontologists determine the paleontologists determine the

relative age of rocks?relative age of rocks?Part 1Part 1

• Key Terms: • Absolute Age, • Relative Age,• Law of Superposition,

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Absolute AgeAbsolute Age

• Turn to page 110-111 in the Earth’s Surface textbook.

• Absolute age is defined as the number of years since an object or organism formed.

• Examples: – Mr. Kraynak is 59 years old.– Mr. Pilsitz is 35 years old.

• In the text box on your notes sheet, create a statement of absolute age.

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Relative AgeRelative Age

• Relative age is defined as the age of an object or organism as compared to other objects or organisms.

• Examples: – Mr. Kraynak is older than Mr. Pilsitz.– Mr. Pilsitz is younger than Mr. Kraynak.

• In the text box on your notes sheet, create a statement of relative age.

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Classifying Absolute VS. Relative AgeClassifying Absolute VS. Relative AgeClassify each of the following statements about

children in a family as either an example of absolute or relative age.

1. Anthony is the youngest.

2. Melony is 4 years old.

3. Michael is older than Amanda.

4. Amanda is 16 years old.

5. Ashley is older than Melony, but younger than Amanda. 44

Children in the FamilyChildren in the Family1. Anthony is the youngest.

Relative Age

2. Melony is 4 years old. Absolute Age

3. Michael is older than Amanda.Relative Age

4. Amanda is 16 years old.Absolute Age

5. Ashley is older than Melony, but younger than Amanda.

Relative Age

Place the children in order from the youngest to the oldest !

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Children in the FamilyChildren in the FamilyCorrect OrderCorrect Order

• Anthony

• Melony

• Ashley

• Amanda

• Michael

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Interpreting SequenceInterpreting Sequence• Read the following story carefully. Then determine the

correct order for the sentences. Be aware that the order has been mixed up!

1. I got out bread, peanut butter and jelly.2. I ate the sandwich.3. I put the two pieces of bread together.4. I spread a layer of jelly on another piece of bread.5. I was hungry.6. I spread a layer of peanut butter on a piece bread.

First _5_, Second _1_, Third _6_, Fourth _4_, Fifth _3_, Last _2_

• How did you determine the order of the sentences? • Geologists apply the concepts we’ve learned and a few

laws of geology to determine the relative age of rock layers. 77

Position of Rock LayersPosition of Rock Layers

• Law of Superposition states that:– In horizontal sedimentary rock layers

• Oldest layer is at the bottom.• Each higher layer is younger than the layer below

it.• Youngest layer is at the top.

• Geologists and paleontologists use this law to determine the relative age of rock layers.

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North Rim of the Grand CanyonNorth Rim of the Grand Canyon

• The following is a picture taken of the north rim of the Grand Canyon in Arizona.

• Observe the picture, and see if you can pick out the different rock layers.

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Supai Sandstone

Hermit Shale

Coconino Sandstone

Toroweap Limestone

Kaibab Limestone

Redwall Limestone

Journal Entry: 1. Which layer is the oldest?Journal Entry: 2. Which layer is the youngest?Journal Entry: 3. Is the Hermit Shale older or younger than the Coconino Sandstone?

Journal Entry: 4. In which layer would you expect to find the oldest fossils?

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North Rim of the Grand CanyonNorth Rim of the Grand Canyon

• Journal entry 1– Redwall Limestone

• Journal entry 2– Kaibab Limestone

• Journal entry 3– Older

• Journal entry 4– Redwall Limestone

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Other “Laws” of GeologyOther “Laws” of Geology

• In part II of the lesson, we will discover the other laws of geology geologists use as other clues to determine the relative age of rock

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